A Comparison of Transverse Properties of 50% Short and Long Glass Fiber Reinforced Nylon 6/6 Resin

Abstract

The mechanical properties of glass fiber reinforced thermoplastics are affected by fiber length and orientation within the skin and core regions that are developed during the injection molding process. Since glass fibers orient and align themselves in the direction of flow the mechanical properties of fiber reinforced materials tend to be greater in the flow direction as compared to the transverse direction. In this paper, the tensile modulus and strength of 50% long and short Glass Fiber Reinforced (GFR) nylon 6/6 machined specimens are compared in the flow and transverse direction in order to increase the understanding of transverse mechanical properties. Both materials were molded at varying wall thicknesses to investigate tensile properties as a function of part thickness. Micrographs showing the skin/core regions within the various machined tensile specimens are also presented. In general, the 50% long GFR nylon 6/6 materials yielded a higher modulus and strength in the transverse direction compared to the short GFR nylon 6/6 resin. The long GFR nylon 6/6 resin also exhibited comparable tensile properties in the flow and transverse direction at wall thicknesses of 3.2 and 4.4 mm (0.125 and 0.175 in). The greater core region in the long GFR nylon 6/6 material at the thinner wall thicknesses results in higher retention of tensile properties in the transverse direction, as compared to the short GFR nylon 6/6 material. The study shows that the long GFR nylon 6/6 resins offer significant material and performance advantages in demanding structural applications, which will be subjected to biaxial stress conditions.