Analytical modeling of fiber-matrix interface failure in unidirectional laminae subjected to in-plane shear loads

Unidirectional laminae subjected to in-plane shear loads present complex behavior with strong nonlinear response. A novel analytical model is proposed considering a unit cell with square symmetry and circular fiber cross-section taking into account the failure on the interface between fiber and matrix. The interface failure is a shear-driven phenomenon described by a constant value during the failure process. The model validation is performed using two different approaches: the analytical estimations are compared with experimental data, and finite-element simulations are employed to evaluate the influence of fiber volume fraction. The proposed analytical model captures the main features of experimental data showing its capability and reliability to represent the complex interface debonding propagation phenomenon. Numerical simulations show in-plane shear stress-strain curves for four distinct unidirectional laminae with different fiber volume fractions. Results attest the model capability to describe composite materials with composite failure, essentially characterized by the interface behavior.