Hybrid Composites for the Design and Development of Pressure Vessel for Underwater Applications

The study's main objective is to design and develop pressure vessels in underwater applications using Hybrid composites-Fibre Metal Laminates (FML) so that the weight will be reduced. The proposed pressure vessel accommodates electronics in the underwater ambient noise measurement system under an external hydrostatic pressure of 1 MPa (10 bar). The research study aims initially to design and develop a pressure vessel with stainless steel 316 L and subsequently design a pressure vessel with hybrid composites with a combination of composite materials of E-glass and carbon/epoxy materials with a metal alloy stainless steel 316 L. The pressure vessel has been optimised with varying metal and composite percentage combinations. The cylinder's wall thickness has been pivotal in optimizing pressure vessel design. Classical Laminate Theory (CLT) transforms the FML pressure vessel or cylinder into a rectangular plate. As preliminary measures, FML specimen with a size of 0.45 m square laminate and 0 degrees orientation has been developed with 50 % metal layer and 50 % fibre composites, and corresponding mechanical tests have been carried out as per the standards. The tensile strength of the developed FML is 420 MPa compared to base metal (SS316 L) strength of 556 MPa, and similarly, Flexural and Impact properties have shown a higher level when compared to other types of FMLs.