On the Failure Work and Modulus of Composites Reinforced by Thin Elastomer-Coated Fibers

Abstract

Fiber reinforced composites have high specific strength, excellent fatigue resistance and variable directional freedom in property control, allowing for optimal structural design. A deficiency in stiff fiber reinforced composites is poor low-speed im pact resistance (i.e., low energy absorption before major failure). This has been ex perimentally shown to be remediable by coating the reinforcing fibers with an elastomeric coating. However, the stiffness of the composites is decreased because of reduced effi ciency in interface load transfer in the soft coating. This can be improved by making the coating very thin. For practical design, it is necessary therefore to provide an analytical relation between the increase in failure work and the corresponding decrease in stiffness with the coating properties. Interface stress concentration is parametrically studied in this paper. A formula for calculating the longitudinal modulus of composites reinforced by aligned coated fibers is proposed. The formula is based on a combination of both compos ite mechanics and finite-element stress analysis. The results provide fundamental guide lines to practical engineering applications of composites of elastomer-coated fibers.

Keywords

rubber coating rubber-coated fibers graphite fiber composites glass fiber composite impact strength energy absorption longitudinal modulus stress concentration.

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