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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Basalt/epoxy composite pipes in a [±55]4 winding configuration were produced on CNC filament winding machines (10 N fiber tension and ~11 mm bandwidth). In the experiments, a 34 m/s impact velocity was set using the double-disc method, and five different particle impingement angles (30, 45, 60, 75, and 90°) were used to determine the erosive effect on the outer surfaces of filament wound composite pipes under the influence of 600 mm erodent particles with angular geometry in the test set, complying with the ASTM G76-95 standard. The winding patterns in the lamina (±55 angle-ply laminate region) and zigzag (±55 zigzag region) regions of BFR/EP pipes were determined to have significant effects on solid particle erosion resistance, as evidenced by the SEM images.

The study's main motivation is to determine the creep behavior of high‐density polyethylene (HDPE)‐based nanocomposites in unexpected situations where short‐term constant loading may occur. On this basis, the short‐term creep behavior of 1 wt.%, 3 wt.%, and 5 wt.% nanoclay reinforced HDPE nanocomposites were investigated at room temperature (23 ± 1°C) and strain rate of 1E‐4 1/s under 8, 12, and 16 MPa stress levels. As the nanoclay reinforcement ratio by weight increased, the creep resistance and modulus of neat HDPE increased at 8 MPa stress level, but they decreased at 12 and 16 MPa stress levels. The absorbed energy that corresponds to the area under the stress–strain curve increase as the stress level increase from 8 to 16 MPa. However, absorbed energy decreases as nanoclay reinforcement increases for 8 MPa. The curves produced from the four‐element Burger's model and Findley's power law models were compared with the creep curves obtained from the experiments. The four‐element Burger model was found to fit the creep curves better than Findley's power‐law model. Also, some regression curves were given for interpolations to give intermediate values of the maximum creep strain values at different stress levels. The presented models can be used to evaluate creep strain, considering the usage fields of parts or semi‐products produced from nanoclay/HDPE nanocomposites.

In this study, the fatigue behavior of 0.25 wt.% graphene nanoplatelets (GnPs) reinforced and unreinforced impact damaged basalt/epoxy composite pressure vessels (CPVs) was investigated. The CPVs were subjected to low-velocity impact (LVI) of 2.5 J, 5 J, 7.5 J, 10 J, 15 J, 20 J, and 25 J under internal pressure of 50 bar (hoop/axial prestresses: 98/49 MPa). Then, to detect fatigue life changes, fatigue tests were performed at load rates of 30% of ultimate hoop stress (σHS), where sweat damage occurred in the basalt/epoxy CPVs under alternating internal pressure. Considering the remaining fatigue life and formation of the damages in the CPVs for all impact energies, to investigate the fatigue behavior and GnPs effects of CPVs subjected to low-velocity impact, an impact value of 5 J was preferred. The 5 J impact damaged CPVs were subjected to fatigue cyclic following ASTM D 2992 at load rates of 20%, 25%, 30%, 35%, and 40% of the σHS. The fatigue life of damaged CPVs was compared by that of undamaged over S-N curves. As the impact energy increased, the impact damage area increased. The increased size of damage reduced the fatigue life of basalt/epoxy CPVs. At the fatigue load rates mentioned above, the GnPs improved the fatigue life of damaged basalt/epoxy CPVs by about 3.5, 3.2, 11.3, 2.4, and 5 times, respectively.