Although composite materials have an established history in certain sectors, such as aerospace, marine and Formula 1, in others they are just beginning to make in-roads. If these materials are going to used more extensively in markets such as high volume automotive or construction the demand for testing them will mean a much greater throughput of tests will be required.
Paul Yeo is technical director at Composite Test & Evaluation (CTE), a testing firm based in Honiton near Exeter. Yeo started the firm six years ago when he realised the potential new markets that composite materials were moving into.
“I worked in AgustaWestland’s rotor blade development lab and saw an opportunity to set up my own test lab mirroring the work I did there, but for a wider range of customers,” he says. “At the time there were not many companies solely concentrating on non-metallic testing. We started with just one test frame carrying out static tests but we have grown and now the business is doing really well.”
Although CTE’s work at first was primarily aerospace related it now also includes, automotive, renewable energy, rail and the construction markets.
“We have added thermal analysis testing capability and fatigue testing to our portfolio,” Yeo explains. “There is a lot of demand for light weighting vehicles in the transport sector so high volume manufacturers can reduce emissions. There is also more construction based work, particularly in sectors such as rail.”
One of the company’s USPs is the Evaluation Service that it offers customers.
“At the moment it is used primarily by the aerospace market for first article inspections. We tear down a component and look to see how it has been laid up and look for any defects that may have arisen during the manufacturing process. Although NDT may show there is a void or delamination it can’t reveal what has caused it. We can say it was because there was a lack of pressure or that the delamination happened because there was a failure delivering the resin. It means we can give a more detailed examination about what those NDT defects are and then that helps our clients reduce scrap and re-work time.”
More confidence and capability
To grow the business Yeo needed to find a supplier of testing equipment. Although he was familiar with some established names in the market, Shimadzu was new to him.
“We wanted to improve our capability and capacity for all our customers and not have any risk of a complete service failure. Shimadzu were offering what turned out to be very good systems at a very good price for us as an end user.
“Because they were made in Japan I had some confidence in their quality but when I saw the machines being demonstrated in Germany I could see they were very well-built. They are very accurate and we have never had a problem getting them calibrated. Shimadzu delivered a good product and it has helped us to further the business. We also advised them on some of their software to help make improvements.”
So it turns out Yeo made a successful choice, despite his initial reservations.
“The first test frame was small but once we had confidence in the machine and could see Shimadzu were building their support base in the UK it was easier for us to approach them for any other requirements we needed.”
Yeo now has three Shimadzu test frames added to his original equipment.
“We do standard static tests on them. We also have a T slot bed on one Shimadzu machine that allows us to do structural testing of small scale components and more non-standard testing. The T slot helps us with various attachments so we can fixture these odd shaped parts to the machine. It gives us a lot more flexibility.”
As well as carrying out testing CTE also offers a Specimen Preparation service. Yeo comments: “Test results are only as good as the specimen. For one of our aerospace customers we cut all of their test specimens so they can concentrate on performing the tests and examining the results. We can create test coupons of very high quality and quickly with the Sharp and Tappin Composite Plate Saw equipment we have.”
The need for creating new test coupons is because of the evolving and diverse nature of composite materials themselves.
“The major benefit of composite materials is that each one can be slightly different. There are different resin systems and different fibres, so each resin/carbon fibre or glass fibre combination will behave slightly differently. It’s not just the new resins it’s also the latest weaves, stitching and fibres. Every time new developments occur it slightly changes the way the material will behave so it has to be tested again. Companies may complain that they have to keep re-testing composite materials but you have to if you are also going to benefit from the many advantages that they offer designers and manufactures.”
So how does Yeo see the future and the development of composites?
“The bulk of our work involves thermoset materials but more recently we have also been testing thermoplastics. We have been looking at how thermoplastics can be welded together because bonding them can be difficult. In theory thermoplastics have some great advantages. They are quicker and easier to mould and are more easily recyclable. Automotive companies particularly will be driving their development but it is early days and costs will need to come down.
“Another big advance is 3D weaving. There is a lot of work trying to improve the through thickness strength of composites. 3D weaving offers a solution, but it is expensive and limited in the sizes that can be made. It also takes a long time to set up the weaving process.”
Building bridges
Yeo says automotive OEMs are looking further into looking into using composite components for structural applications in vehicles but one of the biggest new markets he anticipates will be construction.
“Testing construction applications is obviously very different from something like aerospace, but those criteria still have to be met. With the introduction of high speed rail, structures like bridges are going to be required and there is the benefit that they can be built completely offsite in composites. In the construction industry getting people to agree to use new materials can be difficult so our testing gives them the confidence that they can work.”
However, it’s not only reliable and accurate hardware such as the Shimadzu testing frames that Yeo uses if demand and throughput rates are going to be achieved. There is also more work to be done on the software front and testing processes themselves.
“Software has a big part to play in easing the processing of the data and features such as live calculation so you can see what is happening during testing before you actually break the coupon. There also needs to be improvements in strain measurement. There are some optical systems for measuring strain. They meet some standards but not all. They need to be developed so that they can be used inside and outside of an oven and measure both sides of the specimen accurately with the minimum amount of set-up. That would improve turnaround times and reduce costs.”
