Fatigue behaviour and damage evolution of glass fiber reinforced composite material

The proposed extensive use of advanced fiber-reinforced composites in structural applications such as large marine vessels has brought attention to the need to be able to predict the fatigue life of these structures. For design purposes, it is important to be able to predict when fatigue cracks initiate and the duration of the propagation phase before rapid final failure occurs. A fatigue study has been conducted as part of the FIBRESHIP Horizon 2020 funded EU project. This paper addresses one aspect of the fatigue study conducted in FIBRESHIP, focusing on suitable methods to identify crack initiation and monitor the subsequent crack propagation in glass fiber reinforced composite materials (GFRP) under fatigue loading. To correlate the fatigue response with the crack initiation and propagation phases, interrupted fatigue tests were carried out on open-hole GFRP test samples. The reinforcing fibres were predominantly transverse to the loading direction. Fatigue tests were periodically interrupted and stiffness measurements were performed to track the evolution in stiffness as a function of the number of fatigue load cycles. Damage was also monitored using ultrasonic scanning to inspect the progressive failure morphology of the matrix and reinforcing fibres. It was found that the first type of damage that appears in 90° plys under loading is matrix cracking.