Residual stresses near the free edge of composite materials

The accumulation of residual stresses during the manufacturing of a carbon-epoxy composite induces defects such as interlayer delamination and the formation of microcracks in the matrix. In the present study, the effect of the polymerization process in the thermoset matrix of the laminated composite plate on the stress state near the free edge is investigated. To estimate the residual stresses in the laminate, the simulation of the curing process was accomplished using coupled thermal and structural analysis. The proposed approach was implemented in ABAQUS software via a special user subroutine, and the validation problem of plate distortion after the curing is presented. The modeling of the cut process was performed, which corresponds to the plate machining, for the analysis of the residual stress re-distribution after the cut with formation of a free edge. In addition, the manufacturing process of the laminate with the initial crack was simulated for the analysis of crack growth caused by residual stresses. Finally, the modeling of uniaxial load to the laminate up to failure with the presence of residual stresses and consideration of a crack in the vicinity of the free edge is presented.