Characterization of Fiber Metal Laminates for the Development of Subsea Housing

Abstract

Fiber Metal Laminates (FML) are hybrid composites comprising metals and Fiber Reinforced Plastics (FRP). FMLs are the most widely used in aerospace, defence and automotive sectors due to their superior qualities like light weight, tensile, compression, flexural, excellent fatigue and impact resistance. The properties like strength-to-weight ratio, susceptibility to corrosion and good heat conduction of FML make it suitable for subsea applications. Commonly, FML with a combination of aluminium (Al), titanium (Ti), stainless steel (SS) alloys and FRP are widely used for ocean applications. Compared to other FML, the SS alloy-based FML is typically used in subsea applications as it has more creep and excellent corrosion resistance. In India, under the Ocean Acoustics programme of the National Institute of Ocean Technology (NIOT), an autonomous underwater Ambient Noise Measurement System (ANMS) has been developed and deployed in the shallow waters of Indian seas for the past 12 years to study the background noise prevailing in the sea. To accommodate electronics and power packs for the measurement of ambient noise at an ocean depth of 100 m, subsea housing with stainless steel 316L (SS316L) material for a pressure rating of 1 MPa has been developed. The objective of this study is to develop the FML with SS316L and FRP for reducing the weight of the housing. Based on the literature studies and Classical Laminate Theory (CLT), the FML has been fabricated as a 0.45 m (450 mm) panel with a sequence of SS316L as outer layers and E-glass fibre and carbon as the inner layers. The total thickness of the laminates is 0.006 m (6 mm). The developed FMLs are processed with water jet cutting machines to carry out various testing such as tensile, compression and flexural, which are relevant to the characterization of FML and the experimental results are described in the paper.