THERMOELASTIC CONSTITUTIVE MODELING OF IRRADIATED POLYMER COMPOSITES WITH MATRIX PROPERTY CHANGE AND FIBER MATRIX DEBONDING/

In this paper, thermoelastic models are presented for the evaluation o f the constitutive response of irradiated fiber-reinforced polymer com posites with change in the fiber and matrix properties and fiber/matri x interfacial debonding. These models are based upon thermodynamic con siderations involving Helmholtz and Gibbs free energies and micromecha nical stress and strain fields associated with the fiber and matrix ma terials, The proposed union between the energy functions and micromech anics provides a unifying framework that call deal with the potential property changes in the fibers and matrix and at the fibre/matrix inte rface. The results for a typical graphite/epoxy polymer composite syst em show reasonable trends when compared with the available experimenta l data for primary elastic constants. Tile parametric study for all th e principal elastic constants involving matrix stiffening, softening a nd fiber/matrix interfacial debonding exhibit a number of interesting results. A significant influence of interfacial fiber/matrix debonding on the matrix-dominated material properties, such as (E(2))(c)(r) and (G(66))(c)(r), has also been noted.