Made to measure…Delaminations

Who are you?: Osman Ajmal

What is your role?: PhD Researcher

What is your work about?: Locating and measuring the growth of embedded delaminations in composite materials.

I beg your pardon?: Delaminations are one of the more prevalent forms of defects in composite materials such as Fibre Reinforced Polymers (FRPs). Non-Destructive Evaluation (NDE) is used to determine the position and size of delaminations during testing.

OK. Why?: FRPs are used in a wide variety of industries. They have applications as components of cars, aeroplanes, spacecraft and even sporting goods! By understanding how these defects in structural elements behave under different loading scenarios, these materials can be better tailored for different applications.

And?: My work compares existing and novel methods to detect these defects. Figure 1a is a finite element model of a typical specimen with an embedded defect, whilst Figure 1b shows a typical output from the real specimen, monitored by Digital Image Correlation (DIC).  Analysis of the DIC data gives, in this case, longitudinal surface strains which can be used to detect the presence of delaminations.

dic.png

Figure 1: Longitudinal strain contours of composite laminate specimen with an embedded square shaped artificial delamination in three point bending. (a) Finite Element Modelling (b) Digital Image Correlation

So what?: By comparing different NDE techniques to each other and to FEA, my work aims to determine the “resolution” of the different techniques. This is done by comparing the results of different techniques for the testing of the same structural elements and the same loading scenarios. By using artificial inserts, model defects can be created during the manufacturing process. During testing, these defects can be monitored: because the size of the delamination is known, the NDE technique can be assessed against what it   should detect, and if possible calibrated accordingly.

Final thought: The wide range of readily applicable NDE techniques are literally ‘made to measure’ defects in structural elements. It is important to determine how well they do this for delaminations in the composites used in modern cars, aeroplanes, ships and all the rest.

 

Advertisements

Made to Measure…Microscopy

Who are you? Rebecca Tung
What is your role? Undergraduate Medical Engineer on industrial placement in the Microstructural Studies Unit at the University of Surrey
What is your work about? I help to prepare and characterise materials using a variety of techniques, predominantly scanning electron microscopy based techniques.

I beg your pardon? Materials can be examined in a scanning electron microscope (SEM), which produces an electron image, to reveal microstructure and topography. In addition, the chemical composition of the material may be analysed which can help to determine the properties of a material.

What is a SEM? Scanning electron microscopes use a beam of accelerated electrons as a source of ‘illumination’. Electron microscopy offers a much higher spatial resolution than light microscopy and can reveal either microstructure or surface topography. When the beam interacts with the sample surface, some complex physical processes occur. This results in the emission of secondary electrons, backscattered electrons as well as X-rays. The detection of these three signals enables: (i) imaging of the surface topography, (ii) imaging of the microstructure and (iii) measuring the chemical composition. In the micrographs below, the difference between the detection of backscattered electrons and secondary electrons can be seen. Figure 1 shows the same Vickers hardness indent in a brittle material imaged with the two types of emitted electron. The behaviour of the low energy secondary electrons (Figure 1a) and high-energy backscattered electrons (Figure 1b), along with appropriate electron detectors, gives different information about the specimen.

Microscopy

Figure 1 – Comparison of Scanning Electron Microscopy modes: a) secondary electron image (the bright white areas suggest ‘charging’) and b) back scattered electron image.

And? Analysis of a material with a SEM offers not only increased resolution (therefore higher useful magnification) but the benefits of studying any combination of topography, microstructure and chemistry. Modern microscopes have multiple electron detectors that give different combinations and emphasis of information. Other possibilities include variable pressure microscopy which enables wet specimens to be studied and a focused ion beam capability which enables specimens to be sectioned and studied in 3D.

So what? The characterisation of engineering materials is essential for the goal of understanding microstructure-property-processing relationships. The SEM is arguably the most flexible technique that contributes to this goal.

Final Thought: SEM offers a variety of analytical techniques, which makes it a versatile tool for characterisation of materials. The capabilities of the JEOL 7100F SEM, at the University of Surrey, which is my favourite instrument, make it suitable for studying the whole range of engineering materials—it really is an instrument that is Made 2 Measure!

 

Made to Measure…Waste

Who are you?: Dr Jade-Ashlee Cox.

What is your role?: Currently a Senior Consultant at Ricardo Energy & Environment. Formerly I was an EngD Researcher on the University of Surrey’s, SEES programme, sponsored by Surrey County Council.

What is your work about?:A decision making framework for the sustainable management of household waste.

I beg your pardon?: Every week we throw away food, packaging, things that we’re done with – waste. But is the stuff that makes its way into out bins really waste? Our consumer goods, clothing, food and everything that we trade, requires resources to be grown and manufactured as well as energy, water and time. The term ‘waste’ has long been associated with disposal, and this might be part of the problem, as only 44% of household waste in the UK is recycled. Yet, if we were to think of household waste as a resource, it may be possible to extract its ‘value’. Items that householders no longer require should not simply be discarded of as waste, but instead should be appreciated for the inherent value they possess and the new products they can become. However, implementing this paradigm is complicated by the variety of different materials in the waste stream, and the number of stakeholders responsible for its management. A central theme of the work presented in this thesis is the paradigm shift ‘From Waste to Resource’.

Why?: There are two key issues that need to be addressed. Firstly, we need to understand what is present in the resource stream, and in what quantities. This then allows waste managers to make informed choices about collection strategies and investment in reprocessing infrastructure. Not all constituents of the resource stream will be present in economically viable quantities – at least not in one collection authority. Sometimes it is necessary to pool resources with other councils, if you know how much of something you have got. Secondly, in some cases there is ‘more than one way to skin a cat’. For most materials that we would want to deal with there are multiple options, and the inevitable default of landfill or incineration. These different reprocessing options will have their own costs, benefits and implications: is it better to ship something across overseas to the most efficient reprocessing plant, or keep it local but get a minimal return? This is not always a straightforward question to answer.

And?: This is important both for issues of resource security and sustainability. Indeed, whilst the times of ‘make do and mend’ can appear to be in the past, there is a great deal of interest in reusing and recovering material resources, especially if components or assemblages can be refurbished or ‘upcycled’. This research has developed a decision-making tool, which can enable local authorities to assess the best way of managing their household ‘waste’. This takes the user through the identification and quantification of the materials of interest, the determination of viable treatment options, and an options appraisal.

Waste supply chain-1

Figure 1 – Complexity of the waste supply chain network. Direct relationships are represented by solid green lines. The dotted lines represent future relationships and solid black lines represents influences. (After Cox and Jesson, 2015.  Artwork produced by Materials World from an orginal diagram).

So what?: By understanding the composition, amount and value of ‘waste’ available to them, local authorities can take a more proactive approach in the ‘Waste Supply Chain’ to prevent the implementation of ‘sub-optimal’ management practices and the loss of valuable resources.

Final Thought: Using something once and letting it end up in landfill is the real waste. We can all do our bit at home like taking our old clothes to the local charity shop, but that will only take us so far. Crucially, we need to make sure that our resources stay out of landfill and remain in the cycle.

If you’d like to read more about assessing the resource stream, you might like to check out our award winning paper (ICE Telford Premium, 2016), here, for free.