Convertible Car Hoods - the Problem of Form-finding and Related Aero-structure Problems

摘要

A computational methodology for predicting load-displacement response of tension fabric structures, such as used in convertible car hoods, is presented. It is found that elastic material properties, such as the values of Young's moduli do not have a very pronounced effect on the behaviour of the hood membrane. The results indicate that, from the point of view of achieving a uniform tension field, (which reduces fatigue of fibres), a preferable alignment of the hood fabric should be for the warp direction running along the longitudinal axis of the car. Uncertainties associated with material properties and initial tension levels in the hood fabric all require a margin of safety. The results obtained so far indicate that this margin is rather large with regard to stresses generated in the hood fabric, but there are other important aspects that need careful evaluation, such as creep and environmental degradation of the fabric. Future development work must address these issues, together with biaxial material properties entering the formulation of the computational model.