Design and Analysis of a Novel Carbon Fiber Reinforced Polymer Sandwich Adhesive Joint

Composite sandwich structures are widely used in transport and energy applications because of their excellent specific strength and fatigue damage resistance. However, the mechanical properties of the joint area rely on the structural design. This paper proposes a novel carbon fiber-reinforced polymer sandwich joint in the context of a Formula Student monocoque. A stiffener is introduced to connect carbon fiber panels on both sides, and the geometry of the aluminum honeycomb connecting core is adjusted to improve the stress distribution in the joint panels. A finite element model under a three-point bending load is established based on the progressive damage model and the cohesive zone model. The mechanical properties were compared with conventional joints based on Formula Student three-point bending tests. Specimens were fabricated and tested using t700 carbon fiber prepreg and 3003 aluminum honeycombs to verify the joint’s performance and the accuracy of the finite element model. Experimental results showed that the three-point bending strength of the novel joint increased by 52.27 % , and the stiffness increased by 101 % compared to the conventional design. The simulated strength errors of the novel joint and the conventional joint were 4.66 % , and 13.7 % , respectively, and the failure modes were consistent with the experimental results, indicating the validity of the finite element model. The novel joint profile is less protruding than the conventional joint and could be widely used for joining or repairing automotive and aircraft components.