This research studies the effect of the addition of graphene nanoplatelets (GnPs) on the mechanical behaviour of composite pipe materials exposed to hydrothermal ageing, aiming to increase their service life. For this reason, 0.25 wt.% GnPs reinforced and unreinforced filament wound basalt fibre reinforced epoxy composite pipes (BFRPs) were produced. BFRPs were exposed to a hydrothermal ageing process in order to examine the effects of water absorption behaviour on mechanical properties. Hydrothermal ageing processes were carried out by immersing the samples in distilled water at 80°C for different periods such as 15, 30, 45 and 60 days. Following the ASTM standards, the tensile, density and hardness properties of water-exposed GnPs reinforced and unreinforced BFRPs were examined and compared with unexposed specimens. As a result, while water absorption caused a remarkable loss in the mechanical properties of BFRPs, the adverse effects of water absorption on mechanical properties were minimized by the presence of GnPs.

The purpose of this study is to investigate the impact behavior of composite pressure vessel (CPV) in-service case. Additionally, graphene nanoplatelets (GnPs) were introduced to epoxy resin. [±55 ] 4 basalt/epoxy specimens were manufactured using the filament-winding method, and the low-velocity impact (LVI) response was investigated. The LVI tests of CPVs were performed at energy levels of 2.5, 5, 7.5, 10, 15, 20, and 25 J under 50 bar internal pressure. The prestress value considering the internal pressure used under service conditions was taken as 1:5 of the burst pressure of the basalt/epoxy CPVs. After the LVI tests, the contact force-time and force-displacement curves were acquired. Also, absorbed energy values by CPVs were calculated over the obtained curves. The effects of GnPs on damage formations on basalt/epoxy CPVs under LVI loads were evaluated based on microscopic analysis. According to evaluations, damage formations such as matrix cracks on outer and inner surfaces of CPV, transverse cracks, and delamination were detected. Test liquid was detected on the impact surface at 25 J LVI test. The leakage observed due to the 25 J impact energy proves that damages can result in a leakage path. Consequently, the areas of damage formed in the cross sections perpendicular to the axis of basalt/epoxy CPVs decrease with the addition of GnPs, and the CPVs are more resistant to LVI effects.

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Two different nanosized mineral fillers (nano calcium carbonate and nanoclay) were used in the high density poly(ethylene) (HDPE) composites pilot plant production. Structural and mechanical properties of the prepared composites were examined in this study. The homogenous filler distribution was confirmed in the tested samples by scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy analyses. The fillers’ fortifying effect on polymer composites’ mechanical performance was confirmed as indicated by the increased elastic modulus and indentation modulus. Additionally, the possible modulation of the plastic-elastic mechanical behavior was confirmed by the type of the filler as well as its concentration used in the final composites testing articles.

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