Temperature distribution inside composite and fiber metal laminates during modified cure cycles

Manufacturing-induced thermal residual stresses reduce the mechanical strength of fiber metal laminates (FML). Modified (MOD) cure cycles can help to reduce these stresses. However, the typically assumed homogeneous temperature distribution across the thickness of a laminate may not hold true for laminate configurations with, e.g., large thicknesses or low thermal conductivity. Therefore, the temperature in monolithic composite and fiber metal laminates is experimentally determined. Based on the experimental results, a numerical heat transfer model is developed to predict the temperature throughout the cure cycle. A good agreement between experiment and simulation is achieved. The numerical model further shows that temperature gradients of up to 20 °C for a 40 mm thick laminate can be expected, which will significantly influence the homogeneity of the residual stress state in such a laminate manufactured with a MOD cycle. The numerical model can serve as a valuable tool for estimating the homogeneity of the temperature distribution across the thickness of a laminate for different layups and cure cycle modifications.