Development of Carbon/Epoxy StructuralComponents for a Topless High Performance Vehicle

摘要

A great disadvantage associated with convertible vehicles is the loss in torsional andrnbending stiffness due to the absence of the roof structure, which completes thernpassenger compartment and forms a closed section, and the associated loss in vehiclernperformance and crash resistance. While these considerations apply to every toplessrncar, they are particularly evident in the case of high performance vehicles, as in therncase of the new Murciélago Roadster. In the earlier stages of development,rnpreliminary torsional tests indicated a 50% loss in rigidity, and it greatly reflected onrnthe handling characteristics, noise and vibration, and crash performance.rnA re-design and improvement process is implemented by introducing new structuralrnmembers or reinforcing existing ones. Among the former, an all carbon/epoxyrncomposite tubular sub-frame, first of its kind for a high performance productionrnvehicle, whose engineering from preliminary design to manufacturing is hererndiscussed. Such structure is comprised of tubular tension and compression members,rnwhich can retain the full benefit of the mechanical properties of advanced compositernmaterials. While the original sub-frame was designed with cylindrical steel tubes, thernproduction model has been awarded to the composite one since it provided an overallrnweight saving of 44%, in spite of the nearly double manufacturing/material costs.rnFurthermore, it exhibits improved performance for higher stiffness, ease ofrntransportation during assembly, part consolidation and esthetics. Use of aerospacerngrade materials and technologies is justified for this component due to the criticalrnnature of the application and its complex geometry.rnComposite structures that already are employed in the Murciélago Coupe [1,2] havernbeen enhanced with selective or global reinforcements, and they include the doorsillrnelements, the rocker panels, and the floor pans, which altogether greatly increase therncompartment's rigidity and crash resistance. Furthermore, the extended structuralrntunnel, which connects the front to rear firewalls, acts as effective load path andrntransfers the kinetic energy at impact to the massive rear structure of the vehicle.