Design and Finite Element Analysis of a Composite Monocoque Chassis for the Shell Eco Marathon Project 2012

The presentation and paper present details of the design and development of a fully composite monocoque chassis for Coventry University's Shell Eco-Marathon vehicle, replacing the current tubular design able to do 600mpg (presented at the Altair European conference in Versailles in 2010).

It follows the design through from the initial research stage to a finalised design that could be ultimately manufactured. The vehicle aerodynamic performance was analysed using CFD analysis and was judged very promising as the drag coefficient was reduction from 0.26 to 0.1, hence reducing the aerodynamic drag force by 60% making the vehicle far more fuel-efficient. The design constraints and product design specification were used to ensure the vehicle complied with all the rules and regulations, as well as manufacturing constraints.

Early on in the project it was found that carbon fibre would be the most suitable material for the manufacture of the design. Once designing the vehicle and finalising the geometry, a CAD model produced which was was submitted to a rigorous series of finite element analysis and optimisation using HyperLamite coupled with OptiStruct.

Two approaches were taken to find the optimum design. One used a pure carbon fibre approach over the entire body of the monocoque. The other one used honeycomb sandwich panels in areas prone to bending to allow structural reinforcement and decrease the thickness of material elsewhere.

The study has concluded that the honeycomb sandwich panel reinforcements helped to produce the greatest weight reduction. The final design weighed only 13.73kg, under half the weight of the original tubular chassis, whilst combining all the aerodynamic features.

The final design was fully checked for stresses and laminate failures within the final analysis, showing that the optimised design was a viable solution for manufacture. This design now has the ability to be taken further to the manufacturing stage to provide the Coventry University Eco-Marathon team with the ability to achieve over the 1500mpg target by 2012.

The Author

Olivier Grimes
University Coventry

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