The UK SUSTCOMP collaborative project has brought together industrial partners and researchers to develop a large prototype diaphragm-forming machine capable of operating at high production speeds.
‘More and more, sustainability is becoming a key aspect for the industry’, explains Dr Matthew Turner, Composites Engineer with project managers Europrojects LTTC Ltd (EPL), an independent consultancy specialising in application of thermoplastic composites. ‘Composite components offer light weight and user fuel efficiency but traditional composites are not recyclable. That is where thermoplastic composites win out. You don’t have to waste precious resources on manufacturing something just once and then burying it or burning it. You can re-use it over and over again.’
As well as having excellent mechanical properties, thermoplastic composites are more recyclable than thermosets and no VOCs are given off during manufacture. However until now production processes such as vacuum bagging have been very slow and labour intensive and the main alternative, compression moulding, requires expensive tooling.
The new diaphragm forming process, developed with support from the Sustainable Technologies Initiative will enable more producers to switch to the latest thermoplastic composite materials. Moulding and heating are carried out between two thin silicone rubber diaphragms, producing high quality mouldings with inexpensive tools and greatly reduced energy consumption.
‘We wanted to speed the whole process up and by doing that increase sustainability of the production process,’ says Dr Turner. ‘Our prototype machine is 16 times quicker than the vacuum bagging process, taking just 15 minutes instead of four hours or more to produce typical FRP components. Energy usage is tiny in comparison because you only heat the composite material instead of the composite and the tooling.’
Trials showed that production costs are already competitive with hand lay-up methods and researchers have identified how production rates could be increased by up to 500% in future versions, making the process even more competitive. Tooling costs are much lower than other processes, a particular attraction for manufacturers making wide ranges of components.
A comprehensive Life Cycle Analysis carried out by Queen Mary University London demonstrated that the process is highly sustainable, has zero emissions of solvents and low labour requirements. Investigations confirmed that waste can be recycled into thermoplastic sheet and as much as 20% can be re-used in new products with no loss of performance. Case studies were carried out on a lid for oil storage tanks and a prototype wind turbine blade section, designed to be lighter, stronger and, more importantly, faster to produce than traditional blades.
The results could have important implications for industries that are major users of FRP products. Thermoplastics are mechanically tough and durable, and less brittle than thermoset materials, making them ideally suited for applications ranging from impact-resistant stone guards under rally cars and trains to bullet-proof vests that are more comfortable to wear. In the marine industry, fibre reinforced thermoplastics will provide an alternative to traditional hand lay-up methods while making it easier to meet health and safety requirements in boat yards by eliminating the need to contain VOC emissions. In the construction industry applications include lightweight scaffold decks and concrete shuttering.
‘Our collaboration worked very well and future prospects look good,’ says Dr Turner. ‘The industrial partners are very positive about the results and we are now discussing the options for continued research and future manufacture.’
The Sustainable Technologies Initiative is a programme of collaborative research and development aimed at improving the sustainability of UK businesses. The aim has been to maintain high levels of economic growth and employment while protecting the environment, making better use of natural resources and working for the good of society as a whole. Companies have been encouraged to work with the science base to develop and adopt new sustainable technologies.
The STI programme, which is now closed for new applications, has been sponsored by the Department of Trade and Industry (DTI), the Engineering and Physical Sciences Research Council (EPSRC), the Department of Environment, Food and Rural Affairs (Defra), the Biotechnology and Biological Sciences Research Council (BBSRC) and the Economic and Social Research Council (ESRC).
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