Comprehensive Evaluation method of Bond Strength in Ultrasonic Welding for CFRTP

In this study, we propose a comprehensive method to evaluate the bond strength of ultrasonic-welded carbon-fiber-reinforced-thermosetting-plastic (CFRTP) considering combined stress state. Ultrasonic welding is one of the promising welding methods for CFRTP that are expected to apply to bonding large parts such as aircraft components, but this welding has not been generally applied because the quantitative evaluation method for bonding strength has not been established yet. In the present study, two types of fracture tests are proposed for ultrasonic-welded CFRTP with the goal of evaluating the strength of the adhesive interface considering the combined shear and tensile stresses. One is a 'compression shear test', which evaluates the strength when compressive stress is applied in the shear direction to the adhesive interface. The other is a 'flatwise test', which evaluates the strength when tensile stress is applied perpendicular to the interface. Finite element analysis (FEM) is used to simulate both tests to obtain accurate shear and tensile stresses, taking into account the combined stress state and stress distribution. Based on the above results, a quantitative and comprehensive evaluation of adhesive strength at the welding interface is attempt.