THE EFFECT OF FIBER MISALIGNMENT ONPARAMETER DETERMINATION USING PICTUREFRAME TEST

摘要

In this paper, a hyperelastic model is used to investigate the effect of possible fiber misalignmentduring constitutive parameter identification using the picture frame test. The model utilizes aphenomenological invariant-based approach, in which no assumption is made concerning fiberextensibility. The test kinematics are first developed in full generality based on twotransformations: the trellis and the enlargement, corresponding to the shear and fiber-stretchmodes, respectively. Subsequently, a set of test data from bias extension, picture frame, anduniaxial extension experiments on twill 2x2 fabric is employed to identify the model parameters.In doing so, the effect of fiber misalignment is first neglected. Then, arbitrary fiber misalignmentis included within the identification process, such that the stretch in the fiber directions isaccounted for. Eventually, by comparison of these two, the effect of fiber misalignment onparameter determination using the picture frame test is concluded.