The use of rigid polymeric foams has been well-established to result in asignificant improvement in the energy absorption and safety of the vehicles, owing tothe excellent energy absorption characteristics of these materials. As an optimumenergy-absorbing material system, polymeric foams need to dissipate the kineticenergy of the impact, while maintaining the impact force transferred to the protectedobject at a low level. Therefore, it is crucial to accurately characterize the load bearingand energy dissipation performance of foams at high strain rate loading conditions.However, there are challenges render to accurately measure the deformation responseof foams due to their low mechanical impedance properties. Recently a nonparametricmethod was proposed and successfully implemented to enable the accuratemeasurement of the compressive constitutive response of rigid polymeric foamssubjected to impact loading conditions. The method is based on stereovision highspeed photography in conjunction with 3D digital image correlation and allows foraccurate evaluation of inertia stresses developed within the specimen duringdeformation time. The inertia stresses are then superimposed with the boundarymeasured impact force to facilitate the measurement of full-field stresses in thespecimen. Full-field distributions of stress, strain and strain rate are then used toextract the local constitutive response of the material at any given location along thespecimen length. Accordingly, the local energy absorption curves are extracted andthen averaged to give the effective energy absorption response of the examined foam.Finally, results obtained from the proposed non-parametric analysis are compared withthe data obtained from the conventional test procedures.
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