Designing, simulating and optimizing a static test setup for carbon fiber brake calipers 66 percent faster with reduced costs

Realizing lighter, greener vehicle components

Transitioning from internal combustion engines (ICEs) to electric vehicles provides significant design and development opportunities for the powertrain and creates opportunities for innovating other components.

For instance, the difference in the braking characteristics of the two types of vehicles necessitates a review of the brake caliper design to ensure effective performance, creating the opportunity to consider alternative materials such as carbon fiber.

One advantage of using carbon fiber is the reduction in weight. The lighter a vehicle, the less power is needed to propel it, and the more environmentally friendly the vehicle becomes.

Additionally, the materials used to make the carbon fiber composites can be acquired from recycled sources, increasing the green credentials of the vehicle.

To investigate this further, an initial study was created as part of the transnational M-ERA.NET research project CARBOBRAKE (grant number 889149) across Austria, Belgium and Spain. M-ERA.NET is a European Union (EU) funded network that has been established to support and increase the coordination of European research programs and related funding in materials science and engineering. Andreas Kapshammer, researcher at the Johannes Kepler University Linz Institute of Polymer Product Engineering (JKU Linz), undertook a proof-of-concept project to investigate the material characterization and modeling as well as the development of a static test setup. Within the scope of the CARBOBRAKE project, a thick-walled, carbon fiber reinforced brake caliper prototype is being developed for motorcycles.

Simulating fiber orientation

Kapshammer explains that Simcenter™ Multimech™ software was vital to the development of the static test setup. “It was clear from the beginning that we needed an integrative simulation workflow in the design phase to ensure we understood the mechanical behavior in detail,” says Kapshammer. “The mechanical performance of carbon fiber composites is dependent on the orientation of the fibers before they are cured into a solid resin. So when we design the component, we can only reach the optimum fiber orientation via a loop of iterations that include compression molding simulation, material modeling and structural simulation.”

The alternative would have been much more time-consuming and expensive physical testing, including high-cost CT scans to evaluate the fiber orientation. “Carrying out most of the validation using Simcenter Multimech was far more cost-effective and made the project viable,” says Kapshammer.

Reverse engineering material properties

One challenge faced by Kapshammer was the material received from the supplier was the sheet molding compound (SMC) where the resin and fibers are already combined. “To build accurate simulations, we needed the individual properties of the resin and fibers,” he explains. “We had all the parameters for the fibers, but we had to find a way to reverse engineer the material properties of the resin.”

To do this, he built the macrostructure in Simcenter Multimech, and then used its capabilities to combine with HEEDS™ software to couple this model with the microstructure. “The big advantage of using HEEDS was the automated optimization,” says Kapshammer. “Without this, we’d have to do a lot more of the work manually.

“Without HEEDS this entire process would take three or more days, while with HEEDS it took less than one.”

It was the first time Kapshammer had used this coupling, but that didn’t hold him back. “I was surprised at just how easy it is to use Simcenter Multimech and HEEDS together,” he says. “The software is very intuitive, and the documentation is thorough. It’s basically plug-and-play.”

Combining Simcenter Multimech with HEEDS, which are both part of the Siemens Xcelerator business platform of software, hardware and services, was essential to validating the simulation model. As the diagram shows, before optimization with HEEDS, the model predicted a much higher opening value than after. The optimized model correlated much more closely with results from physical testing, so it was significantly more effective in accurately informing the design and the amount of material that needed to be used.

Similarly, a model analyzing the stresses on the component initially suggested the thickness of the material needed to be increased. However, after optimization and full consideration of fiber orientation, the simulation showed the stresses were within operating boundaries. So the amount of material, and thus the overall weight, could be minimized without affecting performance and durability.

Kapshammer notes the artificial intelligence (AI) capabilities of HEEDS were a significant factor in speeding up the process while ensuring accuracy. “It’s one thing to have software that runs lots of simulations with different input parameters,” he says. “But HEEDS uses intelligent randomization to improve with each cycle, so it reaches the optimal values much faster.”

Potential for structural applications

The CARBOBRAKE team at JKU have used the simulation models to identify the most promising material structures. The first prototypes will soon be tested in real-world conditions at the University of Graz Institute of Automotive Engineering (Austria), which was responsible for the overall part design. This will provide definitive validation of the flow models and structural simulations, confirming the same process is suitable for further use.

“The brake calipers are just the first stage,” says Kapshammer. “Once we show how accurate our simulations are, this could lead to many more exciting projects. It could enable the use of similar material for structural applications within vehicles, which would be a great novelty.”