Fatigue Prediction in Vibration for  Short Glass Fiber Reinforced Composites

Fatigue Prediction in Vibration for

Short Glass Fiber Reinforced Composites

Lang Dong^1*, Haiquan Zhang², Christine Roucoules³, Kai Chen⁴

^{1, 4}Valeo Lighting Hubei Technical Center Co., Ltd, Wuhan, China, 430014

²Valeo Ichikoh (China) Auto Lighting Co., Ltd Foshan Branch, Foshan, China, 528000

³Valeo Lighting Systems, Bobigny, France, 93012

*Contact email address: lang.dong@valeo.com

Abstract- In automotive lighting design, fatigue behavior is an important parameter for the reliability of products. Plastic with short glass fiber is widely used to reinforce the components and increase the fatigue lifetime in vibration. Short glass fiber reinforced composites have anisotropic mechanical properties and fatigue behavior. To improve the accuracy of fatigue life prediction for short glass fiber reinforced composites, coupling of injection simulation with fatigue analysis in vibration simulation was done in this paper. Two approaches were compared: a damage calculation was based on an equivalent Young’s modulus and on a glass fiber mapping. Injection simulation was done on a part reinforced with short glass fiber to output the fiber orientation. Glass fiber orientation coupling from rheology was mapped in mechanical simulation to get the exact plastic with fiber. Damage analysis was done in harmonic and random vibration on two parts integrated in a product. One was a structural bracket supported in an optical module alone, the other one was a headlamp product. To predict the fatigue behavior of the part reinforced with short glass fiber, stress, fiber orientation and   SN curve of plastic fiber were used. Analysis of damage was applied on an equivalent Young’s modulus part and, on a fiber oriented part based on the fiber oriented SN curves and the master SN curve. Predictions of damage in vibration were compared to test results in harmonic and random vibration. Damage on the short glass fiber reinforced part is giving a better reliability prediction versus test than a classical analysis of equivalent von-Mises stresses compared to fatigue limit or equivalent isotropic young modulus.

  Keywords: fatigue, glass fiber, isotropic, anisotropic, vibration, injection coupling, SN curve