How Composite Materials Are Put To Use In The Marine Industry
Can you guess when the first composite material was made? Or can you guess what it was?
You may be thinking of an early composite like fibreglass which has been around for quite some time now. But in fact, the first bonded composite material dates back to 1200AD…
The Mongolian empire invented the composite bow by combining wood, bamboo, bone, cattle tendons and silk which were bonded together with natural pine resin.
The idea of bonding different materials together to make a new material (that has many of the strengths of its component parts) was an instant success for the Mongols. Their bows were smaller, lighter, and more powerful than anything the world had ever seen. They were the most feared weapon in the world right up until the invention of firearms 200 years later. The success of Genghis Kahn was partly down to their discovery of composite materials.
But enough of the history lesson. Let’s get back to the modern day.
Before the invention of modern composite materials, engineers were limited. If you wanted durability and strength, it was usually going to mean a whole heap of weight. This weight caused its own set of issues, especially for marine applications.
Today (as you probably already know) we have a wide range of composite materials available to us, many of which have quickly become the materials of choice for various marine uses. Here we are going to take a look at some of the more common materials and take a look at why they are so popular among engineers.
Fibreglass was an accidental invention (like most of the best things we take for granted these days). Researchers were experimenting with glass fibres to replace mineral wool which was being used for insulation at the time.
The incredible properties of their accidental discovery spread around the world like wildfire, and in less than a decade the marine industry was transformed forever. From surfboards to superyachts, these days over 90% of yachts are made with some form of fibreglass. However, we no longer use the glass fibres that the original researchers experimented with. They have been replaced by a silica-based material which further increases the durability of the already resilient glass fibre.
There are two main types of Fibreglass that are commonly used in marine applications, E-Glass and R-Glass (aka S-Glass).
E-Glass is the benchmark that all other composites (and non-composites) are tested against. If you want to compare a new material to something, you compare it to E-Glass. It’s lightweight, cheap, strong, durable, and long lasting - so it’s easy to see why it's so popular.
However, regardless of how good E-Glass is there is room for improvement, which is where R-Glass comes into the picture. R-Glass (Reinforcement Glass) aka S-Glass (Strength Glass), is stronger, lighter, and tougher than E-Glass – but it is around 300% to 400% more expensive.
The next revolution in composite materials came around reasonably quickly after fibreglass had taken the world by storm. The cat was out of the bag about hardening fibres of various materials with a resin. People were experimenting with everything and anything they could find.
Arguably the most successful composite to come out of the post fibreglass arms race was carbon fibre. It improves upon fibreglass in many ways, and as an added benefit many people love the way it looks. Used widely throughout sailing teams where performance is critical, carbon fibre is abundant in luxurious powerboats and leisure yachts for aesthetics and to demonstrate that no expense was spared.
Carbon fibre is around 6 times more rigid than E-Glass, it doesn’t rust or corrode like some metals and is incredibly lightweight. You could not purpose build a material that is better than this for the marine industry.
The bottom line is that the strength to weight ratio is off the charts. When it was invented engineers were suddenly able to access a material that was:
70% Lighter than steel and up to 10 times stronger
40% Lighter than aluminium and up to 8 times stronger
The only issue is that carbon fibre is not cheap. It’s one of the most expensive commonly used composite materials in the world. However, despite this price tag, there seems to be an insatiable demand for carbon fibre’s amazing properties (which shows no sign of slowing down).
Another factor that manufacturers must consider is the added hazards accompanied with handling carbon fibre. The fibrous nature of the material means that harmful strands can become airborne at any moment. Containing hazardous carbon fibre dust is an added expense not always considered in preliminary project budgets.
Aramid (which is a combination of the technical term Aromatic Polyamide) first became popular in the superyacht industry around the same time as carbon fibre. The technical details on how members of the Aramid family are made are a little bit out of scope for this article. But in a nutshell, they are made from stiff polymer chains linked by strong hydrogen bonds.
Probably the most well known Aramid is Kevlar®, but there are others (like Nomex®) which are also worth a mention.
Aramids are characterised by incredible strength and durability without the weight of metal. They are commonly used in the marine industry but need to be combined with another composite because they have one fatal flaw…
They can absorb water.
As you can imagine, this is not the kind of property that would be useful in marine uses. But when protected from water by another composite, the strength of Aramids can be put to good use.
With the exception of E-Glass, all of the composite fibres on this page have one thing in common. They are all reasonably expensive when being used on a project the size of a superyacht.
Engineers discovered that it was possible to sandwich a cheaper material (like foam or balsa wood) in-between layers of composite and increase thickness and stiffness without excessive cost. Sandwiching allows any unexpected stress (like an accidental impact) to be spread across a larger surface area, reducing the risk of deformation.
The technique can be used with any of the materials on this page, and often involves more than one of them.
You could almost say it’s like making a composite out of composites…
If there is one thing we can be sure about, it's that we have not seen the end of composite materials. Research is still being conducted to this day on new materials that could provide greater strength with a better weight ratio.
Developments like carbon nanotubes have scientists and researchers around the world lying awake at night dreaming about the possibilities.
And occasionally, we do too…