j soc mater sci jpn

Abstract

Three kinds of theoretical methods based on (a) an extended empirical formula with a contiguity factor, (b) an approximate averaging method and (c) a finite element method, were proposed to predict the elastic constants of high performance carbon fiber reinforced plastics taking account of the anisotropy of carbon fiber itself. The fibers were assumed to be distributed in hexagonal or square arrays in the analyses (b) and (c).Experiments by three kinds of loading, that is, axial tension, circumferential tension and torsion, were carried out to measure the anisotropic elastic constants of two kinds of filament-wound cylindrical specimens reinforced by two different carbon fibers. Through these experiments, the anisotropy of carbon fiber was quantitatively estimated and the theoretical elastic constants based on these values agreed well with the experimental values obtained on the herically wound and laminate specimens. It can be concluded from this work that (1) the anisotropy of carbon fiber is extremely large, i. e., the transverse modulus is about one fifteenths to thirtieths longitudinal modulus, (2) the analysis assuming the square array of fibers give larger elastic rigidity than that for the hexagonal array, and (3) all of the three proposed theoretical methods give nearly the same values, so that the analytical method such as (a) or (b), which gives the solution in closed form, can be conveniently used in estimating the elastic constants of composites with arbitrary composition and in evaluating the quantitative effect of elastic characteristics of the constituent materials on them.