Flexural fatigue damage and life prediction of rod-shaped pultruded fibre-reinforced composite: Progressive damage model and acoustic emission measurement

This study proposes an improved progressive fatigue damage model. The relation between cyclic property degradation and direction is established. The fatigue damage evolution and life of rod-shaped pultruded fibre-reinforced composite (PFRC) under three-point bending are investigated using the proposed progressive fatigue damage model and acoustic emission test. The damage and failure mechanisms of PFRC are elucidated. Results show that the fatigue damage evolution and life can be predicted accurately by the proposed model. For PFRC under high load levels, delamination is the dominant failure mode; by contrast, the failure of PFRC under fatigue load not higher than medium–high level is dominated by matrix cracks and fibre fracture. The area of flat fracture is related to load level. The sequence of each damage mode appearing in each layer differs. Because the stress distribution in each single layer of PFRC under three-point bending load is not uniform, the delamination and fibre fracture only occur after the matrix crack of the corresponding local area reaches saturation, instead of occurring after the matrix crack of the whole specimen reaches saturation.