Experimental and Finite Element Simulation of Torsional Performance of Skin-core Carbon Fiber-reinforced Composite Rod

For decades, carbon fiber-reinforced composite rods (CFRPRs) have exhibited the advan-tages of high specific strength, high specific modulus, corrosion resistance and low den-sity, which are widely applied in the aerospace and automotive industries. In this study, a type of skin-core composite rod (SCCR) was manufactured through vacuum-assisted resin infusion technology, and the skin is a two-dimensional (2D) carbon fiber braided tube while the core is unidirectional carbon fiber. Both torsion experiment and full-size meso-scopic numerical simulation were conducted to investigate the special structure effect of SCCR. The results demonstrate that ductile failure mechanism dominates in SCCR, and the extension cracking occurs in the matrix along the direction of braiding yarn while the braiding yarns mainly experience tensile and shear damage. Under the same torsion angle, the damage degree of the resin structure (RS) and braiding structure (BS) is intensified with the braiding angle. With the increase of the braiding angle, the maximum stress of the rods increases, while the BS failure torsion angle decreases. The average stress of the mid-dle section of BS is 234.08, 239.78, and 257.93 MPa corresponding to the braiding angle of 24 degrees, 27 degrees, and 30 degrees, and the critical failure torsion angle is 209 degrees, 199 degrees, and 189 degrees. The path stress of the braiding yarn fluctuates at 5 MPa and the position of the stress fluctuation increases with the braiding angle. This study reveals the unique bearing and damage mech-anisms of skin-core composite rod, and provides the theoretical and experimental basis for the design of composite rod.