First-Ply Failure Pressure of Symmetric Laminated Hybrid Composite CNG Tank

In recent years, compressed natural gas (CNG) as a fuel for the automobile is overgrowing, as it is cheap and environmental friendly compared to gasoline and diesel fuel. To improve fuel efficiency, lightweight composite pressure vessel tanks are used for the storage of CNG. Due to high specific strength, fiber-reinforced composites are most widely used. Synthetic fibers like carbon, glass fiber are used for the fabrication of these pressure vessels. In the last few decades, due to environmental concerns, the hybridization of synthetic fiber with natural fiber has gained the attention of researchers. This paper focuses study on the effect of adding natural fiber on first ply failure (FPF) pressure based on the Tsai-Wu failure criterion. The laminate stacking sequence on first ply failure pressure for carbon/epoxy, E-glass/epoxy, and hybridization of these fibers with abaca fiber is studied. Abaca is strongest among other natural fibers as it contains high cellulose which is responsible for strength of the fiber. CNG tank with a 30-liter capacity, inside diameter 261mm, thickness 12 mm, applied pressure of 25 MPa with both ends closed is considered. Stacking sequence of symmetric laminate [(90)2/∓θ/(90)2]S, for different orientation of helical winding i.e. θ = 15°, 25°, 35°, 45°, 55°, 60°, 75° is analysed for these composite materials. A hybrid tube made of synthetic and natural fiber with uniform thickness is considered. The simulation results of the first ply failure pressure are compared with theoretical results. Autodesk Helius Composite software is used for calculating material properties and, first, ply failure analysis. It is observed that burst pressure decreases as helical angle θ increases, and for the stacking sequence of [(90)2/∓15°/(90)2]S burst pressure is maximum for all tubes. The Burst pressure of the hybrid carbon/Abaca tube reduces by 69.5% to 42% for winding angle between 15° to 45° compared to standard carbon tube. For hybrid E-Glass/Abaca tube, burst pressure reduction was 21% to 4.7% for winding angle between 15° to 45° compared to standard E-Glass tube. For hybrid Carbon/Abaca tube, the drop in burst pressure is less 23.7% to 1.74%, respectively, compared to carbon tube for helical angle in the range 55° to 75°. Slight improvement in burst pressure (1.14% to 7.5%) is observed for the helical angle between 55° to 75° in the case of a hybrid E-Glass/Abaca tube compared to the E-Glass tube only. For the E-Glass tube, intermediate lamina can be replaced by Abaca fiber.