Three Point Bending Fatigue of Carbon Fiber Fabric Reinforced Polyphenylensulfide in the Very High Cycle Fatigue Regime

Abstract

Carbon fiber reinforced polymers (CFRP) are getting more and more important for structural components for automotive and aerospace applications. These components are subjected to 1011and more loading cycles during their time in service. Therefore the VHCF behavior and the corresponding failure mechanisms have to be well understood. To obtain a comprehensive knowledge about the fatigue behavior and failure mechanisms of CFRP in the VHCF regime, a new Ultrasonic Testing Facility (UTF) for cyclic 3-point bending at 20 kHz has been developed at WKK. This UTF with combined online nondestructive testing via laser vibrometry and IRthermography enables VHCF experiments up to 109cycles in twelve days without overcritical heating up to the glass transition temperature of the polymer. The chosen material in this research project is the commercially available and aircraft qualified carbon fiber fabric reinforced polyphenylensulfide (CF-PPS). To determine the fatigue characteristics of CF-PPS load increase tests and based on these results constant amplitude tests up to 109cycles have been carried out. Light optical and SEM microscopy have been performed in defined fatigue states or finally after reaching 109cycles with shear stress amplitudes of at least 44% of the monotonic ultimate shear strength. The induced fatigue damage of CF-PPS in the VHCF regime was studied in detail.