Mechanical Property Predictions for Short Fiber/Brittle Matrix Composites

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Abstract
A model is presented which predicts the effects of fiber orientation and matrix microcracking on the monotonic tensile stress-strain curves of composites with short fibers and brittle matrices. A hypothetical composite with aligned fibers is modeled as having elastic constants which decrease with strain in monotonic loading. These properties are measured for a composite with continuous aligned glass fibers in an un saturated polyester matrix by testing various laminates. The results successfully predict the nonlinear stress-strain curves of other lamination sequences. A short fiber com posite with identical composition is fabricated into samples with different fiber orienta tion distributions. The fiber orientation states are characterized using radiographic tracer fibers. The properties of these composites are successfully predicted, though the effects of microcracking are somewhat different, showing a degradation in longitudinal modulus due to fiber end cracks and a more stable transverse modulus due to crack arresting.