The of plane compressive properties are more critical,


The use of composite sandwich structures in aerospace and marine applications is increased due to their extremely low weight that leads to reduction in the total weight and fuel consumption, high flexural and transverse shear stiffness, and corrosion resistance (ASM Handbook 1987). Also sandwich materials are capable of absorbing large amounts of energy under impact loads which results in high structural crashworthiness. A structural sandwich is composed of two thin stiff face sheets and a thick lightweight core bonded between them. Asandwich structure will give different mechanical properties with the use of different types of materials because the overall performance of sandwich structures depends on the properties of the constituents. Various combinations of core and face sheet materials are utilized by researchers worldwide in order to achieve improved crashworthiness .                                         In a sandwich structure, generally, the force couple formed by the face sheets carry the bending loads and the lightweight core material carries the shear loads. The face sheets are strong and stiff in both tension and compression as compared to the low-density core material whose primary purpose is to maintain a high moment of inertia. Because of the  low density of the core material the panel density will be low so that  under flexural loading of  sandwich panels there will be  high specific mechanical properties relative to the monocoque structures. Hence, sandwich panels are much more  efficient in carrying bending loads. The face sheets act together to form a force couple, where one laminate is under compression and the other under tension during flexural loading and  the core of sandwich material  resists transverse forces and stabilizes the laminates against global buckling and local buckling. They also yield an increase in buckling and crippling resistance to shear panels and compressionmembers. In automotive industry the out of plane compressive properties are more critical, whereas in wind turbines the in plane compressive properties are more importance hence, the critical properties of sandwich composites vary according to the application area ofthe structure. The objective of this study is to understand the mechanical behaviour  of multi layered sandwich structures with polyurethane core and glass fibre face sheets fabricated by vacuum bag moulding technique. In this project, flatwise compression (FC), edgewisecompression (EC), Mode I inter laminar fracture toughness and three point bending (3PB) tests were conducted on multi layered sandwich specimens

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