What information are the tests missing?
Well, one example is an ASTM standard test that is used to certify parts with solvent resistivity. When you take a composite panel and submerge it in skydrol at 70 C for a certain time, take it out, rinse it, dry it and test the mechanical properties, you discover you’ve lost X amount or the material has swelled by so much. It’s a specific test, but it’s not realistic test. Airplane builders are discovering that if you take a composite part, put it under tension and then submerge it under skydrol, the whole thing fails in a fraction of the time. Right now that’s not an official test, but it’s a very realistic test because at some point airplane parts are under tension or being loaded.
Is aerospace focused on invention or perfection?
Right now, they’re struggling with the materials that are there. Like everyone else in composites, the aerospace industry is struggling with the fact that on one end you have fiber and on the other there is the resin and these two things just don’t like each other. That’s just a fact. People have become handy over the years, playing around with processing and sizing to make the fiber like the resin or vice versa. But all of this, in my opinion, is poor man’s approach to get something that is semi-workable. As a result, it’s a big push to design a fiber and resin from the same chemistry so they inherently like each other.
Where is there the greatest potential for composite growth?
It is an interesting question in the sense that if you ask what is driving the industry, an obvious answer is fuel prices driving to lighter cars and electric cars. To make those plausible, auto manufacturers have to cut weight, so composites a good thing. I’d say I see the most potential within transportation in general, but also think designers have a big impact on this as well. Designers look to see what they can make/design and it’s all about what they feel people want, at the end of the day.
Where is there room for improvement within composites?
When a company purchases an all-composite aircraft, they ideally want it to fly for at least 30 years. I’m not confident that we understand composites properties enough to guarantee that it will work that long, especially if you think about fatigue properties. In general, there is a large gap between the fiber and resins. Toughness, fiber adhesion, solvent resistivity and temperature use are all characteristics that need to be improved. There are also gaps that need to be filled in relation to fatigue under use, fatigue under solvent exposure, repairability and property characteristics after impact. Right now, those are the major show stoppers that keep composites from become a real “adult material.”