Study on the fractal dimension and evolution of matrix crack in cross-ply GFRP laminates

Abstract

Damage evolution and failure criterion are the focus of structural strength research in fiber reinforced plastic (FRP) composites. In this paper, quasi-static tests and fatigue tests at different stress levels of cross-ply glass fiber reinforced plastic (GFRP) laminates were carried out to obtain the stiffness degradation curves and matrix damage images. Based on the discovery that the matrix damage morphology has statistical self-similarity, the evolution of the matrix damage and its fractal dimension were studied. It is found that the evolution of matrix damage’s fractal dimension can be divided into three stages, and the fractal dimension of matrix damage corresponding to the characteristic damage state is independent of load type and stack sequence. When transverse crack initiation, transverse crack saturation and laminate failure occur, the fractal dimensions are Dbi = 1.39, Dbs = 1.81, Dbf = 1.90 respectively. Due to these advantages, the fractal dimension of matrix crack could be an appropriate damage state parameter.