Measurement and simulation of residual stresses in laser welded CFRP/steel lap joints

In light of the demand for reducing the emission of climate-damaging gases such as CO2, it is very important to apply lightweight materials in the aerospace and automotive industries. In the past years, hybrid structures made of carbon fiber reinforced plastics (CFRP) and metals received high attention from numerous industries. Laser welding is an advanced approach for bonding dissimilar materials. However, in the welding process, residual stresses are induced in the joined part, which influence the mechanical performance of the bonded components. In the present work, residual stresses in laser welded CFRP and steel joints are experimentally determined using the hole drilling method (HDM) and numerically analyzed by thermal elastic-plastic finite element analysis. The non-uniform residual stress distribution through the thickness direction of the CRRP and steel plates can be successfully measured when the anisotropic material properties in CFRP are considered. Moreover, a numerical simulation was carried out for analyzing the residual stresses in the laser welded CFRP/steel joints, particularly their distribution characteristics at the CFRP/Steel interface. Specific discussions focus on the residual stress formation mechanism and the effect of laser welding process parameters on the residual stresses through experimental tools and numerical simulations.