Pseudo elastic methods for damage assessment of composite tubes

Abstract

Rapid urbanization globally has led to increased traffic congestion within cities which often result in low speed collisions. These low speed collisions can happen during parking of Vehicles also. Bumpers provided for the Vehicles primarily absorb the impact energy during these low speed collisions. However, a portion of this, impact could get transferred to the thin walled tubular structures attached to the bumpers whose main purpose is to effectively absorb the Impact energy and compliment occupant safety, in the event of an accident. These structures are usually provided with notches of specific sizes at select locations to improve crush (energy absorption) efficiency and result in uniform crushing pattern. These notches could experience localized damage during low speed collisions. Such a scenario could make the crush tubes ineffectual as energy absorbers, after few such collision cycles due to localized partial damage. Hence it is desirable to check the design for possibility of localized damage during low speed collisions. Computation of damage requires prediction of notch energy or associated strains. Usage of Finite Element methods for damage evolution prediction of composite elements poses several challenges, especially for anisotropic materials like Composites. Several approximate methods have been proposed and are being used for evaluation of Elasto-Plastic strains, for isotropic materials. The adaptability and relative accuracies of these methods namely The ESED rule, arc Length Method and Neuber’s rule under axial compressive loads for anisotropic composite materials have been investigated and presented.