Hygrothermal deterioration in carbon/epoxy and glass/epoxy composite laminates aged in marine-based environment (degradation mechanism, mechanical and physicochemical properties)

Abstract

One of the major challenges in off-shore tidal and wave energy devices is the ageing of these structures in the hostile marine environment, which limits their operating life. In this research, mechanical properties of aged glass/epoxy and carbon/epoxy composite specimens including tensile strength, Young’s modulus, flexural strength, and shear strength, following immersion in a representative accelerated marine degradation environment (artificial seawater, with 3.5% salinity at room temperature and 60 °C) have been investigated. The microstructure and physicochemical characterization of the aged samples were assessed via microscopic imaging, micro-CT scanning and differential scanning calorimetry. The degradation phenomenon was apparent in the change of mechanical properties and microstructure of composite laminates (micro-cracks and debonding between matrix and fibre). Generally, the ageing process had a more severe effect on tensile and shear strengths of glass/epoxy samples than those of carbon/epoxy specimens. Reversely, the results of bending tests of carbon/epoxy composites showed more drop-in flexural properties than glass/epoxy samples. The results revealed that degradation mechanisms continue even after reaching the saturation point in composite materials. The achievements of this research present a good understanding of the effect of degradation of composite materials in salt water to deal with their application in real service environment.

Tensile behaviour of unaged and hygrothermally aged discontinuous Bouligand structured CFRP composites

“…Temperature accelerates the rate of water diffusing into composites [31][32][33][34] and this in turn accelerates cross-linking and thus the embrittlement of the composite material [34,35]. A series of recent papers evidence that the elastic modulus, tensile strength and bending strength of carbon fibre/epoxy composites are reduced when under the ageing conditions of 3.5% salinity at 60 C water temperature [36][37][38]. The mode of loading is understood to affect composites with different ply angles and has been reported to cause degradation in tension-compression fatigue to a greater extent than in tension-tension loading and this has been attributed to fibre-matrix debonding coupled to the deterioration of matrix properties [39].…”

Multi-scale modelling and life prediction of aged composite materials in salt water

“…In addition, chemical-based mechanisms lead to changes to the polymer matrix that are not reversible and occur primarily due to hydrolytic deterioration, whereby the diffusion of water into the composite causes chain scission. 20…”

Mechanical behaviour of fabric-reinforced plastic sandwich structures: A state-of-the-art review

“…This led to the investigation of several failure modes including indentation/cracking, face sheet buckling, delamination within the face sheet, and disbonding between the face sheet and the core. [37][38][39] Research conducted in this area can be classified into three main fields; experimental, 40,41 numerical, 42 and nondestructive test methods (NDTs). 19,43,44 This review presents the findings of recent experimental and numerical studies on the performance of FRPSS subjected to quasi-static and dynamic loading with or without environmental degradation.…”

“…This led to the investigation of several failure modes including indentation/cracking, face sheet buckling, delamination within the face sheet, and disbonding between the face sheet and the core. 37–39 Research conducted in this area can be classified into three main fields; experimental, 40,41 numerical, 42 and non-destructive test methods (NDTs). 19,43,44…”