LAUSR

Abstract This study was performed to investigate the feasibilities, characteristics and mechanisms of laser bonding heterogeneous joints from thermoset carbon fiber reinforced sheet molding compound (SMC) and dual-phase steel (DP590) with the aid of an intermediate polycarbonate (PC) mid-layer. The single lap-joint showed that the load at failure reached up to 3.31 kN (i.e. 4.9 MPa for shear strength). Morphological analysis of four fracture modes as well as mechanical characterization of the heterogeneous joints were carried out to understand the effect of laser line energy on the joint quality including defects and strength. By analyzing the relationship between the area percentage of four fracture modes and ultimate shear force (USF) of the joints with various line energies, the contribution of each fracture mode to the joint strength was determined and discussed. In addition, cross-sectional analysis indicates that bubble expansion caused by SMC substrate degradation results in carbon fibers being squeezed into molten PC, which increases the bonding area by creating wavy contacts and generates a mechanical interlock at the SMC/PC interface.