マイクロメカニックスによる短繊維複合材料の力学的挙動の解析 : 第 3 報繊維端き裂が剛性低下に及ぼす影響

抄録

Microcracks at tips of longer fibers aligned in the straining direction are more likely to form in a short-fiber composite. An analytical model for a composite is developed to estimate effects of such fiber-end cracks on stiffness reduction by applying the Eshelby's equivalent inclusion method to two kinds of inhomogeneities, i.e., crack and fiber. Additionally a frequency distribution of fiber-end stress at crack occurrence is obtained from in-situ tensile test in SEM using injection-molded specimens, and used in the analytical model. Good agreement between the theoretical results based on the present model and the experimental ones is shown about a nonlinear stress-strain relationship of carbon-fiber/polycarbonate composite. Furthermore the effects of crack radius, fiber volume fraction, fiber orientation distribution and fiber aspect ratio on crack occurrence and the stiffness reduction are investigated.