The internal strain distribution in an injection-molded plate of crystalline thermoplastics, polyphenylene sulfide (PPS), reinforced with 40 mass % of glass short fibers was measured by the diffraction method using synchrotron X-rays with an energy of 20.0 keV. The injection molded plate has roughly three-layer structure where the fiber orientation is parallel to the molding direction in the shell layer and is nearly perpendicular in the core layer. The strain scanning technique was successfully applied to measure the change of in-thickness distribution of strain in PPS matrix under uniaxial tensile loading both in the molding and transverse directions. The change of PPS strain in the loading direction is roughly identical to the applied macrostrain; strictly speaking, it is larger in the direction perpendicular to fibers than that parallel to fibers. The PPS strain in the thickness direction decreased with increasing applied strain. The rate of the change of PPS strain with the applied strain measured by X-rays is smaller than that predicted by the micromechanics of composites with aligned short fibers. The influence of three-layer structure on PPS strain in injection-molded plates subjected to tensile loading was successfully predicted by the finite element analysis combined with micromechanics.
