Case Study

Streamlining the visualization of composite analysis results

ATA Engineering (Femap)

Use of the Femap API lowers the cost of composite analysis for the bottom-line benefit of both ATA and its customers

Aerospace means composites

For more than thirty years, ATA Engineering, Inc., (ATA) has been providing analysis- and test-driven design solutions for structural, mechanical, electromechanical and aerospace products. The company has worked on a wide range of projects, including amusement park rides, biomedical devices and electronics components. The majority of its work has been within the aerospace industry for customers including Orbital Sciences, Lockheed Martin Space Systems, Pratt & Whitney, NASA, Jet Propulsion Laboratory, Air Force Research Laboratory and General Atomics.

ATA’s work for the aerospace industry increasingly involves the analysis of composite structures, as these materials are lightweight and strong. However, this analysis is much more involved and more challenging to process than that of metallic structures, due to their more complex failure modes. “Compared to other materials, there are many more ways in which a composite structure can fail,” explains Charles Webber, an engineer at ATA. This had made composite analysis more time-consuming for ATA and therefore more expensive for its customers.

“ATA must often analyze interlaminar shear stress for the core material, a critical component in analyzing the strength of a composite structure,” says Webber, “and this can be very laborintensive.” To evaluate this, the analyst selects each layup one at a time, manually changes the output vector to find the core ply, documents the results for that particular core shear stress, and repeats the process – for potentially hundreds of layups. “This was very time-consuming,” Webber states. After realizing that he would need to spend about three days doing this for one customer’s analysis, he figured out a way to automate the process.

No formal training

This was feasible, Webber notes, because he was using the Femap™ FEA pre- and post-processor from Siemens PLM Software. “Our customer requires Femap, so I had been using it for about a year,” Webber explains. “I had no problem learning it, and I quickly grew to like a lot of the features.”

One of the features that Webber likes is the Femap application programming interface (API), which he found easy to learn. “I didn’t need a training class,” he notes. “This is a strong point for Femap. I was able to teach myself just by using the documentation and looking at the examples.With Femap, you can pick it up as you work with the program.” The intuitive nature of the Femap API, combined with the fact that it supports Visual Basic, made Webber feel confident that he could automate the determination of core shear stresses.

Direct access to results data

Another feature of Femap that was important in this project was the software’s open architecture. “This makes it easy to interact with your model and results data,” Webber explains. “When I use the Femap API, I get the data in its native form from the solver.”

This was central to the core shear stress application because it allowed Webber to create a new output vector and plot the results in a contour plot.Where previously he had simply recorded stress values for each layup, the application he wrote gives the added benefit of being able to visualize the stress level, rather than just have it represented by a number. “The beauty of the Femap API is that I get to manipulate the raw data, and when I’m done manipulating it, I can still keep it within Femap and use the software’s visualization functionality.” The new output vector can also be used in conjunction with Femap’s Data Table for quick summaries.

The bottom line

Webber estimates that it took him and a colleague at ATA, Ali Gokce, eight to ten hours to write a core shear stress application that sorted and collected all of the core shear stresses onto a new output vector. This was the most complicated application they had attempted at that point with the Femap API. Webber believes that someone with more experience could have written it in less than four hours. The Femap API macros have been such a powerful way of extending and customizing Femap that macros are often shared between project team members or organizations.

Now that the custom program has been created, ATA can look at interlaminar shear stresses much more efficiently; the time it takes to complete the formerly labor-intensive task is reduced to a few seconds or minutes with the “push-button” tool. Using the Femap API, a relatively novice user wrote a program that lowers the cost of composite analysis for the bottom-line benefit of both ATA and its customers.

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