Composite ships for the next generation of ship owners
A new era is dawning in the shipbuilding industry, one where traditional construction materials are being replaced with composites. These modern materials yield numerous advantages.
The use of composite materials has really expanded in various industries over the decades. “These materials have been used in bridges and buildings, trains, trams and cars,” says Damen Business Development Manager Composites Marko Paš. “Even the highly loaded structures of modern passenger aircraft are made from over 60% composite materials.” The point is that, if designed and built correctly, composite materials can perform their purpose better than metals.
But what exactly are composites? “They are materials made from two or more constituent elements, each with significantly different physical or chemical properties that, when combined, produce a material with characteristics different from the individual components,” Mr Paš explains. “Concrete, tarmac and plywood – composites have a big impact on our everyday life.”
Looking specifically at the shipbuilding industry, three elements are used to create composite materials: fibres, core materials and resins. “Fibres are the structural element, usually glass or carbon fibres. They can be produced in different lengths and weaved into different shapes. Core materials, such as closed cell PVC or SAN, are used for one main reason: “To make lightweight, but stiff and safe construction panels. Cored or “sandwich” construction creates very good impact absorption characteristics. Resins like polyester, vinyl ester and epoxy-based polymers connect the fibres and core to form stable, load-bearing structures.”
Using these three components, shipbuilders like Damen can offer a series of key advantages with composite vessels. “Reduced operating costs is a major benefit. Because a composite vessel can be up to 30% lighter than a comparable aluminium vessel, fuel consumption – and costs – can be significantly decreased.” For example, a case study of Damen FCS 1605 vessels has shown that composite vessels, depending on installed equipment, are at least 10% lighter than their aluminium equivalents.
This translates to fuel savings of more than 60,000 litres per year with the same range and speed as an aluminium version – based on an operating profile of 4,000 sailing hours per year.
Vessel operating costs are further reduced due to the fact that composites do not corrode or degrade with time. Moreover, the problematic matter of blistering on underwater surfaces is no longer an issue due to improved material properties, proper material selection and modern production techniques. Nowadays, once a composite material is cured, the only maintenance required is cleaning with solvent and water.
As well as being light, composite materials are also strong and not vulnerable to fatigue. The ‘sandwich’ construction of cored composite panels is very good in absorbing impacts with floating objects, other vessels or infrastructure. If the outer skin is penetrated under the water-line, water absorption remains localised due to the closed cell characteristics of the core.
Front face drop test
Damage on front face of 5mm aluminium and 25mm cored composite panels.
Aft face drop test
Damage on inner face after 15 kg weight drop test: aluminium plate is penetrated and takes water (intact composite panel inner skin)
Drop test shows that 5 mm aluminium plate gets penetrated by 15kg weight dropped from 5 m height. Composite panel outer skin gets penetrated, but energy gets dissolved into 25mm core. No immediate need for repair while hitting floating objects or infrastructure, while aluminium vessel is taking water and needs immediate repair action.
Drop test is available to attend for Damen clients in order they want to witness composite mechanical performance.
If repairs are required, they can generally be carried out by a local workforce with inexpensive equipment.
It can be said that one particular advantage of composite materials means that it is very suited to Damen’s own principles.
The very nature of composite vessel production is that it is a repeatable process – composite vessels are ideal for series construction. This produces vessels faster and with shorter delivery times.
And it is this last feature that Damen calls into effect at its yard in Antalya, Turkey. In operation since 2012, the yard specialises in composite vessel production. “We build twelve different designs here at Damen Shipyards Antalya,” informs Mr Paš. “These are the Damen RHIB, Interceptor 1102 and 1503, FCS 1204, SPa 1204, SPi 1505, SPi 1605, FCS 1605, SPa 1605, SAR 1906, SPa 2205 and the 24-metre Water Bus.”
Since its inception, the yard has fine-tuned the production process to such a degree that the composite construction technique used is called ‘Damen Infusion Lamination’. According to Mr Paš, this vacuum production process has a lot of benefits over hand lamination techniques.
Infusion process video
Stronger & lighter
“First of all, the end product is stronger,” he says. “To achieve the best mechanical properties, the typical resin content of a composite is 30-35% by weight. The vacuum infusion process helps us achieve this by reducing the amount of resin, leading to a relatively higher fibre content.” Still on the subject of strength, the vacuum infusion process can be combined with foam cores for more advanced laminates. This greatly increase stiffness for a low weight penalty. “Cores enable bigger panels, less internal stiffening and so a clearer internal layout. They are also better at absorbing impact damage.”
“Secondly, it produces even lighter products. The fibres that we use with vacuum infusion are much more mechanically efficient compared to the chopped and woven fibres used in the classic hand lamination process. Therefore, we require less fibre, as well as less resin, which leads to even greater material and weight savings for the same strength.” This lightness has an impact on efficiency and speed: “Operators can attain higher speeds, or carry more cargo with the same power and fuel consumption. Alternatively, they can decide to use smaller engines, or use less fuel for the same speed.”
A new era begins?
Mr Paš continues by highlighting how composite vacuum infusion leads to quality vessels. “All parameters such as temperature, humidity and vacuum levels are easily repeatable so there is complete traceability of materials and conditions during the lamination process. Using industrial equipment for the vacuum, resin mixing and resin quantities removes almost all mistakes normally caused by human error.” Reflecting Damen’s focus on quality, the yard has a production-independent quality control team, following every part produced and keeping records on compliancy with drawings and best practice standards.
To date, the 50-strong team at Damen Shipyards Antalya have built a total of 78 Bureau Veritas and Lloyd register-certified vessels. The focal point of the yard is series production that implements standardised details and materials. “As such, we have a lot of the individual components already on stock, ready for assembly when an order is finalised. This means we can deliver some designs in three to seven weeks.”
Looking at the vessel types available (all fast, light and state-of-the-art), it is clear that the shipbuilding industry, which historically has been very conservative to innovations, has started its progression into a new era of production.