Determination of forming procedure by numerical analysis and investigation of mechanical properties of steel/CFRP hybrid composites with complicated shapes

In this study, a hybrid composite material was fabricated by stacking carbon fiber-reinforced plastic onto CR420 plates to increase the specific strength and stiffness relative to those of thick boron steel plates and dual-phase steels. Simulations were first used to compare and evaluate the abilities of two forming processes to manufacture appropriate center-pillar reinforcements. After determining the best process, a die was prepared using computer aided engineering (CAE), and a center-pillar reinforcement was formed with a carbon fiber-reinforced plastic (CFRP)/CR420 hybrid composite. The differences in the mechanical properties of the specimens were investigated according to their position using simulations. The specimen thicknesses in the experiment and simulation were compared. Positions where the contact pressure was low could be found in the simulation. Further, the reasons for the deterioration of the mechanical properties were elucidated by observing the micro-structure. Large quantities of voids with a size greater than 50 μm were found in those specimens that had a contact pressure lower than 0.5 MPa. The results obtained confirm that large quantities of voids cause the mechanical properties of CFRP composites to deteriorate.