Optimization design of the control arm of CFRP–aluminum foam sandwich structure

To meet the lightweight design requirements of the control arm, an automobile suspension control arm with a carbon fiber reinforced plastics (CFRP)–aluminum foam sandwich structure was proposed, and the structure optimization design of the CFRP panel was performed. The accuracy of the cellular pore model of aluminum foam hexahedron was verified by the quasi-static compression test of aluminum foam. The performance parameters of carbon fiber reinforced plastics were obtained by the mechanical property test of CFRP. A suspension control arm composed of a CFRP–aluminum foam sandwich structure body and an aluminum alloy connector was designed, and the adhesive-bolted hybrid joint was used to connect the two. Based on this, the finite element model of the control arm of the CFRP–aluminum foam sandwich structure was established. The porosity of aluminum foam in the sandwich was 55%. The multi-level optimization method was used to optimize the layering of the CFRP panels. Free size optimization was used to obtain the layered shape of CFRP under four classical ply angles, during which the mass of the panel was reduced while its stiffness improved. Based on the regularization of the CFRP layer, the ply thickness was discretized into manufacturing thickness by size optimization. Simultaneously, the number of layers of the panel was determined, and its mass was further reduced as the stiffness of the composite material is also dependent on the ply angle. Therefore, the arrangement order of the classical ply angle was obtained by ply stacking sequence optimization, further improving the panel stiffness. The results show that compared with the steel control arm, the mass of the optimized sandwich structure control arm was reduced by 26%. Simultaneously, the maximum stress at the foam aluminum sandwich was reduced from 225.6 MPa before optimization to 151.2 MPa. The safety factor and the failure coefficient of the CFRP panel after optimization were 1.1 and 0.81, respectively, both meeting the strength requirements. From the stiffness perspective, the longitudinal stiffness of the optimized control arm increased by 54.7% compared to the initial control arm of the sandwich structure, 103.2% compared to the steel control arm, and the lateral stiffness increased by 37% compared to the initial control arm of the sandwich structure and 56% compared to the steel control arm, respectively. Thus, the stiffness improvement effect was obvious. The first-order modal frequency of the optimized control arm was 785 Hz, 573.1 Hz higher than that of the steel control arm, and the vibration performance was significantly improved.