Measurement of fiber orientation distribution in injection-molded short-glass-fiber composites using X-ray computed tomography

Abstract

Being able to measure the fiber orientation distribution in the injection-molded composite parts is of considerable importance, since the distribution locally affects the mechanical and physical properties of the final part such as its strength, impact toughness, internal stress, and fatigue properties. In this study, we experimentally measured the fiber orientations in two injection-molded specimens produced from 30wt% short-glass-fiber-reinforced polyamide 6 using plate-shaped cavities with and without a weld-line. The fiber orientation distributions were observed directly using a high-resolution three-dimensional (3D) X-ray computed tomography (CT) system XVA-160α. A simple method based on a series of X-ray CT images was developed to measure the orientation angles of the individual fibers. Further, precise 3D calculations of the fiber orientations related to the second-order orientation tensor components were performed to obtain a consistent description of the observed behavior. Consequently, this study explored a potential application of X-ray CT imaging, a novel and powerful technique for observing and measuring fiber orientation. Further, the software CIMP-PACK3DM was employed to analyze the resin flow in the mold cavity using the finite element method (FEM). The filling patterns of the injection-molded plates with and without a weld-line as determined using FEM were in good quantitative agreement with the X-ray CT imaging analysis results. It was found that the fiber 3D orientation distributions of the injection-molded plates with and without a weld-line could be obtained with precision by combining the high-resolution 3D X-ray CT system XVA-160α with the resin flow analysis software CIMP-PACK3DM using FEM.