LAMINATE TOOLS TUTORIAL

Transcription

1 LAMINATE TOOLS TUTORIAL

2 Laminate Tools Tutorial 2/62 Anaglyph Ltd

3 C O N T E N T S Introduction... 5 The basics... 5 Model control...6 View modes...6 Model description... 8 Draping Create a Material...10 Create a Ply...10 Save the model...12 Change to another mesh Sets definition BottomSkin element set Select the Bottom Skin...14 Verify and correct...14 Remove undesired elements...15 Finalise the set definition...16 Channel element sets Holes element set Other element sets Materials definition Detailed Ply definition Create a ply Pick the surface...22 Define the fibre direction...23 Aspects of the ply Rotate the ply by Create ply over channels Draping tubes Refine the original plies Review all Plies Create a Layup Offset definition Laminate generation Static Analysis Post-processing Stresses Failure calculations Global Ply sorting Interactive calculations Final design Manufacturing Concluding Remarks Laminate Tools Tutorial 3/62 Anaglyph Ltd

4 Laminate Tools Tutorial 4/62 Anaglyph Ltd

5 Introduction The present document illustrates the use of Laminate Tools, through a detailed tutorial. You will require Laminate Tools version 3.3 or later to properly follow the steps in this tutorial. This document is accompanied by several files on hard disk, CD, or zip format (depending on source) which are saved collectively in a folder named Tutorial. Begin by launching the application from the Start menu. Notice that the start-up banner briefly shows which modules are active. The present tutorial assumes that all modules are active, so remember that if your licence is only partly activated, you will find that certain steps in the tutorial will not work. For the purposes of the tutorial we will be using a simple model that will demonstrate most features of Laminate Tools in a series of steps. In the interests of training in the use of the software itself, we will occasionally take actions that do not make good sense from a structural design point of view. Laminate Tools can read structural meshes composed of triangles and rectangles (thin shells), which have been prepared by other software. Typically, an FEA pre-processor is used to prepare the mesh (from the original geometrical surfaces), and this is then saved in a format suitable for use with Nastran or Ansys, but also with Laminate Tools. Alternatively, the structural surfaces are prepared in a CAD system and are then translated into triangular "elements" in a format known as Stereolithography (.STL) which can then be brought into Laminate Tools for the purpose of simulating the draping of composite fabrics. For the present tutorial our model has originated in a CAD application. The easiest route from CAD to Laminate Tools is to convert the model to the.stl format, which is a simple process. This has already been done in preparation for this tutorial, so we proceed now by reading the file Tutorial.stl (which can be located in the Tutorial folder) into Laminate Tools, using the File/Open menu. The basics When a file is first loaded, three windows appear by default: a Data window on the left displays a hierarchical breakdown of the model contents, a Model window that graphically displays the model occupies most of the screen and an Info window along the bottom gives summary reports and interactive feedback. If for any reason these windows are resized or moved, their default layout can be restored with the menu command Window / Optimise Layout. Additional graphics windows may be created with Window / New Model Window. Laminate Tools Tutorial 5/62 Anaglyph Ltd

6 Model control Use the toolbar icons: (front, rear, top, bottom, left, right, Isometric 1 to 4). to view the model from predefined view directions In addition: Rotate the model: Ctrl + click Middle mouse button on the Model window and drag. Move the model: Shift + click Middle mouse button and drag. Rotate the model around an axis normal to the screen: Shift+Ctrl + click Middle mouse button and drag. Zoom in/out at the point where the pointer is: scroll the mouse Wheel. Alternatively, use each of the toolbar icons: with the Middle mouse button to rotate, pan, and zoom. Furthermore, a 3Dconnexion device such as SpaceNavigator may be used for model manipulation. Just make sure the device is connected to the computer when the application is launched. Note that the above mouse and key combinations may be customised in General Preferences, as discussed later on. Also that the alternative fly-by view mode manipulates the viewpoint rather than the model. This has the advantage of perspective and the ability to view from inside a hollow object. View modes Edges view mode: Shows free edges (brown) and branches (purple). This is essentially an outline of the model where the graphics are not cluttered, but most importantly it is used for confirmation that there are no undesirable free edges (disconnected elements, resulting in gaps or cracks). Wireframe view mode: Shows all elements, including hidden lines Laminate Tools Tutorial 6/62 Anaglyph Ltd

7 Hidden lines view mode: Does not show hidden lines Smooth shaded view mode: Hidden line mode with realistic lighting effects. Custom Settings view mode: Open the Plot Options window / Custom Views tab and select the desired model features to view: Laminate Tools Tutorial 7/62 Anaglyph Ltd

8 The program menus by default follow the standard Windows layout of File, Edit, View, etc. The tutorial uses this layout but users may prefer to use an alternative module-based layout in the future, as selected in the File/General Preferences window: This window is also used to control a number of other general user preferences. The most important ones to note at this stage are: The Show Ply Coverage Filled and Shaded option helps with ply visualisation. The Custom Colours... button can be used to produce better-looking graphics both for screen and printout, and standardise across a workgroup or company. This document has been produced mostly with colours set to default values, with some variations later on. The Keyboard & Mouse... button can be used to customise the keyboard and mouse buttons for graphics manipulation. The Workstation Options define which files are registered with the operating system to open automatically with Laminate Tools. The Disable 3Dconnexion device support option should be checked if no such device is used, to speed up the application startup procedure. Model description The model consists of : 1. A simple curved surface, which is part of a cylindrical surface. Laminate Tools Tutorial 8/62 Anaglyph Ltd

9 2. A flat portion which is part of a circular surface. 3. A raised section along the bottom, with tapered sides. Foam will be introduced later between the cylindrical section and this raised section to create a sandwich. 4. Two U-channel sections that follow the same curvature as the surfaces they are connected to. Their top surfaces result in double curvature and will provide a typical draping condition. In addition, they will be used to demonstrate how to drape tubular surfaces. 5. Two elliptical outlines are defined on the cylindrical surface and are filled with elements, but these will be "removed" in later steps to demonstrate draping around holes. Laminate Tools Tutorial 9/62 Anaglyph Ltd

10 Draping Create a Material As an initial exercise, we will create a simple Ply. A Ply is a piece of fabric that covers part of our structure. To create one, we first need to create a Material: Select the menu Edit / Create Material..., or right-click with the mouse on the tree node and select Create Material... The Material Properties window appears. On the left, enter: Name: Fabric Type: Draped (Scissor) Nominal Thickness: 0.2 Maximum Strain: 25 Warp/Weft Angle: 90 All units defined within Laminate Tools are in the units the model is defined in. We already know that the geometry has been specified in mm, so thickness is also given in mm here. Click on. Note: the Draped (Scissor) type of material simulates fabric in which the warp and weft directions rotate relative to each other as the fabric deforms over a curved surface. Create a Ply We can now proceed with the creation of a Ply that uses this material. Select the menu Edit / Create Ply..., or right-click with the mouse on the tree node and select Create Ply... The Ply Properties window appears. In the Basic tab: Name: Ply_001 Type: Draped (Scissor) Material: Fabric To help with visualisation, select the Custom Settings view mode, and set the background colour to white (in the Plot Options window, see above). Then view the model from the Bottom ( ), zoom so that the entire model is visible, click on, select by Rectangle...+ (all other options remain unchanged, such as Visible Elements only ticked, mode Replace, etc.), click and hold the left mouse button around the top-left corner of the Model window, drag to form a rectangle that includes the entire model, and release the mouse button. Laminate Tools Tutorial 10/62 Anaglyph Ltd

11 This procedure will result in the selection of all the elements that are visible from the bottom of the model. The selected element IDs appear in the Elements field of the Ply Properties window. If you fail to complete this step properly, start again by first clicking and selecting Clear element ID's. Now we have defined the desired coverage for our Ply. Next, we need to define the position and direction of how we will apply the fabric onto the structural surface. Click on then left-click and hold somewhere close to the centre of the ply coverage, drag to the right (along the global X direction) and release. As a result, we obtain two vectors: one that defines the direction from which the ply fabric is brought onto the surface (Application Direction), and one that defines a Reference Direction for the fibre (warp) orientation at the point of application (Start Point). If you fail to complete this step properly, start again by first clicking and selecting Clear Vectors. Now we set the Reference Angle in the Ply Properties window to 0, thus defining our warp direction to be aligned with the Reference vector defined above. Finally we click on to commence the draping simulation process. The result will be a calculation of the way warp and weft fibres deform to cover the surface. To best visualise the created ply, select the Edges view mode, the Isometric 3 view direction and depress the Ply toolbar icons as follows:. This combination will display the vectors, the draped pattern (fibre directions in-place) and the flat pattern (fabric outline to cut). Having created one ply, we can easily create the next one. Simply change the Ply Name to Ply_002, change the Reference Angle to 45 degrees and click on again. The result is a second ply orientated at 45 to the first one. These plies now appear in the tree in the Data window, sorted alphabetically: Clicking on a Ply name makes the Model window display the Ply's selected attributes (as set in the Ply toolbar) and also makes the Info window display a detailed report of the ply definition and draping results (min/max shear angles, min/max thickness achieved). Laminate Tools Tutorial 11/62 Anaglyph Ltd

