The aim of this study was to find the correlation between failure modes and acoustic emission (AE) events in a comprehensive range of thin-ply pseudo-ductile hybrid composite laminates when loaded under uniaxial tension. The investigated hybrid laminates were Unidirectional (UD), Quasi-Isotropic (QI) and open-hole QI configurations composed of S-glass and several thin carbon prepregs. The laminates exhibited stress-strain responses that follow the elastic-yielding-hardening pattern commonly observed in ductile metals. The laminates experienced different sizes of gradual failure modes of carbon ply fragmentation and dispersed delamination. To analyze the correlation between these failure modes and AE signals, a multivariable clustering method was employed using Gaussian mixture model. The clustering results and visual observations were used to determine two AE clusters, corresponding to fragmentation and delamination modes, with high amplitude, energy, and duration signals linked to fragmentation. In contrast to the common belief, there was no correlation between the high frequency signals and the carbon fibre fragmentation. The multivariable AE analysis was able to identify fibre fracture and delamination and their sequence. However, the quantitative assessment of these failure modes was influenced by the nature of failure that depends on various factors, such as stacking sequence, material properties, energy release rate, and geometry.@en

In this study, the fatigue properties of carbon fiber-reinforced polymer (CFRP) composite laminates were investigated, specifically focusing on the incorporation of 100-µm polysulfone (PSU) nanofibers as an interleaving material. The PSU nanofibers were produced using the electrospinning technique. Both quasi-static and fatigue tests were conducted on both the reference specimens and the modified specimens to evaluate their mode-I performance. The results revealed an 85% increase in fracture toughness (G_IC) under quasi-static testing. The fatigue plots revealed a noteworthy reduction in the fatigue crack growth rate (da/dN) for the modified specimens due to new toughening mechanisms. Scanning electron microscopy (SEM) demonstrated that, the PSU nanofiber became melted and distributed in the interface, leading to phase separation and a sea-island structure. The presence of PSU microspheres caused crack deflection during delamination, which resulted in increased fracture and fatigue resistance.

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