Effects of interphases on the mechanical, thermal and hygromechanical response of fiber-reinforced composites
The effects of fiber-matrix interphases on the micro- and macro-mechanical properties of unidirectionally fiber-reinforced composites have been studied for composites subjected to transverse uniaxial, biaxial and shear loadings, uniform temperature changes and uniform changes of moisture concentration. The interphases have been modeled by the spring-layer model which accounts for continuity of tractions, but allows radial and circumferential displacement jumps across the interphase that are linearly related to the normal and tangential tractions. Numerical calculations in basic cells have been carried out using the boundary element method. For the isothermal case the results display the effects of variation of interphase stiffness on the fields of stress and deformation and on the effective elastic constants for square array, 45 deg rotated square array and hexagonal array composites with and without interphase failure and radial matrix cracking. For a hexagonal array, under the assumption that the failure mechanisms follow the periodicity of the composite, the stress intensity factors at the tip of L-shaped and perpendicular-shaped matrix cracks and the reduction of the effective elastic moduli due to the matrix cracks and interphase damage have been calculated and the conditions for matrix crack propagation and extension of interphase damage have been analyzed. A fiber with a reduced interphase stiffness contained in a unidirectionally fiber reinforced composite gives rise to higher stresses at its interphase as well as at the interphases of neighboring fibers. For a hexagonal array composite, detailed numerical results are presented. Three cases have been investigated: (1) a perfect composite, (2) a perfect composite which contains a single fiber with a lower interphase stiffness, (3) a perfect composite which contains a single fiber with interphase cracks and a lower interphase stiffness.
- Research Organization:
- Northwestern Univ., Evanston, IL (United States)
- OSTI ID:
- 7267828
- Country of Publication:
- United States
- Language:
- English
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