Investigation on Mechanical Properties of Filament Wound Composites for Pressure Vessel

Abstract

Metallic pressure vessels or cylinders used over many decades for processing food and beverages products, transportation of chemicals, storage of hazardous and nonhazardous chemicals for prolonged durations have been carrying limitations throughout their service period. Few limitations such as, the weight of the cylinders, corrosion and erosion effect, risk of sudden failure. The current study is connected to development of an alternative material for existing metallic cylinders to overcome few limitations. In the present study, filament wound GFRP (Glass fiber Reinforced Polymer) is proposed, which is having high strength to weight ratio compared to the existing metallic material. The FE (Finite Element) analysis of cylindrical pressure vessels used for LPG storage is carried out by alternative materials such as LCS (Low Carbon Steel), Aluminium 6061 T6, and GFRP. Based on maximum specific strength, the best alternative material obtained among others is GFRP, and this material is chosen for further studies. The GFRP pressure vessel cylinder is further studied by varying filament winding process parameters such as fiber volume fraction (0.55,0.65,0.75), winding angle (±45°, ±50°, ±55°, ±60°, ±65°, ±70°,±75°) and stacking sequence (SS1, SS2, SS3, SS4, SS5, SS6) using FE analysis tool. A total of 336 FE simulations were carried out, i.e., with PVC (Poly-Vinyl Chloride) liner (168) and without PVC liner (168). The optimization tool MCDM (Multi criteria Decision Making) VIKOR method is used for the selection of best alternative among existing 168 FE simulation compositions (with PVC liner). The liner act as leak-proof material in filament wound composite vessels and hence can be used for storage or processing of different viscous and non-viscous fluids. The optimization of the FE simulation result leads to best attribute, which is selected and fabricated as per its respective fabrication iii process parameters for experimental studies. Similarly, next to five attributes are selected as per available testing laboratory facilities (physical, mechanical and tribological, hygrothermal ageing). The filament wound GFRP cylinders are cut into test coupons for physical, mechanical, and tribological characterization studies. Further hygrothermal ageing of all 6 compositions are studied. In hygrothermal ageing effect is studied using three different fluids such as tap water, sea water, and tap water with oil. The hygrothermal ageing is carried out for a period of 45 days at a constant temperature of 80°C. The aged and unaged samples are subjected to mechanical tests such as hoop tensile strength, tensile, compression, and bending tests. The mechanical test results are compared for a possible reduction in strength of aged filament wound GFRP samples. The obtained results are further examined with fractography study using Scanning Electron Microscope (SEM). The different mechanical testing results (ultimate tensile strength, ultimate compressive strength, ultimate flexural strength, hoop tensile strength) highlights that the filament wound GFRP samples are moderately affected by ageing. In overall, in the case of FE simulations studies, the product with composition of fiber volume fraction, Vf = 0.55, winding angle = ±55° and stacking sequence of (±55°2/90°2/±55°2) is suggested as the best alternative or attribute-based on average Von Mises of 45.64 MPa and hoop stress of 44.82 MPa compared to other compositions. As far as the experimental study of filament wound GFRP test coupons is concerned, retention of important mechanical properties such as tensile, compression, flexural, and hoop tensile strength is the main factor. Hence it is observed from different hygrothermal ageing effect studies that filament wound GFRP material with 1200TEX is least or moderately iv affected by hygrothermal ageing. The product which has the least ageing effect and having the highest strength (hoop tensile, tensile, compression, and flexural strength) retention rate (nearly 90%) is product-P1(055WA55SS1) with compositions of fiber volume fraction, Vf = 0.55, winding angle of ±55º, stacking sequence of SS1 = (±φ°2/90°2/±φ°2). Hence this product P1 can be suggested as an alternative material to existing metallic material for elevated temperature applications (up to 80ºC).