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Injection Molding Fiber Orientation, Property Predictions, and Failure Analysis

Injection Molding Fiber Orientation, Property Predictions, and Failure Analysis. Presented by Robert Sherman Senior CAE Analyst, RTP Company. What We’ll TRY to Cover. Source of Fiber Orientation What Causes it New AMI 2012 Analysis Features RSC Factor & Its Effects

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Injection Molding Fiber Orientation, Property Predictions, and Failure Analysis

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  1. Injection Molding Fiber Orientation, Property Predictions, and Failure Analysis Presented by Robert Sherman Senior CAE Analyst, RTP Company

  2. What We’ll TRY to Cover • Source of Fiber Orientation • What Causes it • New AMI 2012 Analysis Features • RSC Factor & Its Effects • Modulus (& Stress) Predictions • Without RSC • Various RSC Factors • Improved Stress Predictions

  3. Structural Composites from the Injection Molding Process • Injection molding products are being utilized in increasingly structural applications • To date, analysis has consisted of quasi-isotropic analysis • Quasi-isotropic analysis CANNOT optimize orthotropic materials properly • Orthotropic analysis requires failure analysis and strength allowables • What can be utilized???

  4. Structural Composites from the Injection Molding Process • Sensible approach to the problem: Composite laminate analysis • Injection molded materials can be treated like continuous fiber composites • Problem : Infinite number of orientations! • Systematic approach for evaluation is needed in order to prevent unexpected failures • Linear material approach initially

  5. What Causes Fiber Orientation ? • Two primary forces • High shear rate & velocity gradient through part thickness • Extensional forces in flow front expansion and contraction • Fiber orientation is “history” dependent – effects are cumulative as polymer flows from gate to end-of-flow

  6. What Causes Fiber Orientation ?

  7. What Causes Fiber Orientation ?

  8. What Causes Fiber Orientation ?

  9. Fiber Orientation • Shearing forces in outer laminates • Expansional/contractional forces in middle laminates • Changing flow directions during fill/pack • Orientation behavior is sum of the cumulative effects

  10. Autodesk® Moldflow® InsightNew Analysis Features • Fill Preview (real-time fill prediction solver) • Inventor Fusion Interface for model simplification • Transient cooling analysis • Venting analysis • Long fiber orientation capability (ARD model) • Short fiber orientation improvements (RSC model)

  11. Reduced Strain Closure (RSC) Factor • All fiber orientation predictions previously were fully developed “steady state” orientation • Reality – orientation takes time to fully develop • RSC factor introduced to control the rate of development of orientation • Problem: limited validation to date (Delphi; 2 PBT materials) • Take “cup half-full” approach

  12. How Can We Validate Fiber Orientation ? • Qualitative validation can utilize microscopy • Made quantitative with shape recognition software • Micro tomography analysis (Skyscan) • Simpler (cheaper) method of validation needed for number of materials needing validation • Utilize tensile modulus predictions and measurements as “first cut” validation • Later confirm with flexural stiffness verification

  13. What does RSC Factor Do?

  14. Look at Molded Tensile Bars First

  15. Flow Direction Modulus (RSC=1.00)t = 3.05 mm (0.120 in)

  16. Modulus Transverse to Flow (RSC=1.00)t = 3.05 mm (0.120 in)

  17. Flow Direction Modulus (RSC=0.15)t = 3.05 mm (0.120 in)

  18. Modulus Transverse to Flow (RSC=0.15)t = 3.05 mm (0.120 in)

  19. Flow Direction Modulust = 6.35 mm (0.250 in)

  20. Modulus Transverse to Flowt = 6.35 mm (0.250 in)

  21. Laminate Stress Analysis

  22. Summary • RSC factor clearly seems to improve the fiber orientation predictions • More correlation is needed (flexural modulus) • Other possible influencing factors may need improvement • Relook at fiber A/R utilized (usually too low) • Other boundary conditions • More materials to determine factors influencing RSC

  23. Thank You! Presented by Robert Sherman Senior CAE Analyst, RTP Company rsherman@rtpcompany.com

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