Design, development and analysis of a full carbon fibre reinforced composite chassis of an electric vehicle
Khoo, Raymond Rui Xiang
Date of Issue2015
School of Mechanical and Aerospace Engineering
Design for steel vehicle structures is a well-researched topic and has many research publications covering important aspects and factors that affects the design of a vehicle structure including manufacturing techniques and limitations. However published literature for developing carbon fibre composite vehicle structure are very limited, many focus only in sub-components carbon composite implementation without considering overall structural requirements and application. Many considerations used in steel vehicle structures are not valid with the use of carbon fibre composite due to the differences in material mechanical property especially in the area of crashworthiness. New design considerations have to be devised for developing carbon composite vehicle structures. The EVA electric taxi project provided the foundation to achieve that. The EVA project aims to develop an efficient, fully functional, prototype electric vehicle for tropical megacities and will feature a full carbon fibre composite structure to reduce overall weight and prototyping cost. Listed below was the responsibility of the author in EVA project. • In-charge of vehicle crashworthiness development • Providing crash load requirements to all sub-system design • Carbon composite material property testing • Conduct FEA analysis of the vehicle structure • Define layup for the whole vehicle structure consisting of 68 composites panels • Develop design solutions for weakness in vehicle structure • Design of aluminium crash structure • Experimental verification of aluminium crash structure • Oversees the body in white structure overall assembly and tolerance. • Assembly of EVA A comprehensive literature review of vehicle crash standards and crashworthiness design along with vehicle structure performance requirements was carried out to understand the design criteria of vehicle structures. These are further complimented by review of material mechanical properties, property degradation under failure and how to simulate these failures in Finite Element Analysis (FEA). The advantages, limitations and complexity to perform such simulations will be evaluated to formulate a realistic achievable vehicle structure development targets and steps in this report. Methods to simplify complex dynamic load problems into equivalent quasi-static load will also be explored to speed up development process. The multi-disciplinary nature of the vehicle project would requires multiple systems integration resulting in strict design space restrictions within the vehicle package in which key factors that affect efficient vehicle structure performance for crashworthiness will be identified. Furthermore a brief design methodology to work around these restrictions will be explored. Results of the development along side with findings and observations will be documented in the later section of the thesis showing how goals and objectives of a lightweight crashworthy prototype vehicle structure were achieved. The final weight of composite vehicle structure came in at 220kg at the end of the development which is 100-150kg lighter than comparable steel vehicle structure in this vehicle size and class. Subsequently EVA electric taxi concept was officially presented at Tokyo Motor Show in late November 2013.
DRNTU::Engineering::Mechanical engineering::Motor vehicles