12 Save the model Now we can save our work through File/Save As... We specify Step1 for filename and hence save as Step1.Layup. Leave all other controls with their default values. The.Layup format is the data file of Simulayt s Layup Technology, used in Laminate Tools as well as in embedded products like MSC.Patran Laminate Modeler. This provides a seamless data transfer between design, analysis and manufacture. It contains all the composite material related information, as well as the model mesh. Having saved our work, we can close the file with File/Close. Change to another mesh We have demonstrated how to bring CAD data into Laminate Tools and how to create simple plies. Before we explore more complex ply definitions, we will address a problem that might not be initially apparent. What would happen if, having defined dozens or hundreds of plies, the model is completely remeshed for some reason, or even the geometry is slightly modified resulting in both shape and mesh changes? Would we have to redefine all our plies from scratch using the new mesh? Thankfully not, because Laminate Tools provides the command File / Import > Layup from.layup file(s)... which is used to specifically import plies and layup from earlier work, which do not need to be on the same mesh, or even shape to a certain degree. Let us therefore abandon the triangular mesh that originated in the Tutorial.stl file and from this point on use a mesh that has been created with Femap (a UGS product) for FEA purposes: Mesh.nas, which contains a Nastran mesh of quadrilateral and triangular elements that define the walls of our thin-shell component. In fact, it also contains many tetrahedral elements used to define the sandwich foam core, but these elements are ignored by Laminate Tools. Other information that is ignored includes boundary conditions and applied loads. The same information also exists in the form of Mesh.cdb, which contains an identical mesh in Ansys format. Therefore, proceed now by selecting File/Open to read the file Mesh.nas (Nastran users), or Mesh.cdb (Ansys users). The two plies we created earlier can now be imported onto the present mesh by using File / Import > Layup from.layup file(s)... Note that multiple files may be selected here, in case plies were created in separate files by a team of people working independently, or separated for reasons of clarity, component variations, etc. In our case there is only Step1.Layup, so we select it, click on Open, and leave all the import parameters at their default values. If you wish to enquire the meaning of these parameters, hit F1 and the online help will display the relevant topic. When we finally click on OK, Laminate Tools will take a short while to analyse the two meshes, match them and recreate our 2 plies. Once completed, we can preview Ply_001 and Ply_002 as previously. If elements are incorrectly matched as a result of the import, we will have to make manual corrections. Under the branch, we now see 3 materials: Fabric has been imported from the Step1.Layup file, but mat1.1 and mat1.2 have originated from the Mesh.nas file (MAT.1 and MAT.2 from Mesh.cdb, these can be renamed to match the Nastran names, simply for consistency in the current documentation). These two materials originally defined properties for the surfaces and for the foam respectively. The foam elements do not appear in Laminate Tools, so the mat1.2 material is redundant. Laminate materials for the surfaces will be modelled by Laminate Tools in the remainder of this tutorial, so the mat1.1 material will also be redundant by the end of this exercise. We can delete both these materials if we wish, but it is best to keep them for consistency of internal identifiers when transferring data between applications. Although some information is lost in the above import process (such as splits, offsets and element sets that we will discuss shortly) and some manual corrections may be necessary, it is a very powerful method of Laminate Tools Tutorial 12/62 Anaglyph Ltd

13 retrieving previously defined plies. The two plies that we have defined will be refined a little later in our exercise. At this point, it is convenient to note that the elements in the new mesh are strictly not properly "aligned". The shaded and custom view modes reveal through subtly different colour shades that the element normals are reversed at certain parts of the mesh surface, as shown opposite. The custom view mode even has an option to display Element Normal Boundaries (as well as the Element Normals themselves, of course). Normally, FE meshes are prepared so that element normals for a surface are aligned. However, we will deliberately leave these normals as they are now, to demonstrate throughout the tutorial that Laminate Tools correctly interprets layer and stress information, whatever the orientation of an element normal. Laminate Tools Tutorial 13/62 Anaglyph Ltd

14 Sets definition Next, we need to create some Element Sets (i.e. groups of elements) to help us with the subsequent ply definitions. BottomSkin element set Select the Bottom Skin Start by viewing the model from the Bottom and ensuring that the entire component is visible. Select the menu Edit / Create Element Set..., or rightclick on and select Create Element Set... In the Element Set Properties window enter the Name as BottomSkin (note: no spaces allowed!). Click and select by Rectangle + (all other options unchanged, such as Visible Elements only ticked, mode Replace, etc.). Click with the left mouse button in the Model window, close to the corner where the tapered bottom section begins at the top right and drag to the left and down to include the entire bottom section, and release. Elements are picked even if they are partially inside the pick shape. The bottom skin should now be selected and highlighted in pink, as shown in the graphic. If you make a mistake and wish to start again, you can select Clear element ID's or Undo element ID's from the menu. Verify and correct Some clean-up might be needed: Click on the toolbar to display the elements filled and make sure that there are no holes left (elements not selected). Rotate the model around the z axis in order to view the background surfaces, starting with the right side: the background surfaces here are clear, so no undesired elements have been picked behind the bottom skin. Rotate again to view the surfaces on the left side. Here, as shown opposite, some elements have been picked unexpectedly because their edges were just visible inside our pick rectangle. We need to remove these elements from this set. Laminate Tools Tutorial 14/62 Anaglyph Ltd

15 Remove undesired elements Elements can be removed in a number of ways: In the Element Set Properties window use to select mode: Remove, and then by Polygon +. Form a polygon that contains all the undesired elements by left-clicking once for each polygon vertex, then leftclicking twice for the last vertex. Alternatively, use to select mode: Remove, then tick Continuous picking, then select by Rectangle +, and proceed to left-click once on each element that needs to be removed. Rotating and zooming the model is possible during this procedure. When you have finished picking, click away from the model. Other methods include the direct modification of element ID's, through Edit Element ID's..., if the logical numbering of the elements makes this a viable option. Some elements might appear to have been picked, when they are not. They are elements from a background surface, but because the graphics must make some approximations when displaying selections, the pink elements appear in the foreground. This usually happens when 2 surfaces come together at a very sharp corner and we view from considerable distance. As we zoom into that area, we see that the elements are not in fact selected. Laminate Tools Tutorial 15/62 Anaglyph Ltd

16 In addition, we can use the General Preferences window's Troubleshooting section to switch off any approximations for graphics: decrease the default 1 to 0 to bring coincident surfaces and lines exactly together, or reset to 1 to improve most visual results and allow the software to display the correct shade when two entities coincide. Finalise the set definition Finally, tick the box Hide the elements in this set and click on. The Data window tree now shows: The X denotes that the elements in this set are hidden. Our first element set has now been defined and all its elements have been hidden. If they are still shown in green this is because the BottomSkin set is currently selected in the Data tree. Click on another tree node or on the background of the Data window to remove the green highlight. Hidden elements are of course invisible and cannot be picked. This will make our next operations easier. If an element is included in more than one set and at least one of these sets is hidden, then this element will be hidden, and because the hidden attribute of element sets is saved in the.layup file format any hidden elements will be invisible on opening a file. The visibility flag for single or multiple sets can easily be modified using the popup menu shown when we right-click on element set nodes selected in the tree. Before we continue, let us save our work with File/Save As..., using Step2.Layup for filename. Channel element sets Start by viewing the model from the Top and ensuring that the entire component is visible. If the BottomSkin set is visible again, hide it by right-clicking on its name, and selecting Hide in the popup menu. If the Element Set Properties window is not visible, right click on Element Set... and select Create Laminate Tools Tutorial 16/62 Anaglyph Ltd

17 Enter the set Name as ChannelP. "P" stands for "positive", this will be the channel in the positive-z half of our component. We could use "+" instead of "P", but "+" is invalid in a filename (operating system limitation), and might give us problems if we wish to use this name as part of a filename for export purposes. The general rule is to avoid using characters in names that are invalid in filenames. Click and ensure mode: Replace, then untick the Visible Elements only option so that any element inside our pick shape will be selected whether in the foreground or not, then select by Rectangle +. Click with the left mouse button in the Model window, near a corner where the channel on the positive z side begins, drag to create a rectangle completely enclosing the channel with plenty of margin around it, and release. The channel, together with many elements from the cylindrical surface, will now be selected and drawn in pink. We need to remove those elements that are not part of the channel. Click and switch to mode: Remove, then select by PLY(s)... A window listing our two plies comes up, select one of them and click OK. This will remove the extra elements on one side of the channel. Now by Element Type(s) and select 3-noded triangles in the window that comes up. This will remove the extra elements on the other side of the channel, as well as those on the cylindrical surface. By now, we have removed all elements on the cylindrical surface, but the last action also removed 2 triangular elements on the channel. These can be identified only if the toolbar button is depressed. Switch to Visible Elements only and mode: Add and use by Rectangle...+ to click on each element in turn, to add them back to the set (hold down Ctrl while selecting the first element, for continuous picking). Laminate Tools Tutorial 17/62 Anaglyph Ltd

