Fatigue Behavior of PP-LFT used in FEM Carreir with Variation of Stress Ratio

Abstract

Plastics have brought a significant progress in reducing the weight of automotive parts and improving gas emissions by replacing steel parts. The front end module (FEM) carrier, which was made from long glass fiber reinforced polypropylene (PP-LFT), is one of the most successful examples. On the other hand, more research on the fatigue behavior and vibration durability of automotive plastic parts will be needed to improve the long-term reliability. This paper analyzed the durability of the PP-LFT, which is fundamental to fatigue design and analysis of FEM carrier. Various fatigue tests were conducted at different stress ratios to evaluate the relationship between the fatigue life and stress amplitude or mean stress level. In the case of a fixed stress amplitude, the change in fatigue life with the stress ratio was 2∼6% larger than the case of fixed maximum stress. Furthermore, this study observed the mechanism of initiation and propagation of the fatigue cracks in PP-LFT by scanning electron microscopy.Key Words : Front end module carrier, long glass fiber reinforced polypropylene, fatigue behavior, stress ratio,

A review of Long fibre thermoplastic (LFT) composites

“…In addition to their quasi-static material properties and impact performance, the creep behaviour [266][267][268][269][270][271], fatigue behaviour [6,51,[272][273][274][275], vibration behaviour [276], UV resistance [277], machinability [278,279], heat treatment [280], and rheological behaviour [56,58,96,199,[281][282][283][284], of LFT composites have Table 1. Mechanical properties of LFT composites.…”