PSI - Issue 25

Dalbir Singh et al. / Procedia Structural Integrity 25 (2020) 159–171 Dalbir singh/ Structural Integrity Procedia 00 (2019) 000 – 000

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vinyl ester resin when subjected to higher exposure duration or higher temperature solutions. They had concluded that the microstructure of polyester material degrades more rapidly than the microstructure of bis-phenol-A epoxy vinyl ester resin under acidic and high- temperature exposures, which can be justified by diffusion of Sulphur into the cracks and the increased surface cracks and roughness. Amaro et al., 2013a; A. M. Amaro et al., 2013b) reported the effects of alkaline and acid solutions were compared its effect on to glass/epoxy composites. The authors illustrated that the lowest flexural properties are observed when an alkaline solution was used, which suggests that the alkaline solution is more aggressive than the acid solution. The hydrochloric acid used in the study was responsible for the worst results in terms of acid solutions. The samples immersed in alkaline solutions displayed a decrease in matrix mechanical properties and the roughness observed was due to ultra-micro indentation. Many researchers have reported that the effects of acidic and alkaline solutions on the mechanical properties of composites are strongly dependent on the exposure time, concentration and temperature of the solution. (Mahmoud and Tantawi, 2003) report ed that the exposure time had a significantly influence on the Flexural strength, Hardness and Charpy’s impact resistance of the composite material. When the samples were e xposed to acids at 100 °C the mechanical properties and change of weight were observed by the authors. Sulphuric acid has a more severe effect on the strength when compared with the other acids . (Stamenović et al., 2011) found that the ultimate Tensile strength and modulus of a composite significantly decrease with increasing pH value. They also observed that tensile properties are proportional to the exposure duration. According (Mortas et al., 2014) the corrosive environment was highly dependent on the concentrations of solutions and a decrease in the impact strength was observed. Finally, the mechanical properties of the composite materials decreased when subjected to acidic solutions at high temperatures. (Amaro et al., 2014) tested the glass fibre/epoxy composites under the influence of universal multi-grade engine oil (15W-40) and an extra high-performance hydraulic brake fluid (DOT 4), It was found that both solutions affect the flexural properties and the impact strength of the composite samples. (Kim et al., 2018) studied the effects of microscale oil penetration on mechanical and chemical properties of carbon fibre/epoxy composites. They confirmed that after oil absorption for 24 h by the laminate, the mechanical properties decreased. They also concluded that exposure to high temperatures caused the epoxy polymer to form a dense cross linked epoxy network. There are several studies about the effect of mechanical properties of composite materials when they are subjected to moisture, hydrothermal and aggressive solutions. From this literature knowledge, it is evident that the study about the mechanical characteristics of carbon fibre composites under the effect of different aviation-grade fluids was not yet studied . Thus, the aim of this paper is to study the material’s degradation under the exposure of three different aviation-grade fluids: Avgas-100LL, Aviation Turbine Fuel (ATF-K50) and an extra high-performance lubricating fl uid (OX-38). In this article, the realization of the degradation of mechanical properties is evaluated in terms of Tensile, Flexural and Impact strength. According (Banna et al., 2011) tensile and bending tests were selected because these tests are the most sensitive to changes of exposure conditions and duration. The total energy dissipated in the material before final failure occurs is the measure of the impact resistance of a composite material. 2. Material and Experimental procedure Carbon fibre Composite material laminates were manufactured from commercial bi-directional carbon fibre 200 gsm grade and Resol- based phenolic resin (Ph); in a ratio of 60:40 by weight, as the composite’s reinforcement and matrix, respectively in the laboratory. The laminates were manufactured with the stacking sequence of 16 layers. The processing consisted of several steps: Hand Lay-Up method, application of 5kgf/cm 2 of pressure in compression moulding machine where the temperature was maintained at 270 0 C, maintaining pressure and temperature for about 30 min, cooling down to room temperature while maintaining the pressure and finally detaching the laminate from the mould. The laminates were manufactured to a useful size of 300 x 300 x 3.2 mm 3 . The specimens used in the experiments were cut from these thin plates, using a water-jet cutting machine. The Tensile, Flexural and Impact test samples are shown in Fig.1