Anisotropic tensile behaviour of short glass-fibre reinforced polyamide-6

Abstract

This paper presents an experimental investigation of injection-moulded short glass-fibre reinforced polyamide-6 reinforced with 0 wt.%, 15 wt.% and 30 wt.% fibres. The fibre orientation distributions are characterized by use of X-ray computed tomography. A shell-core-shell structure is found through the thickness of the materials, where the predominant fibre orientation is along the mould flow direction (MFD) in the shell layers and perpendicular to the MFD in the core layer. To study the mechanical behaviour, uniaxial tensile tests are conducted in seven directions relative to the MFD. The tests are instrumented with two cameras, which allows for accurate measurement of all strain components. The fibre-reinforced materials show moderate to high degree of anisotropy, increasing with the fibre content. Young’s modulus, in-plane and out-of-plane Poisson’s ratio, stress at maximum force and fracture strain vary smoothly with the in-plane specimen angle. It is demonstrated that orthotropic elasticity is an excellent approximation for the anisotropic elastic behaviour of the fibre-reinforced materials.