Composite construction is one of the oldest methods of building known to man. The craft of weaving fibre to create strength goes back thousands of years – the original mud hut is the first example of composite building, straw or sticks woven together and held in place by mud. Today we use a range of natural and engineered fibres in place of straw, and the mud has been replaced by a range of resin systems all with a huge variety of mechanical attributes.
Of course our manufacturing needs have changed as well. No longer is it the simplicity of the mud hut. Rather, today’s architectural designs call for innovative solutions to meet the demands of increasingly complex form and structure. The latest developments in the world of advanced composites mean almost any shape you can imagine can be manufactured as lightweight structures – with the required rigidity and strength to allow extraordinary architectural design.
So what exactly are “advanced composites”? In general terms advanced composites are not widely understood. Terms such as GRP (Glass Reinforced Polymer) or FRP (Fibre Reinforced Polymer) give a misleading impression of consistency and uniformity. It is reasonable to use these generic terms to describe and group low quality, mass-produced parts such as truck bonnets or swimming pools. However, it is dangerous if you don’t recognise the huge difference between such mass produced parts and the highly engineered, structural facades that are adorning more and more high profile buildings, 30 stories up. While mild steel and titanium could both be described as “metal”, the performance characteristics are profoundly different. The same range applies in composite manufacturing.
The preconception of composites as used only for “cheap” products simply reflects a lack of understanding. The reality is advanced composites should be seen for what they are – a 21st Century structural textile. A smart, sophisticated response to a design challenge.
Every input has an impact
The composite engineer responding to the unique design challenge has a number of variables at their disposal, each of these inputs has an impact on performance.
1. What kind of fiber reinforcement?
• High quality woven directional fibre or chop strand mat?
• Glass fibre, natural fibre or is there a more specific challenge perhaps requiring Kevlar (impact resistance) or Carbon fibre
• Quantity (thickness) of the fibre reinforcement.
• Orientation of the fibre (this will typically be designed to change from one layer to the next).
2. What manufacturing method?
A low-tech manufacturing technique can only every deliver an inconsistent product. Variations in resin to reinforcement ratio has a large impact on strength, weight and fire retardant qualities.
• Chopper gun – low quality non-structural (truck bonnets, swimming pools).
• Wet layup (hand consolidation) – prone to inconsistency due to high individual influence.
• Vacuum infused – high quality, consistent result with predictable resin ratio.
• Pre-impregnated cloth cured with pressure and heat (autoclave) – Aerospace quality.
3. What resin system (binder).
• Vinyl ester
• Fire retardant systems
Each one of these choices has a large and inter-dependent impact on the end result.
The growth of advanced composites in such diverse industries such as construction, defence, infrastructure and aerospace gives some indication as to how empowering composites can be to the design process. As more and more industries embrace the benefits of composites, the price of the inputs are dropping and the skill level in manufacturing is increasing.
And while it is possible to create complex forms in concrete and steel, they are often either prohibitively expensive or incredibly difficult to achieve, or both. So, when considerations of the cost of installation, overall environmental footprint and compliance when compared to other systems (steel, concrete etc) then this new technology is due to play an integral role in architectural design and building construction for decades to come.