Effects of post-welding cooling rate on strength of TCW joints: An experimental and numerical investigation

In a thermoset composite welding (TCW) joint, a thermoplastic weld polymer is used to allow two carbon-epoxy components to be welded together, where thermal residual stresses can build up due to high mismatch in coefficient of thermal expansion. In this study, the effects of the cooling rate on joint strength were investigated experimentally and numerically for its effect on thermal residual stresses in the TCW joints. The experimental results showed that, by lowering the cooling rate, a higher joint strength can be obtained across different operating temperatures and different laminate configurations. It is believed that the material properties of the thermoplastic weld polymer had been altered by the use of different cooling rate and damage zone method was used in the numerical model to predict the material properties of the weld polymer. The numerical results confirm that the lower cooling rate produced weld polymer with higher strength and stiffness, which translated into a stronger TCW joint. The combination of experimental work and FEA model in this study allows the prediction of joint strength when the material properties are not widely available due to post-manufacturing treatment.