Development of Optical Coherence Tomography for the Measurement of the Surface Wrinkle of Composite Parts

Transcription

1 Development of Optical Coherence Tomography for the Measurement of the Surface Wrinkle of Composite Parts Yoshiharu KUZE Composite Laboratory Manufacturing Technology Research Department May 9,

2 Table of Contents 1. Background 2. What is OCT? 3. Development of OCT Method 3.1 Feasibility Study 3.2 Implementation to Production Parts 4. Summary 2 2

3 Table of Contents 1. Background 2. What is OCT? 3. Development of OCT Method 3.1 Feasibility Study 3.2 Implementation to Production Parts 4. Summary 3 3

4 1 Background Composite Parts Manufacturing Process Lay Up Set Up Bagging Curing Debagging Trim / Drilling Inspection Example of Inspection NDI (Internal Defect) Dimensional Inspection Visual Inspection Today s Topic e.g. Foreign Object Debris, Scratch, Surface Wrinkle What is surface wrinkle? Cross-section Image Surface fiber waviness Filled with resin Occasionally occur around complex shape areas Sometimes stress critical Need to know wrinkle depth Existing NDI methods cannot measure the wrinkle depth. (e.g.) UT: No reflection from the interface between resin and fiber. How do we measure now? 4 4

5 1 Background Current measurement Method for wrinkle depth Method Comparative Visual Inspection Cross-sections Measurement Depth Gauge Overview Compare parts to sample Cut the part and measure with microscope Remove resin and measure depth using depth gauge Advantage Low cost Very accurate Accurate & practical Disadvantage Individual variation Qualitative approach Cannot apply to production part High Inspection Cost Need rework e.g. Depth Gauge Method Now Wrinkle occur Wrinkle part Resin removal Be careful not to damage Depth measurement Depth gauge Failure Repair or Reject Repair Next process Accept Urgent Need Quantitative Evaluation Low Cost Method OCT Method will meet these requirements. 5 5

6 Table of Contents 1. Background 2. What is OCT? 3. Development of OCT Method 3.1 Feasibility Study 3.2 Implementation to Production Parts 4. Summary 6 6

7 2 What is OCT? What is Optical Coherence Tomography (OCT)? Feature Tomography range: Max. 4-5 mm ( in.) from surface (Infrared-transparent Material) Higher resolution compared with Ultrasonic (to µm) High-Speed, 3D Imaging Non-contact, Non-invasive Other Precedents Funduscopy (Retinal Detachment, etc.) Example of OCT measurement Cornea Iris Vitreous Retina Sclera This technology will improve... Target Wrinkle occur Wrinkle part Anterior Segment Depth measurement (Non-destructive) OCT measurement system Accept Posterior Segment Next process measurement image Failure Repair or Reject 7 7

8 2 What is OCT? Measurement OCT: Realize real-time measurement due to Swept-Source method. Target Effect Reduce the measurement time (including repair):90% of Inspection Cost Reduction Now Wrinkle occur Cause of wrinkle Vf Abnormality hot compaction problem, etc. Resin removal Be careful not to damage Depth measurement Depth gauge Failure Repair or Reject Repair Next process High Cost Wrinkle part Accept 90% reduction OCT measurement system Depth measurement (Non-destructive) Accept Next process Target Low Cost measurement image Failure Repair or Reject 8 8

9 Table of Contents 1. Background 2. What is OCT? 3. Development of OCT Method 3.1 Feasibility Study 3.2 Implementation to Production Parts 4. Summary 9 9

10 3 Development of OCT Method START Feasibility Study (3.1) Evaluation of error Measurement Error: Difference between microscope and OCT measurement Target Accuracy: Within + or - 0.1mm (0.004 in.) Error Target Value Yes Implementation to Production Parts (3.2) Incident angle Surface roughness Environment and material condition No Not available Incident angle: Influence of saturation noise Surface roughness: Influence of signal amplitude Condition: Influence of refractive index UV Establish Spec. Ready for using Resin Incident angle Surface roughness Minute bubble Condition 10 10

