On Thursday evening, I gave a short talk at a meeting of Advantage West Midlands Innovation and Technology Council and their materials constituency. I have to admit that I didn’t make a very good job of it. The week had been busy and I hadn’t prepared sufficiently - and then the travel from an afternoon meeting in London to the hotel venue in the middle of Birmingham went badly. I ended up arriving with about 5 minutes to spare and just wasn’t ready. In partial apology to those who heard me, this post is an attempt to frame the argument more coherently!!

Advanced Materials is an interesting subject for any meeting. It usually ends up with a large constituency of fibre reinforced composite producers seeking the latest defence or aerospace contract. However, there is a growing awareness that materials can be "advanced" outside this restricted application set and that it is the requirement of satisfying a complex specification that makes a material advanced.

That said, materials selection has historically been an interesting area to rationalise. We have to cover all the way from forensic evaluation to archaeological timescales. We take for granted that some materials and applications are intertwined, but the truth is that choice of a material for a specific application is now bounded as much by inertia as scientific understanding. There is a hierarchy of selection criteria than can be rationalised, but evidence suggests that it doesn’t always go according to plan.

The first criterion is performance. This is primarily about basic materials parameters; modulus, strength and weight are what usually get evaluated. This presupposes that we know what performance the application requires and can cover all the aspects. For example, we traditionally make drinking containers out of glass – indeed the material and the application name have become synonymous. But is a high modulus, brittle material with high optical clarity, reasonable high temperature performance and low permeability to water really the right choice? “Glasses” can be made out of polymers, ceramics, metals and even wood (with suitable internal surface coatings) – why is the default selection glass?

Next comes price and availability. Although ultimately performance is use is what drives selection, it is inevitably a compromise between the best performance and the best value performance. And it is in the fourth criterion that compromises in materials selection based on upfront price usually become apparent!!!

Third, but linked to this is processability – you have to be able to make the product or component cost effectively. This is one reason why polymers have made the inroads they have into many applications over the last 80 or so years – they are cheap and simple to fabricate. Interestingly, cheap here is as much about energy costs as anything else.

Having taken care of making the product cost-effectively, next comes lifetime performance. I am actually old enough to remember when cars broke down a lot, or domestic appliances needed to be taken back to the shop with sickening regularity. When I started in industry a long time ago, my then employer was evaluating the fatigue performance of steels used in offshore structures – though it already had a number at the time!! The truth is that we used to assume that materials properties where time independent and that the environment they worked in would not affect their properties. In this respect, some of the findings and recommendations of the Materials for Energy Strategic Research Agenda are interesting.

Although many materials selection processes stop there, any application that goes anywhere near a consumer can add “design” at this point. Those of you who follow this blog will know that I am a great fan of Sebastian Conran’s “Design Equation” – mentioned before. Since we are all consumers, we know that buying is not a logical process. Choices are made based on “soft” issues like fashion or previous experience or recommendation. The components of Sebastian’s numerator try to capture the complexity of this set of issues, whilst the denominator captures the cost aspect and the resulting fraction captures the cost-benefit balance.

Finally, for the moment at least, we need to take account of the environmental impact. It will not be long before we have to account for the imbedded energy or carbon of a material we are selecting for a specific use – not just its provenance, but its future – how will we re-use, recycle or dispose of a material once it has served it (first) useful life? At the moment there is no validated way of determining the imbedded energy of a material, since different routes to its current state may be very different, but unless we start to work out how we would determine this value, we run the risk of doing to the fabric of our planet what we seemed to have done to its atmosphere – render it unsustainable. As part of the Materials Innovation and Growth Team, the industry itself identified and started to address this issue, but it requires more effort – will you join?

David