18 Now we have selected all the elements on one channel. Make sure that the Hide box is ticked and click. [Tip: an alternative and possibly quicker way to achieve the same result would be to click the Rear view toolbar button, define a clipping plane to hide half of our component (View/Plot Options Window, Clipping tab) and to pick elements (visible and invisible) using a carefully defined polygon enclosing the channel but excluding the cylindrical surface. Omitting the clipping plane would result in both channels being selected, in which case one would need to be removed with a simple second picking operation.] Using a similar procedure, we can build the equivalent ChannelN element set. Holes element set We will now create a set to hide the elements in the two holes. View the model from the Top, in a mode that displays the element edges. Use the View corners toolbar button to click and drag the mouse to define a bounding rectangle around the circular hole in the negative-z half of the component. In the Element Sets Properties window enter Holes for set Name. Click and switch to mode: Replace, then by Ellipse. Click the left mouse button at the centre of the hole, hold and drag outwards to form a circle just inside the hole boundary, and release. Switch to mode: Add, zoom out, and in again, to view the elliptical hole in the positive-z half of the component. As before, by Ellipse and draw an ellipse just inside the hole. If you make a mistake, use Undo element ID's from the menu and try again. Laminate Tools Tutorial 18/62 Anaglyph Ltd

19 Once finished, make sure that the Hide box is ticked and click. We can now save our work again with File/Save As..., using Step3.Layup for filename. Other element sets Using similar techniques, more element sets can be defined. There is no need to do this here in detail, so you can simply open Step4.Layup which includes all the sets we require. Laminate Tools Tutorial 19/62 Anaglyph Ltd

20 Materials definition We already have material Fabric defined, as well as mat1.1 and mat1.2 that have come from the Nastran/ Ansys input deck. We need to define one more material: Right click on, select Create Material... The Material Properties window appears. On the left, enter: Name: UD_prepreg Type: Draped (Slide) Nominal Thickness: Maximum Strain: 20 Note: the Draped (Slide) type of material simulates unidirectional fabric, in which the fibre bundles slide relative to each other as the fabric deforms over a curved surface. Set the anisotropy type to 2d orthotropic. Double-click on the value for Elastic Modulus 11 and enter , then TAB (not ENTER) to move to the value for Elastic Modulus 22, and enter All units are in model units. Geometry has been defined in mm, and loads will be defined in N, so moduli, stresses, etc. are given in N/mm 2, or MPa. Use TAB again for the next value, and so on, to have: Poisson Ratio 12: 0.3 Shear Modulus 12: 5000 Shear Modulus 23: 3500 Shear Modulus 31: (skip with TABs)... Tension Stress Limit 11: 2150 Tension Stress Limit 22: 55 Compression Stress Limit 11: 500 Compression Stress Limit 22: 140 Shear Stress Limit 12: 35 Shear Stress Limit 23: 24 Shear Stress Limit 13: 29 Interaction Term Coefficient: -0.5 After specifying the Interaction Term Coefficient, use ENTER to terminate user input. NOTE: the Interaction Term Coefficient is the factor multiplying the square root of F11 F22 in the energybased failure criteria such as Tsai-Wu. The properties not shown above default to zero. The Property Set Name and Property Set ID (used in FEA) will be automatically defined once the file is saved and re-opened. Click on. Laminate Tools Tutorial 20/62 Anaglyph Ltd

21 We can now also define the mechanical properties for the Fabric material. Double-click on its name in the data tree, set the anisotropy type to 2d orthotropic and enter: Elastic Modulus 11: Elastic Modulus 22: Poisson Ratio 12: 0.3 Shear Modulus 12: Shear Modulus 23: Shear Modulus 31: Tension Stress Limit 11: 1600 Tension Stress Limit 22: 1500 Compression Stress Limit 11: 500 Compression Stress Limit 22: 400 Shear Stress Limit 12: 90 Shear Stress Limit 23: 70 Shear Stress Limit 13: 80 Interaction Term Coefficient: -0.5 The properties not shown above default to zero. Click on. We can save our work again with File/Save As..., using Step5.Layup for filename. Laminate Tools Tutorial 21/62 Anaglyph Ltd

22 Detailed Ply definition In this section we will be examining the various techniques available for ply definition (draping). View the model from the Isometric 2 direction and use the Custom Settings view mode with white background and 70% transparency, for best visual results. In some of the model graphics shown further below, custom colours fave been used for clarity (defined through the General Preferences window), so they may look different to what you might see on your screen. Create a ply Pick the surface Select the menu Edit / Create Ply..., or right-click on and select Create Ply... In the Basic tab, enter: Name: Full_Flat_00 Type: Draped (Scissor) Material: Fabric Laminate Tools Tutorial 22/62 Anaglyph Ltd

23 Click by SET(s) Select OuterFlap to TopSkin (5 sets) and click OK. We can see that the curved surface without the holes has been selected. Define the fibre direction View the model from the Top. On the Ply Properties window click on the button, and move the mouse pointer (cross) near the actual axes origin (denoted by a small red cross). Left-click with the mouse and hold down, then drag along the X direction for a short distance, then release. View the model again from the Isometric 2 direction. We see that the last operation has defined two vectors (as seen previously on page 11): one that defines the direction from which the ply fabric is brought onto the surface (Application Direction, usually normal to the surface at the Start Point), and one that defines a Reference Direction, a reference that will be used for the fibre (warp) orientation at the point of application (Start Point). If you fail to complete this step properly, start again Laminate Tools Tutorial 23/62 Anaglyph Ltd

24 by selecting Clear Vectors first (because the pick operation always re-uses the application direction - as well as the reference direction if there is no dragging - so that an application direction can be defined on a surface and then just moved elsewhere). The vectors are shown graphically, but also numerically in the Ply Properties window. As the graphical picking mechanism is only approximate, in the interest of symmetry it is best to make small corrections to the numerical values that define the two vectors. Enter the following: Start Point: [0 0 0] (origin) Application Direction: <0-1 0> (along -Y) Reference Direction: <1 0 0> (along X) This manual correction will ensure symmetry. To view the results of our editing, we select Refresh Graphics. Finally, we leave the Reference Angle (fibre warp orientation) at 0 degrees relative to the Reference Direction and click to perform the draping with default parameters. The ply has been created, it has been added to the data tree and its properties are shown in the Info window Summary as well as in the Ply Properties window for further adjustments if necessary. Aspects of the ply We will now explore the results for the new ply. First, ensure that the ply name (Full_Flat_00) is selected in the data tree. Then activate the Model window by clicking on it (to enable the graphics toolbars) and unselect all the ply graphics options in the Ply toolbar:. Laminate Tools Tutorial 24/62 Anaglyph Ltd

25 Select (Ply: show Elements) to view the coverage, i.e. which parts of the model are covered by this ply. The coverage is shown here filled and shaded, an option defined in File / General Preferences. Select vectors. (Ply: show Direction) to view the Select (Ply: show Fiber Directions) to view the fibre direction on each element. Select (Ply: show Boundary) to view the outer boundaries, split lines and holes. Laminate Tools Tutorial 25/62 Anaglyph Ltd

26 Select (Ply: show Outline) to view the outline (consult documentation for details). Select (Ply: show Draped Pattern) to view the calculated orientations of the warp and weft fibres. Blue, yellow and red colours are used to show the degree of shearing. [Note: the holes are not omitted in the draped pattern because the draping process needs to cover them with fibres before they are cut out for the flat pattern generation. Hence, a requirement for draping around a hole is the continuation of the element mesh within the hole. Alternatively, the boundary of the hole can be joined to the outer ply boundary using a split. Consult the documentation for further information.] Select (Ply: show Flat Pattern) to view the flat pattern that must be cut for manufacturing. Rotate the ply by 45 While the Ply Properties window is still visible, change the Name to Full_Flat_45, and the Reference Angle to 45. Then click on to create a similar ply but with the fabric orientated at 45 to the first one. The new ply is added to the data tree and the graphics window displays the new draping results. Repeat the above procedure for ply Full_Flat_-45, and a Reference Angle of -45. This is necessary for symmetry, as the mechanical properties of Fabric are different along the 11 (0 warp) and 22 (90 weft) directions. We now have a total of 5 plies defined. We can save our work again with File/Save As..., using Step6.Layup for filename. Laminate Tools Tutorial 26/62 Anaglyph Ltd

