An intrinsic investigation of surface treated Kevlar intraply patch-repaired glass fiber polymer composites

Fiber-reinforced polymer composites have attracted considerable interest from the aerospace industry to repair existing engineering structures. This is mainly because such composites are more affordable than replacements. This study reveals that glass/epoxy parent composite laminates were repaired using a Kevlar/glass intraply hybrid patch with various volume fractions, such as 44/56 (% by vol) and 64/36 (% by vol). Moreover, the 15% phosphoric acid (PA)-pretreated 1-h epichlorohydrin (ECH)-treated Kevlar fibers were used for glass intraply patch hybridizations. EDAX and XPS analyses were used to observe the chemical components and bonds activated in the surface-modified Kevlar fiber surface. The quasi-static indentation (QSI) of chemically treated Kevlar hybrid patch-repaired composites was investigated and compared to virgin and untreated Kevlar hybrid patch composites. The results showed that the treated Kevlar hybrid patches achieved a desired level of stiffness and strength, in comparison to the untreated and original repair composites. The ultimate load of the Kevlar surface-treated patch composites increased by 27.36% and 41.1% compared with the untreated Kevlar hybrid patch-repaired and unrepaired glass/epoxy parent laminates, respectively. Furthermore, the stiffness of the treated Kevlar hybrid patch-repaired sample increased by 38.4% compared to untreated Kevlar hybrid patch samples. The indentation damage failure analysis of the repaired composite laminates was investigated by acoustic emission (AE) analysis. It was revealed that the delamination and fiber breakage AE hits percentage of treated Kevlar patch were decreased by 22.1% and 31.1%, respectively, compared to the untreated Kevlar patch-repaired samples. Also, the indentation damage behaviors were analyzed and validated by scanning electron microscopy (SEM).