Calculation of Filament Volume Fraction in Dry Roving and Constants of Parameters of Composites Made of Unidirectional Fibers

Abstract

The paper presents a method making it possible to reveal the minimum cross-sectional area, maximum volume fraction of filaments (fibers) of a roving, and minimum volume fraction of the interfilament gaps of a dry roving, which are independent parameters (constants) of roving. Each kind of roving taken separately has parameters relevant only to it (technical data). Practical application of the method is demonstrated by examples of determination of these data for rovings of carbon (CF) and ultrahigh-molecular-weight polyethylene (UHMWPE). The ratio of the cross-sectional areas of the resin-impregnated and dry roving depends on the amount of matrix within the interfilament gaps and is a constant, which is assigned by the impregnation technology. The constants of rovings are a base for calculation of the reinforcement factors for components of composite. The constants make it possible to simplify the calculation of the number of rovings at prespecified concentration of reinforcement components in hybrid composites made of unidirectional fibers. Examples of utilization of the constants for the calculation of volume, required quantity, density, and volume fractions of reinforcement components in composites made of unidirectional fibers are presented. The difference of degree between actual volume fractions of fibers in the rovings and ideal values calculated for hexagonal and tetragonal spacing of fibers is revealed too.