27 Create ply over channels Next we need to define plies that will cover the entire surface as viewed from the top, going over the two channels. This will demonstrate how to best drape a surface of double curvature. Select the menu Edit / Create Ply... to display the Ply Properties window with default values. In the Basic tab, enter: Name: Full_Over_00 Type: Draped (Scissor) Material: Fabric Click by SET(s) Select ChannelN to OuterStripP, but without Holes, (9 sets) and click OK. We can see that the surface we want has been selected. For the vectors, enter the following as we did before: Start Point: [0 0 0] (origin) Application Direction: <0-1 0> (along -Y) Reference Direction: <1 0 0> (along X) To view the modified vectors, we select Refresh Graphics. Finally, we leave the Reference Angle (fibre warp orientation) at 0 degrees relative to the Reference Direction and click to perform the draping with default parameters. We observe that some parts of the draped pattern are drawn in yellow, and we even have red used in small areas. Yellow denotes that the calculated shear strains approach the Maximum Shear Strain Angle allowed, as defined in the Material tab of the Ply Properties window. This value usually matches the one given when defining the material itself (page 20) and is known as the "locking angle", beyond which the fabric fails to shear in-plane and deforms (or creases) out-ofplane. Experience or experiment can help quantify this material parameter. Laminate Tools Tutorial 27/62 Anaglyph Ltd

28 A numerical summary of the maximum shearing angles is given in the Info window Summary, where we can see that we have exceeded the maximum allowed shear by about 6%: min.rel.strain = % (actual figures may differ slightly) We now have to find a way to decrease the maximum so that we can successfully drape over the desired surface. First, we will switch to the Geometry tab, accept the default Energy Extension Type, but change the Step Length to 25, Explicit. This means that draping calculations will proceed with a step length of exactly 25 model units (i.e. mm), as opposed to the default 1 internally-calculated relative unit used previously (1, Implicit). Click on and note that the draped pattern is now shown more dense, as a result of the step length change. The yellow and red zones are now clearer, and the Summary window shows that the maximum shear strain is exceeded by more than 10% (calculated more accurately now). The usual technique for improving draping results is to move the initial point of application, or Start Point in the Basic tab. To do this we need to view the model from the Top, reset the vectors with Clear Vectors and the new vectors near the centre of the component as shown opposite, thus smoothing-out any high shear strains over a larger area. Click on and see how the red areas have now disappeared. The Summary window reports that the maximum shear is only about 60% of the maximum allowed, so we have done well to improve the draping. To finalise the ply, it is best to manually ensure symmetry. Modify the vectors to have zero in their z-component: Start Point: [... 0] Application Direction: <... 0> Reference Direction: <... 0> and click on again. Laminate Tools Tutorial 28/62 Anaglyph Ltd

29 Now change the ply Name to Full_Over_45, change the Reference Angle to 45 and click on. Repeat with Full_Over_-45 and -45 degrees. We now have a total of 8 plies defined. We can save our work again with File/Save As..., using Step7.Layup for filename. Draping tubes Our next step will be to drape fabric around the two tubes. We will see how to handle wrapped surfaces, how to apply splits, and how to use a single seed curve. Right-click on the BottomSkin element set name, select Hide in the popup menu, to enable us to view and pick the base of each tube later on. Select the menu Edit / Create Ply... to display the Ply Properties window with default values. In the Basic tab, enter: Name: TubeCellP_00 Type: Draped (Scissor) Material: Fabric Click by SET(s) Select ChannelP and TubeBaseP, (2 sets) and click OK. The tube on the positive-z side of the component is selected. View the model from the Bottom. Pick the vectors somewhere near the centre of the tube's bottom surface as shown opposite. Ideally, manually set the z-components of the Application and Reference directions to zero, for correct alignment. If we now click on, the draping process will probably enter a loop from which it cannot recover. This is because the selected surface wraps around itself and hence the draped pattern cannot find and ending boundary. You can try this, but you will probably need to terminate the calculation using the Abort toolbar button (may need to click on it several times).if we abort, the draping results will be meaningless. [Tip: because of such potential problems, it is good practice to save our work after each successful ply draping.] Laminate Tools Tutorial 29/62 Anaglyph Ltd

30 To achieve our objective, we must "cut" the covered surface. Use a view mode where the element edges are clearly visible and switch to the Splits tab. Select by Polygon + and form a polygon that only just includes a line of element edges from one end of the tube to the other, as shown opposite. Element edges are picked only if completely inside the pick shape. Ensure that no unintended edges have been picked in the background, by rotating the model. Also note that the split cannot be along a branch, for this technique to succeed. We have opted to select the edges closest to the inner side of the tube base. The selected edges will be displayed in the Edges field, and on the model. The element edges are numbered as.1,.2,.3, etc., prefixed with the element number. Each edge is specified once for each element that borders it, so for the case shown opposite each edge is specified twice. For example, the edge that is common to elements 7657 and 7658 is included below as both and The selected line is not a free edge, where we would have 1 element per edge, nor a branch, where we would have more than 2 elements per edge. We can now click on. The draping is successful this time, and the finite boundaries of the ply are clearly seen to border the specified split. To further improve our results, in the Geometry tab, define the Step Length as 10, Explicit and click on. Rotations and zooming will be needed to properly examine the draping results close to the split (shown opposite in a light green colour). Let us save our work again with File/Save As..., using Step8.Layup for filename. Laminate Tools Tutorial 30/62 Anaglyph Ltd

31 If we open a new Flat Pattern window (Window menu), we observe that the flat pattern border at the split is not a straight line. Since fibres are aligned in the X-direction, the small curvature of the boundary will result in small fibre angles along the cut. This is not only awkward for manufacturing, it is also not the intended result for reasons of stiffness and strength. The best technique to force a ply boundary to follow a particular curve is to use a seed curve, a technique that has numerous practical applications. We will use this technique shortly, but we note that in this particular case, the geometry is suitable for the problem to be corrected simply by switching the Extension Type from Energy to Geodesic, in the Geometry tab. Try it, click on and observe the effect. For the purposes of our tutorial, switch back to Energy to demonstrate the use of a seed curve in achieving the same result. Then go to the Seed Curve tab, set Axis Type to Single and Direction to Warp. This means that warp-direction fibres will be forced to follow the curve defined by the element edges in the Edges field. Ideally, we would like the seed curve to coincide with the ply edge. However, in this particular case the edge is also defined as a split and, although it is possible to have splits and seed curves coincide, it will be simpler for this tutorial to choose another line. Therefore, we will choose the series of element edges immediately next to the ply edge, as shown opposite (orange line). If we now click on, we get an error that the ply modification failed, and the Feedback window informs us that "The start point must be within units of the selected single manual axis...". Laminate Tools Tutorial 31/62 Anaglyph Ltd

32 This means that we have to move our ply's Start Point to be very close to the seed curve we have chosen. This is a requirement for seed curves! In the Basic tab, use (do not clear the vectors) to click as close as possible to the seed curve, without dragging, so that we keep our reference direction. You will have to hide the BottomSkin element set if it is visible, and you will have to zoom in a fair amount in order to get close enough to the seed curve, while preferably keeping the start point on the same side of it as previously. For completeness, ensure that the Application and Reference vectors have zero z-components, that the Reference Angle is 0, and click on to finalise a successful draping. We can then create plies at +/-45 degrees in the usual manner, for which a seed curve will not be necessary. We now have a total of 11 plies. Let us save our work again with File/Save As..., using Step9.Layup for filename. Refine the original plies The two plies that were imported onto this mesh need to be refined. The "draping order" option will be demonstrated. First, we need to make the elements in the BottomSkin set visible, if they are hidden: double-click on the BottomSkin name in the data tree, untick the Hide box and click on. Then close the element set properties window. Laminate Tools Tutorial 32/62 Anaglyph Ltd

