Abstract
This paper presents the optimal structural design of the composite chassis of a high energy efficient quadricycle. The chassis consists of three main parts, realised by means of sandwich structures. The bottom frame, has an expanded polypropylene (EPP) foam core and carbon fiber-reinforced plastic (CFRP) external skins. Aramid honeycomb and CFRP skins are used for the sandwich structures of the body and the bulkhead that separates driver’s compartment and energy compartment. An optimization procedure, suitable for laminated composite structures, is employed to determine the optimal stacking sequence, i.e. shape, number and orientation of each ply. The sum of the weighted compliance evaluated for several load cases is set as objective function to minimize. Optimization constraints are related to the limit mass and to structural stiffness, strength and manufacturing aspects. The optimization procedure relies on three phases. Free-size phase aims to determine the optimum shape and continuous thickness distribution for each ply. The second phase involves a discrete optimization procedure, to determine the optimal number of plies. Finally, the optimal stacking sequence of the laminates is defined in order to meet manufacturability requirements. Compared with the non-optimized design of the chassis, the optimization approach adopted leads to a chassis featuring lower mass, with same compliance. Strength and stiffness related properties are also improved.
