The body of a craft is subjected to a series of complex loads, both static and dynamic. The global strength of such a body is given by the entire assembly of the hull, deck and strengthening framing system, all of these components working together [1]. Such a boat must first of all fulfill a very important requirement, namely: minimum hull resistance so that the engine power would primarily be used to achieve the highest possible speed. This can only be achieved if the hull wetted surface is as small as possible, which leads to the need to reduce the hull asembly weight. Thus, in this paper there are proposed and tested a number of nine lamination alternatives for the initial structure, designed as a sandwich system with different types of core materials. From the total nine alternatives, three of them are hybrid structures in which there are explored structural alternatives with several types of core materials. The verification of structures obtained with the proposed materials and lamination schedules was made using numerical methods both for naval hydrodynamics to determine loads and for naval structures for global body strength and analysis.

As in many industrial domains, applications of composite materials show a constant growth in the marine industry. The possibility to create a specific combination of materials and engineering proves that they work together better than any of them independently, thus generating a wide range of applications that challenge the naval architects of today. The paper presents a brief review of the development of this class of materials and their advantages for the shipbuilding and boatbuilding industry.

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Glass reinforced plastic, so called GRP, is a composite material made of glass strands called fibbers woven together to create a flexible fabric. GRP is a lightweight material with many and diverse applications ranging from the manufacture of reservoirs for different liquids to the manufacture of boats, yachts, chairs and even children playground furniture. The behaviour of this material under static and dynamic loads is still raising interest from the scientific community and a large number of researchers. This continued interest is due to the material versatility for different applications depending on its manufacture process that has a significant weigh-in in the material mechanical properties. These resulting mechanical properties need to be carefully analysed and benchmarked prior to using the obtained material in commercial applications. The scope of this research study is to analyse the behaviour of glass reinforced plastic plate panel with reinforcements on one and two directions under static and dynamic loads employing both experimental and numerical methods for results validation. The methods used in this research study for the dynamic loads can also be applied successfully to other composite materials. Additionally, the stress plots have been analysed in iteration in order to ensure the most optimal reinforcement pattern.

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