33 Double-click on the Ply_001 name in the data tree and view the Basic tab of the Ply Properties window. Change the name to Full_Under_00. Enforce symmetry by specifying z=0 for the Start Point, Application Direction and Reference Direction. Next, we will demonstrate the use of the Drape Order tab. This is used to instruct the draping simulation to cover specific parts of the structure in controlled succession. The idea is to ensure maximum coverage over surfaces that drape without much - or any at all - shearing, before proceeding with surfaces that will shear the fabric. This method normally reflects real-life draping techniques. Although our component is simple and does not require the use of any specific draping order for improved results, we will demonstrate its use. The first surface to be covered is defined in the Basic tab: click on by SET(s)... and select BottomSkin. Switch to the Drape Order tab, highlight the second row in the table, click on by SET(s)... and select OuterFlapN to OuterStripP (4 sets). Finally, click on. Repeat the above steps for Ply_002 (and change its name to Full_Under_45), and create one more at -45 (Full_Under_-45). Save the plies with File/Save As..., using Step10.Layup for filename. Review all Plies We need to create a few more plies: some to cover the tube on the negative-z side of the component just as we did for the positive-z side, and some unidirectional plies over the channel sections, as stiffeners. We will also create two dummy plies to cover the two holes, otherwise the elements in the holes will have no material assigned to them and the static analysis will fail. The material we will use for the holes is mat1.2 (with its thickness set to a dummy value), which was originally defined for the sandwich foam and which has very low stiffness. Alternatively, if we do not wish to define dummy plies for the holes, we would have to manually define dummy properties in our FEA pre-processor, or even delete the elements in the holes prior to analysis. The latter method would make more sense since no stress results would be generated for the elements in the holes, but would require tricky changes that we want to avoid in this tutorial. You may now open file Step11.Layup, where all these plies have already been defined for your convenience, and examine them. Try to recreate them yourself if you wish, as an additional exercise. Note in particular the "hat" plies that use unidirectional material, rather than woven fabric. A total of 21 plies exist now, and we are ready to proceed with the next step, which is to stack our plies to create a Layup. Laminate Tools Tutorial 33/62 Anaglyph Ltd

34 Create a Layup Select the menu item Edit / Create Layup... and the Layup Properties window will appear. This window offers a number of functions to quickly define a stacking sequence for the plies making up the structure. Each of the plies we have defined can be used in multiple instances here. Each instance - called a layup ply or layer - will represent an individual piece of material that will have to be cut, identified and used when necessary. The stacking sequence defines both the physical make-up of the composite layup and the steps necessary for its manufacture. For more information, consult the documentation which can be accessed by hitting F1 on the keyboard. First, enter a Name for the new layup: Component. Next, click on the button: to display the Layup Builder window which is used to quickly select and stack our layup plies. Double-click in turn on plies: TubeCellP_00 TubeCellP_45 TubeCellP_-45 TubeCellP_00 TubeCellN_00 TubeCellN_45 TubeCellN_-45 TubeCellN_00 In case of a mistake, use the Undo button and repeat. Each ply's new instance is appended to the layup. We have now defined the manufacturing sequence and the fibre orientation for the two tubes on their own. More layup plies will soon be wrapped around the tubes to fully integrate them in the component. Note that we cannot "freely" add layers or move them up and down. We are limited by the way the plies are defined and by whether a particular sequence is physically possible. Laminate Tools allows any logical operation at this stage, but once the layup is defined it will be checked for consistency and warning messages may appear in the Feedback window. For example, it makes sense to build the tubes outwards, adding material on the outside each time, and then to wrap other layers over them. You may experiment later with stacking configurations that do not make physical sense, and observe the results. Continue with the layup definition by further appending plies: Full_Flat_45 Full_Flat_-45 Full_Flat_00 Full_Flat_-45 Full_Flat_45 Full_Under_45 Full_Under_-45 Full_Under_45 Full_Under_-45 Full_Under_45 Full_Under_-45 Full_Under_-45 Full_Under_45 Full_Under_-45 Full_Under_45 Full_Under_-45 Full_Under_45 Laminate Tools Tutorial 34/62 Anaglyph Ltd

35 Full_Under_00 TubeHatP_00 TubeHatP_90 TubeHatN_00 TubeHatN_90 Full_Over_-45 Full_Over_45 Full_Over_00 HoleP HoleN This will create a layup with 35 layers. Note the Global ID column: this uniquely identifies each layer (or layup ply) and can be used for manufacturing purposes, or for sorting FEA results by "global ply" during post-processing as we will see later on. Click on, then OK to confirm, the layup is created and Laminate Tools briefly pauses to build the necessary information. Save the plies and layup with File/Save As..., using Step12.Layup for filename. The layup graphics show by default the thickness distribution resulting from the newly defined layup. Hide the Holes element set for better results. We can immediately confirm the symmetry of the ply usage. You may wish to explore the graphics available through the other Layup toolbar buttons: - surface angles, wireframe surface, solid surface, single element layup and cross-section of layup. The Layer Control tab of the Plot Options window can be used to exaggerate the drawn layer thickness for clarity. Laminate Tools Tutorial 35/62 Anaglyph Ltd

36 In addition, each layup ply (or multiple layup plies) can be selected in the data tree to display its coverage, its position exploded or in-place, etc. Explore the functionality of the relevant toolbar buttons:. Again, the Layer Control tab of the Plot Options window can be used to control the attributes drawn. The data tree displays the relation between plies and layup plies in three ways: via red tick marks, by using the ply name in the layup ply name, and by adding layup plies below the ply that they originate from. Finally, now that the layup is defined and therefore the material usage is finalised, clicking on a material name in the data tree displays its usage on the graphical model. The usage for the UD_prepreg material is shown opposite (select the material in the tree to display this). Laminate Tools Tutorial 36/62 Anaglyph Ltd

37 Offset definition As layers are added to the layup, the resulting stacking sequence at any particular point is assumed to be equally distributed either side of the element mesh surface. This is not always what is intended, because the element mesh is usually modelled to coincide with one side of the expected structural thickness, i.e. with either the top or the bottom surface of the local laminated material. In order to match this behaviour, we must define Offsets: these are used to exactly locate the local layup with respect to the local mesh surface. Let us begin by defining an offset for the BottomSkin element set, which includes the bottom surface of the sandwich. Ensure that the BottomSkin element set is visible, then select Edit / Create Offset..., then by SET(s)..., select BottomSkin and OK, view the model from the Bottom and click on to define the Definition Point somewhere near the middle of the bottom skin surface, with the Definition Direction normal at that point by default. We will use and Top for Value and Flag. Note that the default value of "0" is often misinterpreted by some FEA pre-processors (including Femap) to mean "no change from the default setting" (the default setting is for a balanced laminate about the mid-plane and that is not the same as "0 from Top" which is defined in a Nastran PCOMP card with an explicit 0 rather than a blank). That is why we use here, a small enough value to approximate 0. Click on to create the first offset definition. Offsets are not given a name, they are simply numbered sequentially from 1 onwards. By using (essentially zero) and Top, we instruct Laminate Tools to offset the local layup for the selected surface so that the last layer, as seen from the Definition Direction, is adjacent to the element mesh surface. We can visually examine the results of the offset definition by checking the local element layup (toolbar button ) for a single element on the bottom skin surface. Exaggeration of the layer thickness helps with visualisation. Try also fixing the graphics rotation centre on the chosen element (use toolbar button ), to zoom in and rotate the view, to best understand the local layup. Use the button to reset the rotation centre. Or we can review the in-place layer graphics for global ID layers 1014 to 1026 (in-place layer graphics take offsets into account). Laminate Tools Tutorial 37/62 Anaglyph Ltd

38 We must define similar offsets for the entire model. This has already been done for you and is available in Step13.Layup, so open this file now and examine the 6 offsets defined. It is recommended to use the Solid Surface layup graphics to view the build-up of the material relative to the original surfaces. This graphical option even shows clearly the ply drop-off effects, such as along the edges of the TubeHat plies. Try also the in-place layer graphics layer (with global ID 1033). for the 33rd The cross-section graphic now shows the layer locations as intended. Laminate Tools Tutorial 38/62 Anaglyph Ltd

39 Laminate generation At this point we have built our entire component out of composite materials. The layup we defined completely covers all surfaces and the global ply information is stored for later reference or modification. We may now, if we wish, proceed with manufacturing. This involves extracting from the model the flat patterns that need to be catalogued, nested, cut and laid-up. However, FEA is usually necessary to ensure structural integrity, so we will first go through this step before proceeding with the manufacturing procedures later on. For FEA, we need to define laminate properties for each finite element. Our global ply information will be used for this, and all we have to do is select the menu item Edit / Create Laminates from Layup... A window appears, where we specify a number of options for translating ply results to local element laminates. If we are working with Nastran, we can set the Laminate Orientation data to be generated based on one of 3 options: Default Nastran, First Ply, or Existing. The Default Nastran option uses the first element edge as local reference and produces many laminates, even when the global fibre orientations are identical. The First Ply option uses the first laminate layer as reference and hence all laminates start with a 0 layer. This option groups similar (adjacent) laminates better, so we will use this instead of the default. If we are working with Ansys, we can set the Laminate Orientation data to be generated based on one of 2 options: Default Ansys, or Existing. The Default Ansys option uses the local element x-axis as local reference, and this will be our choice here. The option Existing keeps the laminate orientation method unchanged and can be used, for example, in cases where the material axis orientation has previously been defined in the FEA pre-processor relative to a global axis system. In a complex geometry with significant ply shearing, it is likely that each element can be assigned a unique laminate property. However, a large number of laminate properties can slow down the FEA solver, hence the Tolerance options allow for some grouping of similar properties in order to reduce their number. We will leave these at their default values. The Laminate Prefix is simply a name for the laminates to be generated. For convenience, use pcomp for Nastran output. The First Laminate id will be set to 3 because there is already a dummy shell property defined in our original FE model with an id of 1, and the foam property with an id of 2. In general, this number is used to avoid clashes with other property (Nastran) or section / real constant (Ansys) identifiers that are not present in Laminate Tools. Laminates may be created as many times as necessary, and each time the new set replaces the old one. The laminate information is not saved in the Layup file format. However, the parameter values used in the laminate creation window are recovered every time laminates are created, to ensure consistency. If you wish to learn more about these parameters, hit F1 and the online help will display the relevant topic. Laminate Tools Tutorial 39/62 Anaglyph Ltd

