Composite Use in the Yacht Industry

Composites are fundamentally new types of materials created by using two or more materials together and possessing properties different from the materials that constitute them. Generally, when composite material is mentioned, fiber-reinforced plastic-based materials are understood. Following the development of the first modern synthetic plastics in the early 1900s, the properties of plastic materials began to develop into other material varieties by the late 1930s. Easy formability, lower density compared to metals, superior surface quality, and resistance to corrosion were influential in plastic development. Despite many superior properties, the low hardness and durability characteristics of plastic materials increased research efforts into reinforcement.

History and Definition of Yachts

People's interest in the sea initially led to maritime vessels used for military and commercial purposes; over time, as individuals' incomes increased, this led to their use for pleasure, sport, and travel purposes. The use of seas for recreational purposes has shown a continuous upward trend over the past 10 years despite various global crises. The Asian crisis, Argentine crisis, advances in information technologies, the stagnation the United States entered after 2000 as the world's largest yacht and cruise vessel market, the 11 September attacks, the Afghanistan and Iraq wars, and the 2008 crisis emerged as major crises of the past decade, particularly affecting the financial system and markets, bringing rapid rises and falls.

The selection of material for vessel production depends on vessel geometry and the production method adopted in the shipyard. The most commonly used yacht production materials in use today can be listed as follows;

• Composite, • Steel, • Aluminum, • Wood. Yacht and cruise vessel production statistics are provided in Figures 3.3 and 3.4. The United States is the world's largest producer with a 73.3 percent share, with approximately 760,000 vessels produced annually. ICOMIA 2008 statistics indicated annual global production exceeding 1 million units, consisting of approximately 120,000 inflatable vessels, 750,000 outboard motor vessels, 36,000 sailboats, 130,000 inboard motor yachts and vessels.

Modern Composites in Vessels

Since the 1950s, polyester and vinylester resins have developed steadily and GRP became the most common composite used in vessel construction. In shipbuilding, it is typically used for minesweepers, which require non-magnetic hulls. The osmotic problems encountered by early generation vessels are now a thing of the past with modern epoxy compounds. In the 21st century, volume CTP vessel production follows full industrial production processes. Wood/epoxy molding techniques are still typically used today for rowing boats. Since high-performance epoxy resins entered the market, other wood/adhesive composites have developed. Strip planking is a popular technique of this type for vessel construction: wooden strips (typically cedar) are placed lengthwise over frames and coated with epoxy. This simple construction offers an inexpensive and strong structure with a fair surface easily achieved by an amateur.

Advantages of Using Composite Materials;

a- Composite materials can be constructed from different layers and different combinations to obtain different mechanical properties, b- Composite materials show resistance to chemicals, corrosion, and weather conditions, c- They reduce the number of components due to the ability to produce complex parts as single units. Thus, production time is shortened by reducing intermediate assembly details and components, d- High strength/density ratio, e- High modulus/weight ratio. The most commonly used composite material combinations are: glass fiber+polyester, carbon fiber+epoxy, and aramid fiber+epoxy combinations. Composite materials can be applied in layered or thin layers. CTP (Glass Reinforced Polyester/GRP, FIBERGLASS) developed in the late 1940s is the most commonly used and the first modern polymer-based composite material today. Approximately 85 percent of all composite materials produced today are CTP and are mostly used in vessel hulls, sports vehicles, panels, and automobile bodies. The absolute reasons for preferring CTP and other composite combinations today and the increase in their use are their strength and lightness. It is possible to produce materials providing advanced benefits by reinforcing various plastic materials with fibers of ceramics, metals, or sometimes hard polymers. These material combinations, which are easy to shape thanks to the plastic they contain and extremely strong, hard, and light thanks to reinforcing fibers, are appearing in completely new application areas for composites every day. CTP Material Used in Yacht Manufacturing Glass Fiber-Reinforced Plastics The two main materials constituting CTP are resin and glass fiber. In the system, glass fiber forms the reinforcement and resin forms the matrix. Their correct interaction determines the properties of CTP. Apart from factors such as the glass fiber ratio in the composite and the geometry and direction of the glass fiber, the properties of the glass fiber and resin used are also determinative.

Resins Polyester Resin

Polyester resins are the simplest and most economical resin system. Unsaturated polyester resins in particular are the locomotive of the composite industry and constitute 75 percent of the total resin used. Polyesters are formed as a result of condensation polymerization of dicarboxylic acids and polyhydric alcohols (glycols).

Vinylester Resin

Vinylester resins were developed to combine the advantages of epoxy resins with properties such as "easy processing" and "fast curing" specific to unsaturated polyester resins. They are obtained as a result of reaction between epoxy resin and acrylic or methacrylic acid. This reaction occurs on an unsaturated end as in polyester resins when maleic anhydride is used. However, the locations of reactive portions are different.

Glass Fiber

Glass fiber reinforcement is present in 90 percent of plastic applications. The reason is that it is inexpensive and provides a good strength/weight ratio. In glass fiber production; various rocks combine in liquid form at approximately 1600°C to form glass. This liquid passes through very fine nozzles to form glass fiber strands with diameters of 9 to 25 microns. These strands then combine tightly to form fibers or loosely form rovings. These are subsequently coated with various chemicals to create adhesion properties in the strands and increase resistance to wear. Glass fiber shows good chemical resistance and easy workability. Future of Composites in Vessel Construction As production volumes increase, carbon fiber costs decrease, and therefore carbon fiber sheets (and other profiles) become more common in vessel production. Materials science and composite technology are advancing rapidly, and new composites contain carbon nanotube and epoxy mixtures. Recently, a small marine vessel concept project with a hull built using carbon nanotubes was delivered. Lightness, strength, durability, and manufacturing ease mean that composites will play an increasingly important role in vessel construction. Despite all new composites, fiber-reinforced polymer composites, while certainly in partnership with other exotic composites, will be here for many years to come.

Source 1- Seda ATEŞ GÜMÜŞ, "MOTOR YAT ÖN DİZAYNI VE EKONOMİK ANALİZİNE ETKİ EDEN PARAMETRELER", İSTANBUL TEKNİK ÜNİVERSİTESİ, FEN BİLİMLERİ ENSTİTÜSÜ 2- Yat İmalatında Kullanılan CTP Malzeme Ve İmalat Yöntemleri Bölüm I: El Yatırma Yöntemi, Çağın GENÇ and A.Armağan ARICI 3- https://www.greelane.com/tr/bilim-teknoloji-matematik/bilim/composite-materials-in-boats-820410