COMPARING SIMULATION OF SANDWICH MATERIAL IN COMPARE WITH EXPERIMENT SVOČ FST 2016

Transcription

1 COMPARING SIMULATION OF SANDWICH MATERIAL IN COMPARE WITH EXPERIMENT SVOČ FST 2016 Ing. Milan Tančin, University of West Bohemia in Pilsen, Univerzitní 8, Pilsen Czech Republic ABSTRACT This article is about comparing simulations of sandwich material and its part (outer layer). The goal is to create the material model and its part identically with the material, which was used for the experiment. Further steps are comparing these simulations with a real experiment. For these simulations is used software Siemens NX. Simulations are divided into two sections. The first section is about the tensile test of the fiberglass outer layer. Fibres are oriented at 0, 45 and 90 degrees. The second section is about three point bend test of whole sandwich material. For simulations from the both sections are selected volume elements (3D mesh). Simulations are solved by nonlinear solver. Some of the material values are based on the determination by optimization for this computation model. In this article, there are compared results of these simulations with the experiment. KEYWORDS Sandwich, simulation, tensile test, three point bend INTRODUCTION The goal of this article is comparing simulations of whole sandwich material and its outer layer. Material parameters and simulations results are known. In case of bigger differences between simulation and experiment, there will be commented reason. 1. TENSILE TEST OF THE FIBERGLASS OUTER LAYER 1.1 Introduction The main goal is a model of fiberglass outer layer, which is demonstrated in the report [1] and this model use for the same load and compare the results. Calculation was performed by nonlinear solver of the software Siemens NX 10. Outer layers with orientation 0, 90 and 45 degrees were tested. 1.2 Model creating Fig. 1 Specimens, tested in the report [1] The model was created as 3D mesh. There are divided faces for fixing and for loading and even divided face for determining elongation in required areas. Model will be the same for all simulations. Only material properties will be different.

2 Dimensions of two divided faces (l x w): 33.5 mm x 15 mm Start distance of the lever arm: 50 mm Dimensions of whole desk (l x w x h): 135 mm x 15 mm x 1 mm 1.3 Mesh Fig. 2 Created model The mesh was created as 3D mesh. Element type was CHEXA 8 and its size was 2.5 mm. Density of the mesh was reduced to reach two elements on thickness. Material was set as orthotropic with thickness 1 mm. Numerical values of every single parameter are shown in table below. Fibre orientations are different (0, 90 and 45 degrees). Values E1, E2 and G12 are results of the optimization for this computation model. The reason for a big reduction the G12 module is impossibility to approximate the nonlinear course dependence elongation loading in case with angle of fibres 45 degrees. 1.4 Simulation setup Fixing remove all degrees of freedom Loading area dependence elongation - time Fig. 3 Meshed model Setup of dependence elongation time is for case with fibre orientation 0 and 90 degrees the same. Simulation with fibres 45 degrees has different setup, due to bigger premise of the elongation during the simulation.

3 0, Fig. 4 Setup, dependence elongation - time 1.5 Results The results of all computing variants are presented by graphs, which show original data and simulation Results variant 0 Outer layer tensile test 0 deg Original data Simulation Difference 0, ,80 0, ,4-2,3 0,5 2181,80 0, ,8 0, ,60 0, ,7-0, , # 4,6 Fig. 5 Results - layer, fibres 0

4 1.5.2 Results variant 90 Original data Outer layer tensile test 90 deg Simulation Difference 0, ,5 0, ,4-7,7 0,5 2473,3 0, ,5 0, ,9 0, ,7-1, ,1 # 4, Results variant 45 Fig. 6 Results - layer, fibres 90 Outer layer tensile test 45 deg Original data Simulation Difference 0,5 598,84 0,5 151,4-295, , ,7-146,4 1,5 824,6 1, , , ,4-48,6 2,5 922,68 2,5 756,8-21, , ,4-3,9 3,5 965,2 3,5 1059,5 8, , ,8 # 20,0 Fig. 7 Results - layer, fibres 45

