No abstract

No abstract

In this paper, the effect of introducing different phases of fibre reinforcement in epoxy matrix at the dressed site in adhesively bonded external patch repair for damaged glass/epoxy composites under in-plane compressive loads was investigated. Three repair materials consisting of an epoxy matrix reinforced with either micro sized particulate fibres, chopped short fibres or continuous fibres were used in this study. Since this investigation extensively focuses on the effect of different types of fibre reinforcements on residual compression properties of repaired glass/epoxy composite laminates, the external patches were avoided. Acoustic Emission (AE) and Digital Image Correlation (DIC) were utilized to form qualitative and quantitative assessments of the damage progression profile. The compression results illustrate that reinforcing the epoxy adhesive material with glass fibres significantly increased the residual compression strength of repaired glass/epoxy composite specimens. In particular, the use of chopped fibre reinforced adhesive repair material improved the average residual compressive strength by 18.91 % in comparison to the specimens conventionally repaired using neat epoxy resin.

The present work is focused on improving mode I and mode II delamination resistance of glass/epoxy composite laminates (50 wt.% of glass fibers) with milled glass fibers, added in various amounts (2.5, 5, 7.5 and 10% of the epoxy weight). Including fillers in the interlayer enhances the delamination resistance by providing a bridging effect, therefore demanding additional energy to initiate the crack in the interlaminar domain, which results in turn in enhanced fracture toughness. The maximal increase of mode I and mode II fracture toughness and of flexural strength was obtained by the addition of 5% milled glass fiber. The mechanism observed suggests that crack propagation is stabilized even leading to its arrest/deflection, as a considerable amount of milled glass fiber filler was oriented transverse to the crack path. In contrast, at higher filler loading, tendency towards stress concentration grows due to local agglomeration and improper dispersion of excess fillers in inter/intralaminar resin channel, causing poor adhesion to the matrix, which leads to reduction in fracture toughness, strength and strain to failure. Fractured surfaces analyzed using scanning electron microscopy (SEM) revealed a number of mechanisms, such as crack deflection, individual debonding and filler/matrix interlocking, all contributing in various ways to improve fracture toughness.