An international consortium led by the Stanford University composites pioneer Dr. Stephen Tsai has developed a new type of carbon-fiber composite. The thin-ply, bi-angle, noncrimp fabric, which uses a nonwoven fabric architecture, delivers more than three times the tensile strength of conventional woven carbon-fiber fabrics and resin infusion methods.
The consortium includes Stanford's Department of Aeronautics and Astronautics, Chomarat Textiles Industries, Advaero Technologies, NASA Marshall Space Flight Center, the composite component manufacturer VX Aerospace, and the aerospace carbon-fiber and composite materials maker Hexcel. Materials developed based on this technology will target industries that need lightweight, high-strength structures, especially aerospace manufacturing.
A new carbon-fiber composite material test sample made with Advaero's HVARTM resin infusion process has more than three times the pull strength of conventional carbon-fiber composites.
(Source: Advaero Technologies)
Greg Bowers, co-founder, president, and CEO of Advaero, told us his company has completed initial trials of the new composite. It is produced using Chomarat's newly developed 150 gsm bi-angle, noncrimp carbon fabric, which is infused with resin using Advaero's HVARTM (heated vacuum-assisted resin transfer molding) process. This process is more cost-effective than the energy-intensive high-pressure autoclave ovens conventionally used to produce carbon-fiber composites, Bowers says.
Dr. Ajit Kelkar, professor and chairman of nanoengineering at North Carolina A&T State University's Joint School of Nanoscience and Nanoengineering, co-invented HVARTM. "Typically, carbon-fiber composites for aerospace applications are very strong in one direction but weak in other directions," he told us. "To balance their strength, they have to be reinforced. That's why composites are manufactured with layers oriented in different directions stacked together. If you don't, the composites will warp and bend."
When I first read Jerry's post, I thought he was being a bit of a Luddite. But after re-reading the article, I think he may have some valid points. The key thing is that the test was a tensile-pull-to-failure test. That is not at all indicitave of how CF structures are stressed. If the fiber orientation is almost parallel to the pull test axis, of course it will yield better results compared to a woven or cross hatch layup. I would like to see a variety of comparative test-to-failure scenarios (axial twist, bending, compression, etc.) between this layup method and traditional woven layups. I'm not saying this design doesn't potentially have merit, but the test shown is not conclusive evidence of this technique's validity in real world utilization.
Great article, Ann. Are they able to quantify the tensile capacity (in psi or ksi) of this material versus that of conventional woven carbon fiber fabrics? Or is it too early to give a solid number? Also, does the higher tensile capacity place it in a different set of applications? A threefold increase is an amazing jump.
Again another bad PR piece. Nothing new here I can see as I've been doing this way for 35 yrs!! It's basic common sense among those who do it.
While these examples are mostly true, no one does them because they are not cost effective or just plain dumb!!
Anyone who uses woven CF just doesn't know enough to use it. CF is great only in tension, compression where it is very good. But only if it stays perfectally straight. If bent as a weave it becomes very expensive springs!! And just not much tension or compression strength in springs of CF. So why do it?
Anytime you see woven CF cloth the only reason it is there is CF hype as once woven, has less strength than FG done right at 10% of the cost of CF.
As for the resins we have many that do the same thing as the example. Selective examples like used are just a form of disinformation.
Thanks, Beth, great questions. The main issues of concern about CFR composites have been detecting failure. Whether this material addresses that problem remains to be seen. One could hypothesize that because its failure modes take longer to reach breaking point and are more spread out throughout the fabric because of its different structure, that those failures might be more visible, using the safety glass analogy. Regarding process, fewer layers to achieve the same strength imply it will be faster, as well as saving a great deal more energy.
I'll email my contacts at Advaero to see if they can address those questions.
Ann, This kind of development just underscores the fundamental need and desire for lighter but very strong materials. Research and new product development in this area is vital enabling technology moving ahead on so many fronts when it comes to more efficient designs. Thanks.
This nonwoven architecture seems like it would have some real potential. Would it address some of the issues you've been writing about in terms of the challenges and concerns around addressing composite failures when aircraft are in the field? Also, I'm wondering about what's involved in creating and supporting the manufacturing process for a material like this. It seems like an entirely new approach and I'm wondering what kind of hurdle that could be for companies already invested in tools and processes specifically designed to support the use of composite materials in their products.
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