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Observation of the interaction between transverse cracking and fibre breaks in non-crimp fabric composites subjected to cyclic bending fatigue damage mechanism

This work presents observations of fatigue damage in a quasi-unidirectional polymer reinforced composite made from basalt fibre non-crimp fabric and epoxy. Through observations over large areas, the study provides quantitative observations of the damage caused by the cyclic bending loads, with focus on the damage in the tension-tension loaded region of the specimens. The observations reveals that the fatigue damage mechanism that governs the stiffness degradation of the composite occurs only in regions subjected to tensile stresses. Damage incurred from tensile loads are governed by local interactions between transverse and longitudinal fibre bundles. It is determined that cracks in transverse bundles interact with longitudinal bundles to cause breakage of fibres. These fibre breaks are found to be the main driver for stiffness degradation of the material. Similar accounts exists in the literature based on qualitative observations. The current study provides evidence, in the form of quantifiable observations, to further strengthen the argument for considering the damage mechanism as the main cause of stiffness degradation in quasi-unidirectional non-crimp fabric composites.