Improvement of an adhesive joint constructed from carbon fiber-reinforced plastic and dry carbon fiber laminates

The staircase joint is an adhesive joint constructed using stepped carbon fiber-reinforced plastic (CFRP) fabric, half molded with dry carbon fibers. In this adhesive joint, the CFRP part is fabricated first, then remolded with dry carbon fiber laminates. Some improvements are provided to enhance performance in terms of tensile strength. These improvements include the addition of extra carbon fiber covers and overlapping the carbon fiber half over the CFRP. This paper introduces three adhesive joints: the first is the original staircase joint and the other two are improved staircase joints. All joints and CFRP fabrics were made in our laboratory using vacuum-assisted resin transfer molding (VARTM) manufacturing techniques. Specimens were prepared for tensile testing to measure joint performance. The results showed an improved tensile load for the modified staircase joints. For example, the total percentage increase in the tensile load was 39% for five-carbon-fiber-layer CFRP. The final joining efficiency reached 59% for seven-carbon-fiber-layer CFRP. However, the tensile fracture behavior of all joints showed the same pattern of cracks, originating near the joint ends, followed by crack propagation until fracture.