Optimal cure cycle parameters for minimizing residual stresses in fiber-reinforced polymer composite laminates

Abstract

The curing of a fiber-reinforced composite laminate in an autoclave generally induces residual stresses that may make the cured laminate curved. Here, we find optimal cure cycle parameters for asymmetric cross-ply laminates that (i) provide uniform and nearly complete curing of the laminate (i.e., the degree of curve is the same everywhere and equals at least 0.96) within a specified time period and (ii) minimize residual stresses without adversely affecting the transverse effective elastic modulus of the laminate. We simulate the cure process by using functionalities built in the commercial finite element software ABAQUS, the cure process modeling software COMPRO and the multi-purpose software MATLAB. After having satisfactorily compared the presently computed results for the curing of two laminates with either experimental or numerical findings available in the literature, we use a genetic algorithm and the Latin hypercube sampling method to optimize the cure cycle parameters. It is found that in comparison to the manufacturer’s recommended cure cycle (MRCC), for a cross-ply laminate with the span/thickness equal to 12.5, one optimal cycle reduces residual stresses by 47% and the total cure time from the MRCC time of 5 h to 4 h and another optimal cycle reduces the total cure time to 2 h and residual stresses by 8%. For the same cross-ply laminate with the span to thickness ratio of 125, an optimal cycle reduces the process induced curvature by 13% in comparison to the MRCC but increases the total cure time from 5 to 7.4 h. The approach presented here can be used by manufacturing engineers to obtain cure cycle parameters for fabricating composite laminates of desired quality.