CompositesWorld
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NEWS 31 CompositesWorld.com to the most promising layups," Assaker says, adding that the current allowables method- ology, which is basically 'black metal' design, might be sufficient for conventional layups (0°/±45°/90°), but increasing the perfor- mance of composite structures might require novel designs, such as asymmetric laminates with low angles (20°, 30°, etc.) and different manufacturing techniques, such as steered fibers. "Determining the performance of NTLs will become increasingly important." A matter of semantics? Rousseau says the consensus among his peers at the American Society of Compos- ites 31 st Technical Conference (Sept. 19-22, Williamsburg, VA, US) was "there is no use for VA in certification." He concedes, "we do believe it is very useful in the pre-design and design development process. For allowables, you simply cannot simulate the statistical data required." Assaker believes that VA can capture more variability than BBA: "BBA uses three batches of material. We do the same by randomly picking different resin and fiber properties within the range of values given in the material specification and/or lamina physical test data. erefore, we can test three batches or 100 simply by changing one variable in the software from 3 to 100. e range in data was already input at the beginning. e only change is computer crunching time." In the future, he sees the possibility to input all of the data from an OEM's receiving procedures — e.g., testing and/or review to verify that incoming materials comply with OEM material spec- ifications — into the model. is would integrate the power of Big Data, which is already used by manufacturers to reduce variability, off-spec parts and waste. Assaker contends, "e argument between virtual and physical testing in the development of allowables has been presented as a false choice between one or the other. VA is interpreted as using simu- lation results directly in the production of design allowables for certification. We see certification as separate. What we're proposing is simula- tion to help reduce the number of allowables tests they need to do." Rousseau agrees, "e best way to use the simulation/VA tools is as a more efficient way to design a test program. I see these as complementary to the traditional allowables methods, not competitive." Assaker says experts like Rousseau can play a key role in helping to refine VA and move it forward to make the allowables process more informative and efficient. BBA vs. VA Testing We create chemistry that makes countless products love added performance BASF high performance polyurethanes and engineering plastics bring extraordinary innovation to everyday life. These breakthrough materials make vehicles lighter and more fuel efficient, buildings and infrastructure more durable and energy efficient, manufacturing process and products more efficient, and a myriad of consumer dramatically better. Big ideas. Small environmental footprint. Because at BASF, we create chemistry. www.performance-materials.basf.us CW senior editor Ginger Gardiner has an engineering/materials background and more than 20 years of experience in the composites industry. ginger@compositesworld.com Read this article online | short.compositesworld.com/PvsVT