Understanding materials in D&T


A flurry of tweets asking what pupils should learn about materials in D&T has prompted this blog. To my mind the understanding of materials has a central place in D&T. We live, literally as reminded by Madonna, in a material world. So to understand and perhaps take part in conceiving and constructing such a world what might pupils need to know? Can we identify a set of ‘BIG’ ideas that underpin pupil understanding of materials? I believe we can. The first BIG idea is that of ‘property’ – the features of a material or substance that distinguish it from other materials and substances and which define the way that material behaves. The second BIG idea as far a D&T is concerned is that we can divide the properties of a particular material into two main categories: the intrinsic properties of that material and the working properties of that material. The former are concerned with what that material is like and the latter with how we can apply tools and processes to change the form of a piece of that material. The intrinsic properties can be further divided in categories such as mechanical, electrical, optical, thermal, chemical and a broad set of aesthetic qualities. These properties can be applied to all and any materials but sometimes the form of the material can affect the way the properties play out. In the case of textiles the behaviour of a particular piece of fabric will depend on the intrinsic properties of the material, the tightness with which the fibers have been spun into a yarn and the looseness or tightness of the weave used to produce the fabric from the yarn. So this is quite tricky territory. In D&T we would want pupils to chose the material they think is most appropriate for the design they are envisaging. Clearly they will need to take into account the intrinsic properties of possible materials and also consider whether they themselves have the necessary skill, tools and equipment to process the material into the required form. Overlaid on this of course will be the cost or purchasing the material – affordability is important. But the choice requires further considerations. Where does the material come from, by what means is it obtained and what is the carbon footprint of this acquisition? If the material is non-renewable it will be important to consider the longevity of the material. How long will it be available for if it is used up and not recycled or up-cycled? Whilst such considerations may be beyond the scope of pupils’ personal material choice in school they should feature highly in any critique pupils make of the choices made by professional designers and engineers. So the third BIG idea is that in choosing a material, designers and engineers have to make a judgment as to which is the most appropriate using criteria concerned with properties, cost, source, footprint and longevity and that often there has to be trade offs between these sets of criteria. So, for example, I might choose material A as opposed to that material B because although A is less strong (so I have to make the part thicker) it is much easier to recycle. Often designers and engineers (and pupils) use precedent to simplify this decision making process. In a similar design this material worked well so I’ll use that too. Whilst this yields a quick and apparently successful result as the future unfolds the impact and significance of source, footprint and longevity on the decision may well change and precedent might not be the best way of approaching the decision. And as the future unfolds nanotechnology will become ever more important in developing materials with particular and unusual properties. The properties of such materials will depend not so much on the material used but on the nanostructure by which that material is built. This is heady stuff which runs counter to our teaching of the first and second BIG ideas and is probably best left until pupils are in Key Stage 4. So if the above represents the BIG ideas about materials we want to teach pupils in D&T the question is “What’s a good way to do this across KS3 and KS4?” How can we use teaching about these BIG ideas to develop both pupils’ technological capability as designers and makers in their own right AND their technological perspective through which they can take a position on the way society uses the materials at its disposal. I’ll leave the last word to Mark Miodownik, Director of the Institute of Making at University College London

Making is not just an economic activity, it is the equal of literature, performance or mathematics as a form of human expression. By eschewing material knowledge we cease to understand the world around us.

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4 thoughts on “Understanding materials in D&T

  1. Pingback: Where does D&T fit into Nick Gibb’s Social Justice Case for an Academic Curriculum? | David and Torben for D&T

