Processing induced residual stress in asymmetric laminate panels

Abstract In this research, a one‐dimensional finite difference model has been developed to simulate the progression of material properties during the processing of metal‐clad, multi‐layered, fiber mat reinforced, thermoset resins. Using a micro‐mechanical model, the simulation is also capable of predicting the dimensional movement observed during processing and the through‐thickness residual stress distribution within thin laminates that will lead to the development of warpage or curling. The ability to predict the overall movement is quite complex; however, the contributing factors that lead to warpage of epoxy, glass‐fiber mat laminate composites have been experimentally and numerically identified. It has been found that the dominant factor that leads to warpage in asymmetric multi‐layered laminates is the differences in the coefficient of thermal expansion of the individual plies. Thus, by selecting appropriate combinations of the degree of cure and resin content of the thermoset in the individual plies, it is possible to reduce the material property variability of the laminate through thickness. The planar movement 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.