There have been several papers hitherto published relating to young's modulus of polymer film filled fragmented glass fibers to the moduli of its constituents. Few of them have, however, taken the orientation distribution of the glass fibers into consideration in calculating the bulk modulus.
In this paper, the effect of orietation distribution of the glass fiber upon the bulk modulus is first formulated on a basis of the homogeneous stress hypothesis for an aggregate model of concentric structural units consisting of the glass fiber surrounded by the polymer component. Then, the structural unit is corrected so that the normal stress in the fiber varies along the fiber axis.
The anisotropy of Young's modulus calculated upon the above given model agrees fairly well with that observed for polyethylene and polyester films both filled with glass fibers in a range of volume fractions less than 30%.