Processing induced residual stress in asymmetric laminate panels

In this research, a one-dimensional finite difference model has been develo ped to simulate the progression of material properties during the processin g of metal-clad, multi-layered, fiber mat reinforced, thermoset resins. Usi ng a micro-mechanical model, the simulation is also capable of predicting t he dimensional movement observed during processing and the through-thicknes s residual stress distribution within thin laminates that will lead to the development of warpage or curling. The ability to predict the overall movem ent is quite complex; however, the contributing factors that lead to warpag e of epoxy, glass-fiber mat laminate composites have been experimentally an d numerically identified. It has been found that the dominant factor that l eads to warpage in asymmetric multi-layered laminates is the differences in the coefficient of thermal expansion of the individual plies. Thus, by sel ecting appropriate combinations of the degree of cure and resin content of the thermoset in the individual plies, it is possible to reduce the materia l property variability of the laminate through thickness. The planar moveme nt of individual plies is a function of the glass-fiber mat tension during pre-processing operations. Variability in pre-processing mat tension can be compensated for after lamination via post-baking processes.