Nonlinear Viscoelastic Response of Unidirectional Fiber-Reinforced Composites in Off-Axis Loading

Abstract

A three-dimensional micromechanical model based on the assumptions of simplified unit cell method (SUCM) is presented to obtain the closed-form solution for overall behavior of a unidirectional polymer matrix composite. The composite system consists of nonlinear viscoelastic matrix reinforced by transversely isotropic elastic fibers. The Schapery single integral viscoelastic constitutive equation in multiaxial stress state is used to model the nonlinear viscoelastic matrix. The presented analytical formulation is able to predict the effective response of the composite in any combination of normal and shear loading conditions. In particular, the effective creep response of the material in the off-axis loading is investigated. Prediction of the presented analytical model for the creep response of glassy amorphous polymer PMMA material shows good agreement with available experimental data. Furthermore, the predicted overall creep behavior of 10 and 908 off-axis coupons of graphite/epoxy composite demonstrate close agreement with experimental and other numerical results available in the literature. The overall creep-recovery of the graphite/epoxy composite in various off-axis loading conditions for several stress levels is also presented.

Micro-Macro Analysis of Viscoelastic Unidirectional Laminated Composite Plates Using DR Method

“…The model was extended to include the nonlinear viscoelastic material properties in closed form functions in terms of the time-dependent properties of the matrix material [18]. The RVE is subdivided into four subcells, shown in Fig.…”

“…So the final set i.e. E 1 and υ L , are computed [18]. For the shear properties of the material, the in-and out-of-plane shear stresses are applied to the RVE.…”

“…The resulting equations are substituted into constitutive relations, gives the shear stresses in term of global shear strain. Consequently, a closed-form solution for overall axial and transverse shear modulus of the composite is obtained [18]. An iterative scheme is used to correct the subcells stress and stress dependent properties of matrix.…”

“…In a recent work, using the Schapery nonlinear viscoelastic model, Haj-Ali and Muliana [17] implemented four-subcell micromechanical model of Aboudi to find the effective response of unidirectional nonlinear viscoelastic composites in an incremental form. The authors [18] obtained the effective normal and shear properties of the unidirectional composite material by SUCM. The creep strain results of 90°and 10°off-axis specimen compared well with the Aboudi's model and available offaxis experimental data.…”

Nonlinear Viscoelastic Response of Unidirectional Polymeric Laminated Composite Plates Under Bending Loads

“…Micromechanical modeling of viscoelastic composite systems has been accomplished using MOC and Schapery nonlinear viscoelastic for matrix material [6,7]. The SUCM was extended to include the nonlinear viscoelastic response of the matrix material by the authors [8]. The effective properties of the composite material were obtained in closed-form expressions in terms of fiber and matrix properties.…”