Abstract

The in situ shear response of the matrix in polymer matrix composites (PMC) has been studied. Torsion tests were performed on solid cylinders of unidirectional glass fiber reinforced/vinylester and unidirectional carbon fiber reinforced/vinylester composites. The composite specimens were subjected to a uniform rate of twist. From the composite stress-strain curve, a plot of tangent shear modulus vs shear strain was derived. Then, using the Halpin-Tsai equations, the in situ matrix shear modulus was determined. The in situ matrix properties obtained from glass/vinylester and carbon/vinylester composites were found to be different. In addition, the properties of the in situ matrix were found to be a function of fiber volume fraction and the elastic properties of the reinforcing fiber. The behavior of the in situ matrix as a function of the fiber volume fraction was explained by using a three cylinder interphase model. The validity of the interphase model in predicting the composite shear modulus was studied by comparison of results against a conventional 2 cylinder model.

Issue Section:
Technical Papers
Keywords:
carbon fibre reinforced plastics, glass fibre reinforced plastics, shear modulus, torsion, stress-strain relations, shear deformation, composite material interfaces
Topics:
Carbon, Composite materials, Fibers, Glass, Shear (Mechanics), Shear modulus, Cylinders, Polymer composites, Stress-strain curves, Torsion, Shear stress
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