5 1.6 Partial conclusion For outer layers with fibre direction 0 and 90 degrees, maximal deviations are 10%. For outer layers with fibre direction 45 degrees there are big differences. It is caused due to lack of information about nonlinear material behaviour for fibres with this orientation. The further steps were to approximate nonlinear course. The main influence on this approximation had G12 module. Without this adjust, dependence loading elongation would be very different from original data and course would be the same as original data from 0 to 0.5 mm in whole range. It means, for bigger elongation it would be much bigger loading. 2 Sandwich material 3 point bend test 2.1 Introduction The main goal was 3D model of the sandwich material, which was evaluated in the report [1] and test the same loading and compare the results. Calculation was performed by nonlinear solver of the software Siemens NX Model creating Fig. 8 Three point bend test - experiment Model was created by stand - alone solids pro outer layers and for filling. Stand - alone model was used also for loading cylinder and for supports. For defining constrains, the planes were divided. Outer layers (l x w x h): 330 mm x 50 mm x 1.2 mm Filling (l x w x h): 330 mm x 50 mm x 10.1 mm Cylinder (diameter x w): 30 mm x 50 mm Start distance arms of the extensometer: 60 mm Fig. 9 Created model 2.3 Mesh Mesh was created as 3D swept mesh. Element type was CHEXA 8 and its size 2.5 mm. Material for outer layers was set as orthotropic, thickness 1.2 mm. Filling was set as isotropic material, thickness 10.1 mm. Numerical values of every single parameter are shown in table below. It is necessary to mention, that Young modules E1, E2 and G12 for material of outer layers were adjusted with respect to results of the original report. These values were optimized with respect to this computing model and it is necessary to slightly adjust these values with respect to this model. In this case, the values E1, E2 and G12 are the same as in the previous case (simulation of the tensile test for outer layers).

6 Contact Loading area, dependence elongation - time X axis Move restriction X axis Fig. 10 Model fixing and defining of the load area 2.5 RESULTS: Original data Sandwich 3 point bend test Simulation Difference 1 69, ,7 20, , ,7-1, , ,7-8, , ,8-10, , ,8-10, , ,8 # -8,7 Fig. 11: Results 3 point bend test 2.6 Partial conclusion The biggest deviations during simulation were only to elongation to 1 mm. After that, the results are in the required deviations. Possible influence is approximated value of the G12 module.

7 CONCLUSION In this article, there are compared results of the simulation for fiberglass outer layer with various fibre orientation and the sandwich beam in compare with the experiments. From partial conclusions is evident, that specified values for define the same task, like an experiment, are sufficient only particularly. It is necessary to know also nonlinear material characteristic. As a solution can be to use optimization processes, determine the material characteristic and use it during the simulation. Results in this report are approximations the experiments. The most important values for reach the best match were following: E1, E2 and G12. These values are valid for certain case with certain mesh. G12 module was much modified due to reach the best approximation of nonlinear characteristics during loading. These tests are useful to understand the material behaviour during loading. These knowledges are necessary for solving more difficult cases. ACKNOWLEDGEMENT By this way I would like to thank mainly to Tomáš Mandys for results supply from measured real specimens and valuable advices during creating the simulation and results evaluation. REFERENCES [1] Mandys, T. a Laš, V. & Kroupa, T. Identification of material parameters of sandwich composite panel, [2] Mandys, T. Kroupa, T. Las, V. Progressive failure analysis of composite sandwich beam in case of quasistatic loading. University of West Bohemia in Pilsen, [3] Laš, Vladislav. Mechanika kompozitních materiálů. Plzeň : Západočeská univerzita, ISBN X. [4] Mandys, T. Výsledky měření potahu a sendvičového materiálu. [5] Siemens. NX Help: Siemens Product Lifecycle Management Software Inc., [6] Vyhodnocení měření