EVALUATION OF CREEP COMPLIANCE OF CARBON-FIBER-REINFORCED COMPOSITES BY HOMOGENIZATION THEORY

Effective creep compliance of carbon-fiber-reinforced composites is ev aluated for applications of composites at elevated temperatures. A hom ogenization theory with two-scale asymptotic expansion in the Laplace domain is used to solve viscoelastic problems of composites. Effective constitutive equations and microscopic disturbed displacements are de rived from the homogenization theory. A hexagonal array of fibers is e mployed for the microstructure of the composite and a hexagonal unit c ell is placed in the microscopic field to represent a boundary value p roblem. In numerical calculations, a carbon-fiber-reinforced composite with thermoplastic matrix is considered at the glass transition tempe rature of the matrix. The matrix is viscoelastic and is represented us ing the generalized Maxwell model at the glass transition temperature, and fibers are considered as a transversely isotropic elastic medium. The effective creep compliance of the composite is determined by nume rically solving a set of equations for macro-and microscopic fields.