11 3.1 Feasibility Study START Feasibility Study (3.1) Evaluation of error Error Target Value Not available Implementation to Production Parts (2.4) Incident angle Surface roughness Environment and material condition Establish Spec. Ready for using JCAB approval is needed 11 11

12 3.1 Feasibility Study Evaluation of Measurement Error: Compare OCT data to DI cross-sections data Measured about 30 points data Measurement error = OCT data microscope data Measurement point Measure depth by peak to peak Tomography by OCT Measurement Error Cross-sections OCT data of measurement point Sample mean and Standard Error Sample mean = mm ( in.) Systematic Error, e.g. micrometer and refractive index measurement measurement by microscope Standard Error = mm ( in.) 95% confidence of measurement Comparison between OCT and microscope 0.013±0.043mm (= 0.013± ) ( in. ± in.) Measurement Accuracy Estimation: ±0.06mm Target Value (±0.1mm) ( in.) (0.004 in.) 12 12

13 3.2 Implementation to Production Parts START Feasibility Study (2.3) Evaluation of error Error Target Value Not available Implementation to Production Parts (3.2) Incident angle Surface roughness Environment and material condition Establish Spec. Ready for using JCAB approval is needed 13 13

14 3.2 Implementation to Production Parts Allowance of Incident Angle Why incident angle is adjusted? Noise = Signal saturation due to specular reflection of Infrared Target angle: 4 ±1 degree Aimed for in feasibility study Noise NG e.g. Incident Angle: 0 degrees Noise Signal OK 3 degrees 4 degrees Angle Holding Jig 5 degrees Incident Angle: 3 degrees Signal Noise Incident Angle: 4 degrees Signal Noise Incident Angle: 5 degrees OK OK No significant difference between 3-5 degrees. Established requirements of Incident Angle and Holding Jig 14 14

15 3.2 Implementation to Production Parts Allowance of Surface Roughness None #800 #600 #400 #240 #120 Using several grit size sandpaper smooth None OK OK Surface signal strength does not change due to surface roughness Back wall signal strength is reduced due to surface roughness Signal reduction leads to Signal to Noise Ratio degradation #600 Ra:0.7µm,RMS:0.9µm rough NG #120 Ra:2.6µm,RMS:3.3µm Surface Back wall 15 Established requirements of surface finishing 15

16 3.2 Implementation to Production Parts Allowance of Environment and Material Condition Environment : UV efficient, Moisture absorption Material : Thermoplastic powder, Minute bubble Is the refractive index affected by material condition? No. Condition Description refractive index 1 Plain VaRTM Resin Moisture 80 C hot bath, 0.03wt% Minute bubble No degassing, when mixing T/P 1.5wt% Nominal amount T/P 3.0wt% Deviation UV 24Hr Leaving in room UV 72Hr Leaving in room UV 69.8kJ/m 2 Equivalent of 1 week storage UV 138.6kJ/m 2 Equivalent of 2 week storage UV 98.0kJ/m 2 Equivalent of 1 month storage UV 570.1kJ/m 2 Equivalent of 6 month storage UV kJ/m 2 Equivalent of 1 year storage UV kJ/m 2 Equivalent of 3 year storage Result of refractive index measurement Max , min % different between measurements No significant difference between all conditions Established requirements of reference standard storage and annual check No. 16

17 3.2 Implementation to Production Parts Measurement Specification: Established the requirement from examinations. Ø Incident Angle Ø Surface Roughness Ø Storage and Annual check Established other requirement (material handling, actual measurement, etc.) Ø Discuss with Design, Manufacturing and Quality assurance sections Ready to use for production parts Future Work: How to measure the wrinkle on the complex shape? Ø Corner Radii Ø Kink, Near by Step Area Ø Rough Surface Area 17 17

18 Table of Contents 1. Background 2. What is OCT? 3. Development of OCT Method 3.1 Feasibility Study 3.2 Implementation to Production Parts 4. Summary 18 18

19 4 Summary 1. Feasibility study was done on OCT which can measure the resin thickness with non-destructive, high-speed, and highly accuracy. 2. Established OCT method for aerospace composite parts. 3. Ready to use for the production parts

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