Ultrasonic fatigue testing system combined with online nondestructive testing for carbon fiber reinforced composites
The fatigue properties of carbon fiber reinforced polymers (CFRP), especially in the Very High Cycle Fatigue (VHCF) regime, are rarely investigated so far. To analyze VHCF and failure mechanisms of CFRP a new ultrasonic testing facility for cyclic 4-point bending combined with online nondestructive testing was developed. The cyclic load is generated by an ultrasonic resonance facility with a frequency of 20 kHz at a stress ratio of R > 0.1. The investigated material is a carbon fiber reinforced polyphenylensulfide (CF-PPS). The fatigue loading is divided into pulse and pause sequences to keep the specimens well below glass transition temperature. The fatigue status of the specimens will be observed online during ultrasonic cyclic loading and additionally be characterized offline during the loading pauses via thermography, Laser Doppler Vibrometry, microwave as well as linear and nonlinear ultrasonic techniques.