Composites and other lightweight non-metallic materials offer a number of advantages for shipping operators. The lighter weight of vessels whose hulls are built using composites allow for a reduction in engine power and subsequently fuel consumption. As a result, these materials provide environmental benefits alongside economic ones, as cost elements related to production, operation, maintenance and decommissioning of ships are all improved. These energy consumption advantages cross all stages of a ship’s life cycle.
For example, three-layer polymer composites can reduce the weight of a structure by 50-60% when compared to steel or 10-15% when compared to aluminium, as well as improving ship stability and hull fire safety when compared to aluminium.
Aside from these environmental benefits, composites can also increase cargo capacity and create aesthetically-pleasing vessels at a reduced cost compared to those made of steel.
Non-metallic composite materials have been used for smaller vessels for years, but have not been widely used for the manufacture of larger ships, which were conventionally built using steel.
Projects such as the TWI-assisted Fibreship project worked to research the use of fibreglass to reduce weight, operating costs and fuel consumption while increasing the life cycle of large vessels.
Broadly-speaking, non-metallic materials used in shipbuilding include various types of timber and plastic.
Timber
The low cost and low volume weight, coupled with its strength and ease of processing makes timber a popular material for ships. Used for hulls, decks, cladding, bulkheads, insulation battens, equipment detailing and more, timber generally comprises 15% of a ship’s body weight.
Coniferous woods like cedar, fir, pine., larch and spruce are all used in the shipbuilding industry as well as deciduous woods like ash, bakaut, birch, mahogany, oak and teak. Of these, bakaut is favoured as a material for stern-bearing shells as it is hard and able to operate in water without lubrication.
Many timbers used in shipbuilding are impregnated with antiseptic solutions to prevent them from rotting, while antipyrine is also used to improve its fire resistance.
Plastics
A variety of different organic and synthetic plastics have found use in shipbuilding, including those that have been mixed with other filler materials to impart properties such as increased strength and heat resistance. Foaming agents are also used to make some resins gas-filled so that they can be used as heat or noise insulation in ships. Commonly used plastics for ships include non-metallic materials-laminated plastics, extrusions, mouldings, singleskin and sandwich structures, structural plastics, and glass reinforced plastics. As well insulating purposes, plastics use on ships includes for structural finishing, furniture, cladding, and corrosion protection.
Plastics do have some potential disadvantages however, including low thermal resistance and conductivity, and a low modulus of elasticity.