Investigation of Formability and Fiber Orientation in the Square Deep Drawing Process with Steel/CFRP Hybrid Composites

Recently, vehicle parts such as center pillars and impact beams used in automobiles have been requiring materials that satisfy both high strength and impact absorption. Therefore, in this study, the applicability of the forming process of CR340 (cold rolled steel sheet)/carbon fiber reinforced plastic (CFRP) hybrid composites which are a bonded material of cold rolled steel sheet having excellent formability and carbon fiber prepreg having high strength and high collision absorption in the vehicle parts was investigated. Hybrid composites are fabricated by stacking CFRP prepreg on a cold rolled steel sheet (CR340) with Zn coating. Bonding materials were used at the interface between the CFRP prepreg and steel sheet. This study investigated the formability and fiber orientation of CR340/CFRP hybrid composite after deep drawing. Square cup deep drawing tests were conducted with various process parameters to evaluate the formability of CR340/CFRP hybrid composite. The square deep drawing process parameters and the thinning rate at each position of the drawing product were measured, and the various problems encountered during the deep drawing process were reviewed with the thermal flow of epoxy. Experimental data between the forming depth and blank holding force was introduced with CFRP/CR340 with Zn coating sheet hybrid composite. The thickness variations of the materials and the fiber orientations were observed using cross sections at each position. Void and delamination defects were observed at the die round and were discussed in detail.