Investigation of the mechanical performance of metal-composite joints

Composite materials are gaining the attention of several industries due to the high stiffness-to-weight and strength-to-weight ratios they offer. Especially in the automotive industry, demands on reduction of CO2 emissions is the major driving force towards lighter vehicles. To achieve that, composite reinforcement is a promising technology for weight reduction, increasing the stiffness and preventing local buckling. However, composite material structures can only be used if the mechanical properties of relevant joints can be evaluated by experimentally methods that are robust and gives reliable parameters, that can be used for simulating and designing components. Otherwise metals are preferred as candidate structural material. The main challenge in this master thesis is the establishment of adequate methodologies for the design and analysis of the joints between composite and steel materials. It is known that the joint is the most critical part within the assembly. Its failure might risk the integrity of the entire structure. Final results regarding to the joint quality are still far from expected. Fracture toughness values, such as GIC and GIIC, are lower compared with the objective. Hopefully, the main problem was identified. Metal treatment has been the main issue during this project and we must keep working in this area to improve the properties of the metal-composite joint with the final objective to produce hybrid body component in a near future. Concerning the future work, make an extra step during the hot stamping process would be interesting to study. Extra metal treatment, such as sandblasting or laser on the surface, could be useful for the mechanical performance of the metal-composite joint