Effect of Interleaves on the Damage Mechanisms and Residual Strength of Notched Composite Laminates Subjected to Axial Fatigue Loading

Abstract

The effect of interleaving on the fatigue damage mechanisms and residual tensile strength of two graphite/epoxy material systems subjected to cyclic axial loads is investigated. The two materials, AS4/985 and AS4/1808, have stacking sequences of [0/45/90/-45]s2 and [0/-45/90/45]s4, respectively. All specimens have centrally located through-holes. The 16-ply specimens are subjected to tensile fatigue loads, while the 32-ply specimens are subjected to fully reversed fatigue loads. Interleaving these laminates at every interface with a thin (on the order of 10% of the ply thickness), tough, thermoplastic film results in an expected increase in mass and decrease in laminate stiffness, but also in higher virgin tensile strengths, lower normalized residual tensile strengths, and slightly altered damage patterns and rates of damage growth in both laminate types. The presence of the interleaves alters the baseline virgin tensile load-to-failure and damage patterns to a greater extent in the 1808 material than in the 985 material.

Experimental Investigations on Fatigue Damage and Residual Properties of Interacting Notched Woven E-Glass/Epoxy Composite

“…The stress redistribution ahead of the notch due to reduction in stress concentration increases the residual strength over unfatigued laminate [1][2][3]. The damage accumulates, propagates and finally the fracture occurs [4].…”

Numerical Approximation of Stochastic Systems for Composite Materials Based on Markov Chains

“…Recently, the numerical methods for some material models have been studied extensively [3,4]. Swain et al [5] investigated the effect of interleaves on the damage mechanisms and residual strength of notched composite laminates subjected to axial fatigue loading. Wei et al [6] used stochastic Markov chain methods to model the fatigue damage evolution in composite materials subjected to cyclic mechanical loadings and monitored by infrared thermography techniques.…”