40 If working with Nastran, you may notice that default options result in over 400 laminates. Using the First Ply option we reduce this to just 47, shown as pcomp.3 to pcomp.49 in the data tree. Select a laminate and use the Laminates and Laminate Layers toolbar buttons: to explore the graphics, as well as the Summary window information. The graphics are similar to what we have already seen for the Layup. In particular, select all the laminates together (Shift or Ctrl + click method, or via context menu, or via ) and observe that the results are almost identical to those seen earlier for the Layup. This is because we are simply looking at the "same" information, but expressed in two different ways. We are now ready to save the laminate properties for use in our FEA analysis. Laminate Tools Tutorial 40/62 Anaglyph Ltd

41 Nastran users may select the menu item File / Export > Model to Nastran data... and save as Step13.nas. The exported file contains: nodal information (GRID), shell element definitions (CTRIA* and CQUAD*), material properties (MAT*), and laminate properties, including offsets (PCOMP). The laminate property information must somehow be "blended" with the original FE model (in the file Mesh.nas), which - in this case - contains everything but laminates, including the sandwich core solid elements, boundary conditions and loadings. The easiest way to achieve this is to check the box Include any unprocessed lines in the Export to Nastran window above. This option is available ONLY if the Laminate Tools file was originally created from a Nastran input deck, and allows for the reconstruction of this deck by carrying through any Nastran commands that are not processed by Laminate Tools. However, the supplied tutorial Layup files have been created so as not to include this information for space saving reasons, so this option box is not available if you have used any of the supplied Layup files. However, it is often the case that changes to the original Nastran deck have become necessary, such as changing loadcase data. Then, the simplest way to "blend" the revised Nastran deck (such as Mesh.nas) with the generated laminate data in Step13.nas is with a text copy and paste operation using a text editor such as the Windows Notepad (although a more advanced editor is recommended). Note that (a) copying the PCOMP lines alone is not adequate: we need to (b) copy also the shell element definitions (which reference the PCOMPs) and (c) the material properties (which are referenced in the PCOMPs). And (d) we have to delete the original lines that we are replacing. Fortunately, Nastran cards are nicely grouped together, so this step is very easy to complete. Once this is done for the tutorial data, save the "blended" file as Step14.nas. Alternatively, we can use our Nastran pre-processor, such as Femap, to "import" Step13.nas into our original model database, available here for completeness in Component.MOD. This operation will generate many warnings because we will be overwriting existing entities, but will also work and will give us more room for modifications etc. Ansys users may select the menu item File / Export > Laminate Updates to Ansys... and save as Step13.inp. The exported file contains: material properties (MPDATA and real constants), laminate properties, including offsets (SECBLOCK and real constants), and shell element section assignments (EMODIF). This file must be brought into Ansys to update the element properties: in the Ansys environment, open the model database (available here for completeness in Component.db, from where Mesh.cdb was exported) and type /INPUT,Step13,inp in the command window. The result may optionally be re-exported from Ansys as Step14.cdb (command CDWRITE,db,Step14,cdb). The Ansys database itself must NOT be overwritten. Save the current state of the Laminate Tools model in Step14.Layup (but note that the laminates are not saved in the.layup format, so there is no real difference from Step13.Layup!). Laminate Tools Tutorial 41/62 Anaglyph Ltd

42 Static Analysis Nastran users: The Step14.nas file can be passed directly into a Nastran solver. In order to use Laminate Tools as post-processor, we must save the results in the.op2 or.f06 format. The types of results that Laminate Tools can read from such files are: Shell Forces Layer Stresses, at element centroid Layer Failure Indices, at element centroid Layer Reserve Factors, at element centroid. Ensure that the output options include at least Layer Stresses, calculated at element centroids. Laminate Tools can then calculate failure indices etc. Alternatively, if only the Shell Forces are saved, Laminate Tools can calculate all other results (layer stresses, failure indices, etc.). This can save considerable disk space during solution, but can also allow for interactive recalculations, as we will see later on. IMPORTANT: for this feature to work correctly, the Shell Forces must be saved in the element local coordinate system (parameter ELEMRSLTCORD=ELEMENT for some Nastran implementations). The results shown further below have been generated with NX Nastran version 9.3. There are two sets of results available in the tutorial distribution: Step14-stresses.op2 (contains shell forces and layer stresses), and Step14-forces.op2 (contains shell forces only). Ansys users: Having read file Step13.inp into the Component database (see above), users may Solve applying the loadcase data available in LS files 1, 2 and 3. When Laminate Tools is used as a post-processor, results are accessed via the.rst format file. The tutorial distribution includes Step14.rst, which contains model data and element shell forces. These results have been generated with Ansys version 11. Laminate Tools Tutorial 42/62 Anaglyph Ltd

43 Post-processing In order to start afresh, close any open file, open Step14.Layup and recreate the laminates using the same options as before (important!). Let us also hide the Holes element set, for convenience. Then, select File / Import > FEA Results..., or click on the toolbar button. Nastran users: Select the file Step14-stresses.op2 and Open it. [Alternatively, we can first open Step14.nas and then import Step14-stresses.op2. In this case, we will have all the model and laminate information, but not the global plies and layup which are very useful for specialised post-processing.] Ansys users: Select the file Step14.rst and Open it. [Alternatively, we can first open Step14.cdb and then import Step14.rst. In this case, we will have all the model and laminate information, but not the global plies and layup which are very useful for specialised post-processing.] In the remainder of this document, graphics, names and numerical values are based on the Nastran results. Post-processing the Ansys results is very similar, although the native Ansys layer stresses and failure calculations are not available directly within Laminate Tools. Instead, these are calculated interactively as explained from page 52 onwards. The documentation starting immediately below is almost fully relevant to Ansys users, except for the beginning of section Failure Calculations, because Ansys users do not have to explicitly calculate failure indices. Also note that, as expected, the results from the two solvers differ slightly due to differing element formulations. Stresses We now have a new Results Toolbar in the Data window, and the node in the tree now contains 3 branches: each branch is a loadcase for the results. Under each loadcase branch, we have one branch for every subcase present (only one here). Under each subcase branch, we have one branch per result type. Under each result type, we have a further level specifying an attribute. Under each attribute, a final level gives access to results layer by layer. (consult the documentation for full explanation of what appears under the Results node). Laminate Tools Tutorial 43/62 Anaglyph Ltd

44 Left-click on the Layer 1 node under Stress Tensor of the third loadcase EDGE FIXED - HOLE PUSH: the Model window shows the Stress11 component (along the warp fibres) for layer 1 of all available laminates, and the Summary window presents a table of Stress11 values by element, sorted in descending order, and truncated to the most positive 25 and most negative 25 occurrences. Let us first remove all results for the elements in the holes: click on the button, and in the window that appears click on. Then select all sets except Holes and click OK twice. Finally, tick the box to exclude the Holes from any post-processing (element invisibility is not the same as exclusion from post-processing!). Now click on Layer 16. Notice how results are not available everywhere, because we do not have 16 or more layers everywhere. Laminate Tools Tutorial 44/62 Anaglyph Ltd