  2. Hi Tim
    As always your considered response has made me think. I didn’t know of the Agency of Design website but it is certainly well worth a visit. And of course underpinning the thinking here is the BIG idea of Product Life Cycle Analysis linked to linear and circular economy models.
    You are right to bring up the importance of teaching technical knowledge and understanding and this is a strong point Frank Banks and I make in our STEM book.
    See http://www.routledge.com/books/details/9780415675314/
    There is a need for pupils to think about properties in both qualitative and quantitative ways. Clearly we start with qualitative – what is this material like with regard to a range of properties, then we can ask pupils to make simple comparisons hence moving to a semi-quantitative approach. It’s easy to organize small pieces of sheet metal into an order of hardness, for instance, by using simple scratch testing, an order of density by simply weighing pieces the same size, stiffness experiencing how hard they are to bend etc. This is probably all that needs to be done at KS3 and sets the scene for more demanding quantitative work at KS4 where pupils can measure and calculate some properties and use data tables for others. The distinction between stiffness and strength is always a challenge but worth establishing – stiffness is concerned with how difficult/easy a material is to stretch or bend whilst strength is concerned with how difficult/easy it is to break. You can tease the brighter ones by asking, “Ok if strength and stiffness are different how come they have the same units?” And of course establishing why particular properties have the units they do is important to understand.
    Your tale of misunderstanding with regard to tempering carbon steel for screwdriver blades was very interesting and made me think about the screwdriver ‘project’. I must admit I’ve never been that much of a fan of pupils making screwdrivers but your comment made me reconsider. There are all sorts of interesting design decisions wrapped up in a screw driver – the size of the blade – how does this relate to sizes of available screws, the length and thickness of the shaft – some screw drivers have very short shafts, some very long, the shape and material of the handle. To my mind having suffered blisters on the palm of my hand when putting up lots of shelves the nature of the handle is particularly important. Then I remembered the historical dimension; there was a time when machine screws and nuts had to be matched pairs because the nut from one screw wouldn’t necessarily fit a different screw. The advent and importance of accurately reproducible screw threads is told in a wonderful short book – One good turn – recommended reading for all D&T teachers and some great short pieces for pupils to read.
    Available at http://www.amazon.co.uk/One-Good-Turn-Natural-Screwdriver/dp/0743208501/ref=sr_1_8?s=books&ie=UTF8&qid=1435226247&sr=1-8&keywords=one+good+turn
    And then there is the difference between various screw types – why are screws for chipboard different from screws for ‘proper’ wood. And then there is the question of the difference between nails and screws – that they ‘work’ in a different way and hence are used for different purposes. If all this were combined into a screwdriver project I think the learning would be very rich, demanding and worthwhile and could well embrace the BIG ideas about materials.
    Recently the Teacher Development Trust published an interesting document Developing Great Teaching about the sort of in service that should be provided if we listen to the research findings about effective professional development.
    Available at http://tdtrust.org/about/dgt/
    D&T teachers should take note of this I think and use it to plan for the sort of cpd that has been so lacking recently.

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  3. I think the problem lies much deeper than the big ideas you outline. I agree entirely with your suggestion that teachers should be able to teach pupils about the environmental costs of materials so they can tread lightly in their designing but where is the accurate information in a form pupils can access? Material properties databases exist in the commercial sector but embedded in Product Lifecycle Management (PLM) software. Have you seen the Energy Trumps cards from the Agency of Design? Aiimed at the education sector they explain the energy needed to process the raw materials things are made from.
    http://www.agencyofdesign.co.uk/projects/designing-with-energy/

    You mention making the choice to use a material for its green credentials, accepting the part will have to be thicker. This assumes the pupil also understands how to work out how thick the part needs to be. Typically, pupils will draw a shape, make the part and see if it works. If so, everything is fine. If however, the part breaks during testing, they make it bigger. Empirical design has it’s place particularly when working at the boundaries of knowledge but most of the materials used in schools have been around a long time and there is a wealth of information available. Sadly most of the pupils leave school not knowing about stress, strain, Young’s modulus and how materials behave when forces are applied. Without this how can they design anything with confidence? There is every chance their designs might fail unexpectedly or have a Factor of Safety many times what is needed, wasting the precious resources you refer to.

    So why do pupils not know these things? With some notable exceptions the majority of teachers I encounter have very weak understanding of material properties and how processing changes them. Here is just one of many examples I could quote from the Facebook forums for D&T. In a forum for engineering, a teacher posted an explanation of a screwdriver she was getting the pupils to make and several other engineering teachers had posted encouragement asking for the scheme of work. I felt compelled to ask how well the finished screwdrivers performed as they were making them from mild steel. The teacher proudly replied they were hardening them. I replied saying that mild steel could not be hardened. The teacher replied with a link to the http://www.technologystudent.com entry correctly saying mild steel could be case hardened. What she didn’t understand was case hardening only affects a thin surface layer to resist wear and overall the screwdriver blade doesn’t have the toughness to resist bending and twisting. I responded with a link to the same website bu the entry for hardening and tempering carbon steel suggesting this was a more suitable material for the blade and correctly heat treated would offer both the wear resistance and toughness required.

    Over the last quarter of a century the funding for the initial training and professional development of D&T teachers has been cut to the bone. I explore this in a little more detail in a blog post on ‘Teacher Expertise in D&T’ here. https://tbrotherhood.wordpress.com/blog/

    I support your call for a greater awareness of the big ideas that will help sustain our planet but this must be matched by improving teachers technical understanding of the materials, processes and components. Unless this is tackled with great urgency instead of other countries copying our world leading position, they will address these issues and become the future leaders of technical and design education.

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