Finite Element Analysis and Experimental Investigation of the Mechanical Performance of a Full-Body Composite Monocoque Chassis for a Racecar

The conceptual design of a full-body composite monocoque chassis has been presented at various student-level racing contests due to its high strength-to-weight ratio and torsional stiffness. However experimental studies to demonstrate the performance of the design are limited. This study aims to find the optimum configuration and number of stacked layers of carbon fiber sandwich panel using finite element analysis (FEA), as well as investigate the mechanical performance of the proposed sandwich configuration by experimentation in order to demonstrate the practical performance of a fully composite monocoque chassis made from the optimized configuration of the sandwich panel. A composite monocoque consisting of five stacked layers of [W₄₅/UD₀/W₉₀/UD₄₅/W₀/core]_symmetry was proposed, where W, UD, and the subscripts indicate woven and unidirectional (UD) carbon fibers and their orientation in the measurement unit of degrees. Three-point bending and perimeter shear tests were conducted on samples of the proposed configuration. The samples exhibited a high flexural rigidity of 2980 Nm² and a small deformation of 0.99 mm in the perimeter shear test. The maximum deformation from the side impact and impact to the front bulkhead was less than 2.5 mm, which is 10 times less than the maximum allowable deformation specified by Formula SAE (FSAE) rules. A high stress of 25 MPa was generated by the applied load in both tests, but this substantially decreased throughout the chassis, indicating that the stress was mitigated and, consequently, cockpit safety was enhanced. A total weight of 29 kg and torsional stiffness of 3806.23 Nm/deg were achieved. Therefore, our suggested carbon fiber sandwich panel configuration could be implemented, with a high specific modulus and relatively high torsional stiffness, in small-scale racecars or lightweight structures.