45 In the Results Toolbar, set Display to on worst Layer, to show exactly where this 16th layer is for each laminate. Note how the single-layer results can be misleading regarding physical fibre continuity around areas of ply drop-off and element normal reversal. This is because the single (16th) layer for adjacent elements is not necessarily the same physical layer. We will resolve this problem soon. Reset the Results Toolbar: Display to on Element and click on the third loadcase node EDGE FIXED - HOLE PUSH. The results now show the worst Stress11 value for each element (from all its layers, chosen by magnitude when we have both tensile and compressive data), for this loadcase. Select all 3 loadcase nodes, and we now show the worst Stress11 value for each element from all 3 loadcases! The Summary window identifies which loadcase and layer are critical for each one of the listed elements. In brief, the TUBE PULL (second loadcase) is critical for tensile stresses and BOTTOM PRESSure (first loadcase) is critical for compressive stresses, but for the same laminate layer (5) in the same part of the model! Notice how the yellow- and cyancoloured elements are near to each other (the locations of the highest tensile and highest compressive stresses respectively) on top of the negative-z side tube, close to the supported end. For the record, the component is fully fixed along its curved edge that runs roughly along the z-direction. The BOTTOM PRESSure loadcase (1st) is a nonuniform pressure on the bottom skin of the sandwich core, the TUBE PULL loadcase (2nd) is a distributed force pulling the tubes along the x-direction, and the HOLE PUSH loadcase (3rd) is a distributed force along the hole boundaries, approximately in the negative y-direction. A graphic of the deformed shape for the pressure loadcase is shown opposite (graphic generated with Femap). A frequent question is: why do the Laminate Tools graphical results look "chunky" and there is no smooth contouring? This is intentionally so, because results from adjacent elements are not necessarily for Laminate Tools Tutorial 45/62 Anaglyph Ltd

46 the same physical layer or loadcase, so it would be misleading to display a "smooth" transition. Another frequent question is whether the default colour spectrum can be changed. The answer is that users can apply other colours via the Results tab of the Plot Options window, with examples shown opposite. If you want to always use the "traditional" spectrum by default for files that have not been viewed yet, tick the appropriate box in the General Preferences window. The developers of Laminate Tools opted to use the built-in red-white-blue spectrum because of the requirement for "chunky" graphics, and to differentiate from the commonly used traditional spectrum which is normally associated with smooth contouring. Next, use the Process drop-down list in the Results Toolbar to explore the other stress components: tensile only, normal to the fibres, transverse throughthickness stresses, etc. Laminate Tools Tutorial 46/62 Anaglyph Ltd

47 Also explore the Display : worst Elements, all Layers option in the Results Toolbar. The results shown below are for the HOLE PUSH loadcase, Stress11 and StressYZ. Here, we display the worst results for ALL the layers of the 50 worst-loaded elements. This type of results summary helps appreciate the degree to which stresses are well distributed throughout the laminate layers, i.e. whether we are making good use of the material in matching fibre orientations to principal load paths. Furthermore, we can check the results layer-by-layer for an individual element: select Window / New Stress/FI Plots Window, or click on the toolbar button, to display a Plot window. Before proceeding, ensure that all 3 loadcases are selected in the tree and we are processing Stress11, displayed on Element. Normally for this combination, element id is reported as the one with the highest tensile stress, and highlighted in yellow in the graphics. On the Plot window click on the element id button, which is blank, and either enter the id directly, or the yellow element from the graphic window. Click on OK and the warp layer stresses will be shown for the first loadcase. Select the TUBE PULL loadcase that causes the critical stress and examine the results layer by layer, also exploring the other stress components. Moving the mouse pointer over the plot area, a small popup window identifies the underlying layer/interface and displays its results. Laminate Tools Tutorial 47/62 Anaglyph Ltd

48 To show the same results in text, select the graphics window, click on the toolbar button and pick the same element. The Summary window now displays a full report for element 12970, including laminate information and FEA results. This report may be copied to the Windows clipboard, for easy inclusion into documents, or for further processing in spreadsheets. Failure calculations [Ansys users: explicit generation of failure results is not necessary, skip to the next page] The Nastran solution has not produced any Failure Index or Reserve Factor calculations. If it had, those results would be included in the node (under each subcase) and we would be able to postprocess them in exactly the same way as we have just seen with stresses. Laminate Tools is able to generate failure results itself, based on the combination of: FEA layer stresses (as imported from.op2 or.f06), laminate information (as imported from.nas or created from the compatible layup) and material allowables (as imported, or specified during the session). To generate failure results, select the menu item Edit / Create new FI Results..., or click on the toolbar button. In the window that pops up, select all 3 loadcases, the Tsai-Wu and Maximum theories, all types of results to calculate, and Stress as the basis of calculations. Laminate Tools Tutorial 48/62 Anaglyph Ltd

49 Click OK, and observe the new results branches added to the tree. The generated results are added to the tree in addition to any Nastrangenerated ones, and are available for processing as normal. They are differentiated from any Nastran results by an asterisk (*). They cannot be saved when we close a model file and must be regenerated every time we want to post-process them. For our convenience, Laminate Tools offers to automatically do so when re-opening the stress results, provided the relevant option in the General Preferences window is enabled. Repeat the failure calculation, for all loadcases, Maximum theory, all result types, but based on Strain this time. This will add Maximum Strain failure theory branches to the tree. In the data tree toolbar, set Process to Failure Indices* and select each loadcase in turn. Note from the Summary window how Laminate Tools shows the worst value for each element, from all layers and failure theories. The critical component is also shown in each case. Then note that the maximum calculated failure indices for the 3 loadcases are: , and (). This means that the component is not strong enough for 2 out of the 3 design loads, the pressure load being the worst one (of course you may work with Margins of Safety* or with Reserve Factors* instead, if preferred). Select all 3 loadcases together and this time observe the graphics window. By default, Laminate Tools displays 4 levels for failure results: red for "failure", pink for "alert", light pink for "warning", and clear otherwise. In this fashion, users can instantly check whether, and where, further action needs to be taken. Laminate Tools Tutorial 49/62 Anaglyph Ltd

50 The values delimiting the 4 levels are usercontrollable in the Results tab of the Plot Options window. Alternatively, the "traditional" colour spectrum may be applied. As previously, we can examine the failure results for individual elements, layer by layer (will need to click on if the Plot window was open prior to generation of failure results). Notice how the layers where a failure index (from any available theory) has exceeded 1, are shown in red. [Tip: if some material allowables are now modified and the same failure results are simply regenerated, the new failure results will use the modified material allowable data. In this fashion, a number of what-if scenarios may be quickly investigated.] We are now faced with the challenge of making changes to the component's layup to make it able to withstand the 3 design loadcases. Our design goal will be to reduce all failure indices to just below 1. Our first step in deciding what to do is to relate the failure results (and the stresses) to the original layup plies. Examination of the Summary window report for failure indices for all 3 loadcases shows that the worst element is Laminate Tools Tutorial 50/62 Anaglyph Ltd

51 Using the Plot window, we see that for element 12969, laminate layers 2, 3, 7 and 8 are all failing. By moving the mouse cursor over the failing layers, or......by picking element as before to display its laminate properties... we see that these laminate layers correspond to the layup ply global ids 1032, 1031, 1007 and 1006, or to individual instances of plies Full_Over_45, Full_Over_-45, TubeCellN_-45 and TubeCellN_45 respectively. We now need more information on these specific global plies. Global Ply sorting We can project our stress and failure calculations results onto the above global plies, to better understand the nature of the problem: Click on the button, clear all global plies' check boxes (click on ), then check the global ids that interest us, either all 4 or just one of them. The two pictures below show the FI* results from all theories and loadcases for layup plies 1032 and then 1006, individually. In each case, the results come from the same piece of fabric material, so continuity in colour shading is better. Our earlier problems of not being able to relate an element laminate layer to a physical ply, and not being sure of results continuity from one element to the next (when we examined results from Layer 1 or 16 alone) have been overcome. In this fashion we can query the FEA results and failure calculations to best appreciate what is happening to an individual global ply, and what to do in order to improve our design. Laminate Tools Tutorial 51/62 Anaglyph Ltd

52 Interactive calculations Ideally, we would like to be able to see interactively what happens to the stresses and failure calculations, as we make changes to the layup. For example, if we choose to rotate the Full_Over_45 and Full_Over_-45 plies in an attempt to reduce their failure indices, is there a way to instantly estimate the redistributed stresses and hence the failure indices? We will now see how this is possible with Laminate Tools! Let us first select File / Close if a model is still open, then load file Step14.Layup again, and recreate the laminates using the same options as before (important!). Let us also hide the Holes element set if visible, for convenience, and ensure that in File / General Preferences, ONLY the theories Tsai-Wu Stress, Maximum Stress and Maximum Strain are checked for interactive calculations. Then, select File / Import > FEA Results..., or click on the toolbar button. Nastran users: Select the file Step14-forces.op2 and Open it. [Alternatively, we could continue from the previous state and unload the existing FEA results with File / Import > Unload FEA Results, before importing Step14-forces.op2 and resetting the scope to all plies.] Ansys users: Select the file Step14.rst and Open it. Proceed by excluding the Holes element set from post-processing, as before. The imported Nastran results this time include the shell element forces only (in the element local coordinate system), just like the Ansys results. Laminate Tools then uses these forces, together with the laminate information, to calculate layer stresses and strains interactively, i.e. every time we select a node in the Results branch. Furthermore, any available material allowables are used for interactive failure calculations, based on the theories selected by the user in the General Preferences window, which are by default: Tsai- Wu, Maximum Stress and Maximum Strain. The first thing to check is whether the interactively calculated stresses agree with those imported previously from Nastran. Set Process to Stress11 and select all 3 loadcases. The result, shown opposite, agrees with what we saw previously (the calculation is almost instant). [Differences will be noticed for transverse shear stresses between different implementations of Nastran. Laminate Tools uses by default the methods adopted by MSC.Nastran - NX Nastran for transverse shear calculations - see Preferences.] Repeat with Process set to Failure Indices* and confirm that values are same as before. The calculation takes just a little longer this time because 3 failure theories (default setting) must be calculated in addition to the layer stresses (use the Abort button if you wish to interrupt a very long calculation). [We may occasionally see differences compared to previous results, because this interactive calculation takes account of transverse stresses at layer interfaces separately to layers, whereas the noninteractive method seen previously does so in an integrated way.] Laminate Tools Tutorial 52/62 Anaglyph Ltd

