The analysis of residual stresses in layered composites with [0°/90°] layup

Recently an increased attention has been paid to the deep understanding of the processes caused by residual stresses in laminated composites, specifically, shape distortion and possible product damages at the stage of manufacturing. The presence of residual stresses in a composite material affects the occurrence of such defects as delamination, warping, as well as the appearance of microcracks in a matrix of a material, which has a significant impact on the static and fatigue strength of the product made of composite materials. This paper considers a change in the distribution of the residual stress field in a specimen from the known material AS4/8552-1 with the layers [0°/90°]n in the curing process and the stresses on the free edge after the cut of the sample along the reinforcement direction. The curing model is numerically implemented using ABAQUS finite element modeling package with special user subroutines. The coupled thermal and strength problem under plane strain conditions is solved to model the curing. A significant difference in residual stresses at the free edge before and after the mechanical cutoff is shown. Computed residual stresses are further used to analyze the development of the composite fracture under uniaxial tension. As a result of modelling the loading of the composite up to failure with a consideration of the residual stresses, it is shown that tension leads to cracking of the matrix in layers where the orientation of the reinforcement coincides with the direction of the load application. At the same time, when ignoring residual stresses, the appearance of such defects is not observed. This research shows that residual stresses affect both the strength of the material and the mode of failure.