Evaluation of wall thickness effect on tensile properties of injected short fiber reinforced polymers

Abstract

The aim of this paper is to analyze the effect of increasing the wall thickness in injection molded short fiber reinforced polymer (SFRP) parts, focusing mainly on tensile strain and tensile strength, as these are the most used characteristics for structural analyses. The phenomena that makes this evaluation of interest has to do with the microstructure of SFRP injection molded parts and how the fibers get oriented along the flow direction at superficial depths with an increasingly less aligned structure down to the mid plane/surface. By increasing the injected part wall thickness the ratio between the thicknesses of highly oriented layers and poorly oriented layers decreases, thus the tensile properties of the material should suffer a decrease as well.In order to study the mentioned hypothesis two types of materials were tested, PPA GF33 and PPS GF40, dog-bone type specimens were cut at different angles to the flow direction from injection molded plates of 2 and 3 mm wall thickness values. The tensile strains were recoded using a video extensometer and material data was calibrated using Digimat MX reverse engineering module and Ansys properties homogenization tool and finite element solver.