Measurment and numerical simulation of three dimensional fiber orientation states in injection-molded short-fiber-reinforced plastics

To determine three-dimensional fiber orientation states in injection-molded short-fiber composites, a confocal laser scanning microscope (CLSM) is used. Since the CLSM optically sections the specimen, more than two images of the cross sections on and below the surface of the composite can be obtained. Three-dimensional fiber orientation states can be determined by using geometric parameters of fiber images obtained from two parallel cross sections. For experiments, carbon-fiber-reinforced polystyrene is examined by the CLSM and geometric parameters of fibers on each cross-sectional plane are measured by an image analysis. In order to describe fiber orientation states compactly, orientation tensors are determined at different positions of the prepared specimen. Three-dimensional orientation states are obtained without any difficulty by determining the out-of-plane angles utilizing fiber images on two parallel planes acquired by the CLSM. Orientation states are different at different positions and show the shell-core structure along the thickness of the specimen. Fiber orientation tensors are predicted by a numerical analysis and the numerically predicted orientation states show good agreement with measured ones. However, some differences are found at the end of cavity. They may result from the fountain flow effects, which are not considered in the numerical analysis. (C) 2003 Wiley Periodicals, Inc.