Effect of fatigue loading rate on lifespan and temperature of tailored blank C/PPS thermoplastic composite

This article reports an experimental investigation of the effects of the loading frequency on the temperature change, fatigue behaviour, and failure mechanisms of carbon-fibre-fabric-reinforced polyphenylenesulphide (PPS) laminates, the thicknesses of which were varied by ply drops. The experiments specifically considered two ply drop configurations and fatigue loading frequencies of 0.5-15 Hz. Fractographic examination revealed the presence of loading-frequency-based surface fracture features in the tested specimens. With increasing loading frequency, the local temperature also increases significantly, reaching as high as above 110 °C, accompanied by more than one order of magnitude decrease in the fatigue life. For a surface temperature of up to 38 °C, there was no specific relationship with the fatigue life. However, further increase of the surface temperature up to and beyond 75 °C was accompanied by significant reduction of the fatigue life. An analytic relationship between the load rate and the local temperature was derived and used to define limits for the fatigue testing of tailored blank structures.