Anisotropic visco-elastic properties identification of a natural biodegradable ALFA fiber composite

Abstract

In order to design parts or mechanical structures made up of heterogeneous materials, composed from a polymer matrix and a natural biodegradable fiber like the ALFA, material properties of such a composite have to be known. The purpose of the present study is to propose a method for identifying the visco-elastic properties of an ALFA/PMMA composite. Unidirectional and woven composites made of the ecological ALFA fiber are studied. The properties of the ALFA fiber were determined via multiple physical tests the results of which were processed with the Weibull distribution law. Given the relaxation law of the matrix and the properties of the natural ALFA fiber, the method determines the relaxation law of the homogenized composite. To achieve that, a representative cell is chosen and then subjected to unitary displacement numerical relaxation tests. The numerical tests results are used in a non-regression identification algorithm in order to find, as a mathematical reusable form, the composite visco-elastic Prony series of the stiffness matrix components. From the stiffness matrix, using a direct and an inverse Fourier transformation, the compliance matrix is computed and the orthotropic engineering property expressions are identified. The obtained results are compared to an ultrasonic measurement test of an ALFA/PMMA 45% specimen.