​071116 – Composites – London

BMW i3 i8

A recent article in the FT praised the uptake of composites, especially carbon fibre, as a material to be used for mass-produced cars. Both the author and reader’s comments were enthusiastic for the wide spread application of composites for mass production. The planet supports 8 billion people and is already carrying at least 3 billion, possibly 6 billion, too many. Each of these would like a car. Many in the west own more than one. It is estimated that the Chinese alone will buy 40 million cars by 2020. Cars are multiple reoccurring buys, car manufacturers benefit from maximising this reoccurring purchase. Vehicle obsolescence increases the number of reoccurring purchases. Obsolescence in the car industry can be as fickle as colour, style or the addition of some unnecessary new electronic gadget. Style generated obsolescence is key to mass-market consumerism. The landfill sites are full, the oceans adrift with acres of discarded plastic. When the carbon fibre car body replaces the plastic drink bottle where will we throw the waste? The FT article, the author and all of the readers comments were oblivious to the fact that man pollutes by the decisions he makes at the point of manufacture.

To cut car emissions manufacturers are keen to reduce a cars weight. Electric cars are heavy due to the batteries carried. Hybrid cars are heavier still as they carry two power sources, battery packs and fuel storage. This additional weight is partially offset by reduction in body shell weight and carbon fibre is a proposed alternative. The BMW i3 and i8 are beautiful and sophisticated pieces of engineering design. They have the wow factor that will provide a short-term lift in sales but they are simultaneously examples of irresponsible industrial design at a corporate level.

Carbon Fibre

Carbon fibre is a unique material. Its strength to weight ratio is many multiples higher than steel or aluminium. It can be moulded into many complex forms essential for efficiently distributing loads through highly stressed junctions and intersections. Carbon fibre’s place in Formula One or the aircraft industry is well earned but as a medium of mass production it is an inappropriate material.

Carbon fibre consumes 14 times the amount of energy required to make steel. More than 90% of the energy needed to manufacture carbon fibre composites is consumed in making the carbon fibre itself. 90% of carbon fibre manufacture is derived from polyacrylonitrile made from acrylonitrile, which is derived from the commodity chemicals propylene and ammonia. The process of making carbon fibre requires multiple ovens used in sequence. The first two ovens are at temperatures of 200-300 degrees C but carbonization is achieved by putting the fibres through another series of ovens ranging in temperatures from 700-800 degrees C, then 1200-1500 degrees C and finally 3450-4500 degrees C. Alongside the energy intensive heat sequence is the chemical washing, doping, catalyst forming, cleaning this with acids and ammonia. Some of the chemicals used throughout the process include dimethyl sulfoxide, dimethyl acetamide or dimethyl formamide, zinc chloride and rhodan salt, itaconic acid, sulfur dioxide acid, sulfuric acid or methylacrylic acid. These are all highly toxic pollutants that the FT article is promoting if carbon fibre is mass-produced.

At end of use carbon fibre is even more problematic as it does not biodegrade or photodegrade. – EVER – it will sit in landfill for millenniums. Carbon fibre cannot in anyway be usefully recycled. There are two ways to re-use carbon fibre one of which involves burning without oxygen (pyrolysis), but this is an intensive use of energy and produces a brittle material. The second is shredding and reusing the by-product as fill or aggregate. In both scenarios it is more expensive to recycle carbon fibre than produce it from virgin material and the recycled material is severely downgraded and has very little use, quality or properties of the original composite material.

Molluscs

Abalone is the name of a group of large sea snails or molluscs. The shell is made of nacre a composite. Nacre is composed of hexagon platelets of aragonite, calcium carbonate (chalk) glued together with proteins and polysaccharides (sugars) to form elastic biopolymers. Abalone is twice as strong as any known ceramic. Its layered composite structure prevents shearing and provides compressive and tensile strength. This shell material deforms under stress and behaves like a metal. Abalone is an accumulative secreted medium a process similar to 3D printing and this technique is perfect for fabricating complex forms. 

Nacre like all of nature’s products is manufactured at ambient temperature using readily available non life threatening materials, here sugar and chalk. 

Nature has an ordered hierarchical structure, weaving from the atomic level to the macroscopic. This repetition is applied to all scales and provides the materials unique strength.

Structures built from a molecular level up have an inherent logic that dictates what bonds to what and how. This forms a pre-coded system of self-assembly.

This coding allows nature to work with templates that are site and condition specific. It builds exactly what it needs to the specification needed. There is no waste of either time or material.

At the end of its life the Abalone returns all it has used back to the sea. Its production cycle is fully cradle to cradle.

Material scientists are still unable to replicate the process of growing perfect crystalline structures and even further away from them being applied to mass production but the direction of future production is clear. The complex forms that can be constructed from secreted natural mediums will be far superior to processed sheet materials or toxic chemical moulds.

Aluminium

Aluminium is approximately 5 times more energy intensive than steel to produce although this only adds 15% to the cost of production over steel. Car manufacturing in aluminium requires additional tooling with increased complexity throughout the production process and this adds a total of 60%, including raw material production, over the cost of producing steel cars. However aluminium is 100% recyclable, it does not downgrade through the recycling process and uses 95% less energy to recycle than to produce from bauxite. Aluminium also weighs a third of steel. Complex shell moulding and bonding techniques can provide all of the protection and crumple zones required in a modern car. Aluminium can also be 3D printed to create complex crumple zones. There are many advantages in using aluminium for mass production including, availability, lightweight, corrosion resistance and the ability to recycle without downgrading. The additional cost of aluminium over steel is offset by efficient life cycle use and as aluminium an inherent high raw commodity value at the point of recycling.

Until we are able to understand how to build cars in a similar way that nature constructs the mollusc, from the molecular level up all at ambient temperature, aluminium is the transition medium of choice to be used for lighter mass produced cars just as gas is the transition medium as we move from coal to solar.

The Surrogate Twin.