Design of roof panel with required bending stiffness using CFRP laminates

Abstract

Carbon-fiber-reinforced plastic (CFRP), which is strong and lightweight, is used in fabricating composites for a number of applications such as aircraft, transportation, and machinery. Automotive roof panels composed of CFRP require high strength and bending stiffness to ensure driver safety during rollover. Generally, the mechanical properties of CFRP products depend on the layup method. Therefore, this study aimed to design an automotive roof panel using CFRP laminates that would satisfy the bending stiffness requirements. Finite element (FE) analysis was used to predict the bending stiffness of automotive roof panels manufactured using CFRP laminates and thereby reduce the production time and cost. First, the CFRP laminate thickness necessary to achieve the required bending stiffness of 20 N/mm was determined. Automotive roof panels of four different thicknesses — 1.4, 1.6, 1.8, and 2.0 mm — were modeled and evaluated by FE analysis, and the 2.0-mm-thick panel was found to achieve the required bending stiffness. FE analysis was also used to evaluate the abilities of eight different lay-up methods to enhance the bending stiffness of automotive roof panels. Finally, CFRP roof panels fabricated using two different lay-up methods were evaluated by bending tests performed under the same conditions as those used in the FE analysis.