Inter-fibre failure under biaxial loads in glass–epoxy composite materials: Effect of the presence of a nearby fibre

Abstract

Fibre-reinforced composite materials are especially prone to transverse failure. It appears at the lamina level following the mechanism known as matrix/inter-fibre failure. This mechanism of damage is associated with the appearance of fibre–matrix debonds (interface cracks), as shown in previous numerical micromechanical studies. After the nucleation, growth and kinking into the matrix, these interface cracks give rise to the final macro-failure.

When compared to uniaxial loading, the growth stages of this mechanism of damage (analysed in light of Interfacial Fracture Mechanics) show some alterations under different combinations of biaxial loads. This work gives a step forward and focuses on the micromechanical BEM study of the evolution of an interface crack in the presence of a neighbouring fibre. Thus, after considering a transverse tensile load (nominally responsible for the failure) a secondary transverse load is also applied (tensile or compressive, perpendicular to the primary load). When considering the two-fibre BEM model, the results obtained lead to identifying the neighbouring fibre locations that act as accelerative agents on failure progression and establishing the effect of the biaxial load on them. Specifically, when a secondary tensile load is applied, the presence of the nearby fibre (for most of its positions) confirms the slight inhibition of the mechanism of failure for biaxial tensile loads already referred to in previous single-fibre studies by the authors. As the secondary tensile load increases, it tends to mitigate the effect of the presence of the neighbouring fibre that was previously observed for uniaxial tensile load. The opposite effects are found when a secondary compressive load is considered, which intensifies the alterations of the presence of the neighbouring fibre on the interface crack growth. Experimental evidence on some aspects is provided confirming the associated conclusions derived from the numerical models.