Investigation of Relaxation Properties and Potentiality of the Thermoformability of HDPE Charged by Wood Flours

The processability of the composites made up of wood and a matrix of thermoplastic materials was experimentally and numerically investigated for six different proportions of wood flours. To take account of the enclosed gas volume responsible for inflation of the thermoplastic composite membrane, which contributes significantly to the strength and stiffness of a thermoplastic composite structure, we considered a thermodynamical approach to express external work in terms of a closed volume. The pressure load is thus deduced from the thermodynamic law of the Redlich-K wong real gas. The viscoelastic behavior of the Lodge model is considered. The Lagrangian formulation together with the assumption of the membrane theory is used in the finite element implementation. Moreover, the air flow influence on the inflation of bubble is analyzed for six different proportions of wood flours in the HDPE material.