Testing and modelling the fatigue behaviour of GFRP composites – Effect of stress level, stress concentration and frequency

Abstract

The effects of stress level, stress concentration and frequency on the fatigue life of glass fibre reinforced polymer (GFRP) composites have been investigated under tension-tension fatigue at a stress ratio of 0.1. Vinyl ester-based GFRP laminates were tested at a stress level of 80%, 70%, 60%, 50%, 40% and 25% of the ultimate tensile strength until the failure or up to 8 million cycles whichever comes first in order to determine fatigue life and identify failure modes. The results showed that the composites failed in pure tension at high applied stress while the failure was dominated by stress concentration at low stress level. Moreover, stress concentration was found to reduce the fatigue life of the laminated composites and the test frequency of up to 8 Hz did not induce excessive self-heating. The mean stress failure criteria was found appropriate for numerical modelling of GFRP composites subjected to low level of stress while Goodman failure criteria is suitable at high stress condition. The analytical model considering the effect of stress ratio, applied maximum stress, frequency and material properties is able to predict reliably the fatigue life of GFRP composites in tension.

Keywords

• Glass fibres
• Stress concentration
• Failure theory
• Analytical model