A model for the computation of the complex moduli iu the fiver direction of aligned short fiber reinforced composites is suggested in this paper. The usual model for such purpose is based on an analysis of an isolated elastic fiber embeded in the matrix.The pr went model takes into account the mutual effects of the transversely neighboring fibers and of the longitudinally adjacent fibers.The packing georr.etry of fiber is shown in Fig. 1. By solving the basic equations (4)-(6) under conditions (1)-(7),the stresses in the fiber and in the gap (filled with matrix) between the adjacent fibers can be determined. It can be shown that the average of the stress in an fiber (or in a gap) and the stress in any one of neighbors does not change with x.This average can then be used as the macroscopic Stress of fiber to calculate the elastic modulus of the composite .According to the correspondence priniple of viscoelasticity by replacing the elastic moduli of the fiber and the matrix by complex ones the above procedure will give the complex modulus of the compo site Feig,2 shows another packing geometry which is more close to that of test specimens made with prepregs. The. numerical results are depicted in Figs. 3-7,from which the following conclusions can be drawn 1)The storage modulus E
ć decreases and the loss modulusE
ć increases rapidly with the gap size when the gap size is about or less than the size of fiber cross-section.The variations become slow when the gap size exceeds that range. 2) Aa shown in Fig. 6,when the fiber is long the gap size has no significant effect on the moduli.This means that the breakage of scme fibers in a continuous fiber reinforced composite has very little effect on the stiffness of the composite if the breakages do not occur on the sane crosssection. 3) The curves 4 in Fig.7 show that the packing geometry in Fig.2 gives an appreciably better agreement with experimental resuits.It proves the present model is an improvement upon the existing ones represented by the curves 1 and 2.
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