Optimal fiber distribution for tensile properties of injection molded composite

Abstract

The survival rate of a composite is the residual fiber length divided by the initial fiber length, and it decreases with the initial fiber length and fiber volume content (V_f) during injection molding processes. The degree of damage is higher for carbon fiber than for glass fiber, and the survival rate increases with a hyperbolic tangent relationship as the nozzle diameter increases. Higher survival rate corresponds to a stronger material. Five different lengths of fiber with 29 different size fibers were selected based on the distribution and shape of residual fiber in experimental works. These were examined to study the effects of fiber distribution on the tensile properties of a short-fiber reinforced composite (SFRC). Compared with the experimental results, the modulus predicted using the Halpin-Tsai relation shows reasonable agreement with the prediction obtained using the residual fiber length instead of the initial fiber length. It was found that the tensile modulus and strength generally differ by a factor of up to 3.2, depending on the fiber distribution patterns with V_f = 30%, and the trend is more significant as the fiber aspect ratio increases. The interactions between the fiber and matrix and the staggered-type distribution are the most important factors in the reinforcement of the SFRC. With the same combination of short fiber length, an optimized fiber distribution pattern is suggested.

Keywords:

• fiber aspect ratio
• damage during injection molding
• fiber distribution
• tensile strength and modulus
• prediction