53 Again as previously, we can inspect stresses, strains and failure results for individual elements layer-bylayer, in a Plot window (user-defined axis scale shown). Note that failure results for layer interfaces (transverse stress effects) are now calculated and plotted separately to those for layers. For the record, below we compare the results between the two solvers supported: (worst stress along the fibres from all 3 loadcases, Nastran on the left, Ansys on the right) So, since the stresses and failure indices are now calculated interactively, what will happen if we modify the layup? If the changes are small, we can assume that the overall shell forces will not change much, so our interactive layer stress calculations will be approximately valid. In any case, they should give a very good indication of the effects of our changes and hence qualify a modification strategy. Let us first try to rotate the unidirectional plies in the tubes where the fibres run along the component: plies with global ids 1001, 1004, 1005, Double-click on the layup name in the tree (Component), select the global plies 1001 and 1005 (TubeCellP_00 and TubeCellN_00), place the cursor in the edit box above the Angle Offset column, type -10 and press Enter. Repeat for global plies 1004 and 1008 with a value of +10. What is this angle offset? It is merely a small deviation from the angle defined for the ply. Strictly, any such deviation invalidates the draping results and this field must not be used normally, but it is useful for quick (and temporary?) small changes to individual plies in the layup. Click on and confirm. Now we have a new Layup, so we must recreate the Laminates! Do so in exactly the same way as before, and a new set of laminates are now available. Set Process to Failure Indices* and select all 3 loadcases. [Tip: To select the 3 loadcases, we have to select the first one, then Shift+Click on the third one. But clicking on the first one may cause a long calculation for a large model that we do not need. We can Abort this! Laminate Tools Tutorial 53/62 Anaglyph Ltd

54 Alternatively, we can untick the box (which turns off the actions taken when we select something in the tree), complete our selection, tick the box again, and choose Model / Refresh Graphics.] The Summary window shows that the maximum failure index is still at the same position, but for Nastran it has risen from to (for Ansys from to ). Our modification has not helped. If we apply the angle offset in the opposite direction (swap the -10 and +10 ) we find that the failure index still rises. To speed up the interactive processing for very large models, we can restrict the Scope to a smaller number of elements. In our case, we will restrict to element sets ChannelP and ChannelN only. So the modification we have chosen is not good for the failure index. We need more dramatic changes to more than halve the maximum failure index value. We have a number of options: shuffle the layup plies to improve bending properties, replace 45's by 0's, or the opposite, to better match load paths, add more layup plies, change the material with a stronger one, define new plies altogether. Any of the above can be "tried" interactively. But watch out for the effect of Offsets! If we add a layer to a laminate for which an offset has been defined, the (existing) shell bending moments are no longer valid in relation to the shell forces, and the resulting imbalance has a great effect on layer stresses. The best solution is to modify the Offset temporarily so that equal thickness of material is added on either side of the element plane. Let us now try another modification. First, reset the angle offsets we have just modified to zero, and then add the following 3 plies after the layup ply with global id 1033: Full_Over_-45 Full_Over_45 Full_Over_00 Double-click on Offset 5 in the tree, and change its offset value to -0.3, to counteract the effects of the imbalance as a result of adding 3 layers of total thickness 0.6. Repeat for Offset 6. We will not worry about the other offsets, as we are interested mostly in the results for the elements in sets ChannelP and ChannelN, fully covered by offset definitions 5 and 6. Recreate the Laminates as usual, to propagate the effects of the changes in the Layup and Offsets. Select the 3 loadcases for post-processing, and note how the maximum index is now just for Nastran, for Ansys, still at the same position. This change reduced the indices considerably: Laminate Tools Tutorial 54/62 Anaglyph Ltd

55 Following a number of trials to decide how to finalise a design, we will have to repeat the FE analysis to confirm the calculations. But we must remember to reset the Offsets to their proper values before recreating the laminates one last time and exporting to FEA! Laminate Tools Tutorial 55/62 Anaglyph Ltd

56 Final design The final layup that we have designed can be found in file Step15.Layup, with accompanying Nastran FEA files Step15.nas (includes loads etc. from Femap) and Step15-forces.op2, or Ansys files Step15.cdb and Step15.rst. Open file Step15.Layup, hide the Holes element set, and notice how we have added several "short" layers over the top of the component; but also how we "shortened" some layers around the bottom, where stresses are low and we could afford to save some material. It is equally important to note that we have renumbered the global layup ply ids to be fully sequential, by selecting them all in the layup definition table and clicking on. We also had to redefine the offsets, as the "short" plies created areas with new thickness that were incorrectly handled by the previous offsets. Generate the laminates exactly as previously and import the FEA results from Step15-forces.op2., or Step15.rst. Then post-process results as before: Set Process to Failure Indices* and select all 3 loadcases. Examine the processed values, in the Model window, in the Summary window and in a Plot window, and confirm that the design goal has been achieved (Nastran results shown below). Laminate Tools Tutorial 56/62 Anaglyph Ltd

57 As an additional exercise, you can generate failure indices using Nastran or Ansys itself and compare the native FEA results to the Laminate Tools ones. Laminate Tools Tutorial 57/62 Anaglyph Ltd

58 Manufacturing Laminate Tools can export: Plybook data (either in single or in multiple operations) Flat or Draped Ply Patterns (either in single or in multiple operations) Laser Projection data for manual ply placement the Mould Surface The most popular function is the Plybook export, which we will examine below. Open Step15.Layup (if not already open) and select File / Export > Ply Book to HTML/CAD... The window shown below appears, where we select the layup plies that we wish to appear in the plybook. The selection is done either directly or based on material. The plybook will be generated by default in the.html format, which is readily readable by any web browser, on any standard computer running Windows, MacOS, Linux, etc., so maximum portability is guaranteed. The.HTML plybook may even be read directly into Word, Excel, etc. It is a great way to document and communicate the layup information. The plybook that we will produce will contain a table with one row per layup ply, for which information will be listed as specified in the Table Columns list box. The plybook will also contain images of the exported layup plies, with graphics options as specified via the Ply Graphics list box, but also via the currently open Model windows (for view mode and angle of view). In addition, we may choose to export CAD files (IGES and/or DXF) for the Flat and Draped Patterns for each layup ply. The flat pattern files can be passed to a nesting application, or directly to a cutting machine for production. We can even apply an extension boundary around the flat DXF outline, to allow for in-place trimming. Finally, we have the opportunity to generate Laser Projection data to be used with suitable hardware during hand layup. Laminate Tools Tutorial 58/62 Anaglyph Ltd

59 We click OK when our selection is complete, and after a short pause the web browser is automatically launched with the plybook displayed in it: Laminate Tools Tutorial 59/62 Anaglyph Ltd

60 Customisation of the plybook is optionally available for output directly to Word, with bespoke page layout, specific information fields, company logos, etc. Sample pages are shown opposite, contact your supplier for further information. Laminate Tools Tutorial 60/62 Anaglyph Ltd

61 Another feature useful for Manufacturing is the Flat Pattern Window (Window menu). This utility window allows users to drape arbitrary pre-existing flat patterns onto parts of the model for which draping has already been applied successfully. Full details can be found in the documentation but, in brief, a Ply is first selected in the data tree for which the flat outline is shown in the Flat Pattern window. Then, one or more 2-D DXF outlines may be loaded onto the same window, which are automatically draped and displayed in the 3-D model view windows. In this fashion, a combination of manual adjustments and automatic draping can help designers with ply creation or modification. The imported outlines may even be edited in-place on the 3-D model view windows, point by point. Strips may also be defined to match available material dimensions, simulating tape-laying or patch operations. Laminate Tools Tutorial 61/62 Anaglyph Ltd