Modeling Liquid Composite Molding processes with PAM-COMPOSITES, from Resin-Transfer molding (RTM) and Vacuum Assisted Resin Infusion (VARTM) to new processes using recycled materials like Resin-Transfer Pressing (RTP)
This week, I’d like to share with you some insights on advanced composites manufacturing simulation, performed by Dr Miro Duhovic and his team at the Leibniz-Institut für Verbundwerkstoffe (IVW). IVW is an international research institute based in Germany, exploring, and advancing applications and potential applications of composite materials, based on polymer matrix systems. IVW develops new designs, efficient processes, and improved composites with a customized spectrum of mechanical properties for specific industrial use, mainly in automotive, aerospace, mechanical and civil engineering.
The main fields of competencies covered include the Design of Composite Structures, Fatigue and Fatigue Life Analysis, Modelling, Simulation, and Testing of Impact Crash Behavior, Process Simulation, Tribology, Tailored and Smart Composites, Tailored Thermosets and Biomaterials, Press Technologies, Roving and Tape Processing, Impregnation and Joining Technologies and a wide range of Material Analytics. The special thing about IVW is that they handle the whole process chain from the scientific basics up to prototyping and provide the equipment to perform all needed processes both virtual and in real terms.
Frédéric: Dr Duhovic, thank you for answering my questions today. First off, can you please explain why are composite materials so challenging for the manufacturing industries?
Miro: Composites are great materials, but there are so many different possible manufacturing routes. Depending on the fiber reinforcement type as well as the many different possibilities for the resin system, a much greater number of manufacturing possibilities exist than with say — metals. Compared to metals, the materials themselves are inhomogeneous and can be highly anisotropic. This presents a significant challenge in understanding and predicting the highly nonlinear behavior of composite materials, specifically for industrial use, to safeguard the integrity of components, and to master manufacturing processes to produce parts within tolerances that meet requirements, at lower cost and with minimal scrap rates.
Frédéric: What investigation methods do you use to better understand composite manufacturing processes?
Miro: At the IVW, we combine a large research park (7 200m2) of composites specific material characterization and testing equipment together with simulation tools, including PAM-COMPOSITES, to help us carry out research oriented around composites design. This includes the design of the final part properties as well as the manufacturing process needed to get there. We have a wide variety of material characterization equipment for investigating the physical, chemical, and structural properties of composite material at the various stages of their creation.
Frédéric: What manufacturing processes do you simulate using ESI’s composites manufacturing simulation software, PAM-COMPOSITES?
Miro: Although we try to simulate all the composites manufacturing processes, which we research at the IVW, a large part of our research focus is on the simulation of Liquid Composite Molding (LCM) processes. This covers processes like Resin-Transfer molding (RTM), Vacuum Assisted Resin Infusion (VARTM) and a lot of variations of the two (e.g.: C-RTM, Wet Pressing, etc.)
Sometimes we even consider and develop new processes, such as Resin-Transfer Pressing (RTP) or Resin Transfer Infusion (RTI), in which we aim to use recycled materials. For these new processes, ESI’s Visual-RTM provides us with the capability to simulate these processes and to look deeply into some of the important parameters which can help us optimize the manufacturing and to achieve the best part quality. Beyond composite manufacturing process simulation, we also use PAM-COMPOSITES for very advanced research on material characterization, as you will see in the video below.
Frédéric: Can you give us an example of a research project where simulation was instrumental in achieving your goals?
Miro: One of our current research topics in the areas of LCM is the detailed investigation of through-thickness permeability behavior and the hydrodynamic compaction effects that occur. Hydrodynamic compaction is an important aspect of material characterization, as the idea is to measure the through-thickness permeability at a specific target fiber volume fraction. However, what if the through thickness impregnation process actually changes during infusion? And do we know by how much for various textiles, and process parameters? The answer is no, which is why it’s very important to investigate this!
As part of a recent work funded by the Deutsche Forschungsgemeinschaft (DFG) (DFG reference Mi 647/31-1), we have investigated hydrodynamic compaction effects by creating a highly detailed model of our measurement device, the “HykoPerm”. The real device is equipped with many sensors (pressure, flow rate, ultrasonic) all of which can be used to validate our model. The model itself is built-up using Visual-RTM and uses the advanced fluid-structure-interaction capabilities of the software’s (C-RTM/3D VARTM) functionality. The result is detailed information on the fiber volume fraction distribution in the preform specimen being impregnated.
Frédéric: Could you compare these results with experimental measurements?
Miro: Yes, absolutely. We were very happy to see a very good correlation between real tests and simulations. As you will see on the graph below, for all measurements we took, the results were exactly the same or at least within our measured results bracket. We are looking forward to publishing our complete research very soon, which we will share with you for download.
In conclusion, PAM-COMPOSITES is a reliable and valuable simulation tool, not only for industry but also for research, giving the opportunity to consider the most complex problems, which are usually ignored by industry. The Leibniz-Institute für Verbundwerkstoffe and ESI Group have enjoyed a fruitful relationship for more than 10 years and with the growing importance of composites will continue to do so in the future…
Dr. Miro Duhovic has accumulated 20 years working in the field of composite materials manufacturing and process simulation. Has consulted for many of the largest Automotive, Aerospace, and Plastics/Composites manufacturers in Europe and in the US. He is currently the head of the Process Simulation group at the Leibniz-Institut für Verbundwerkstoffe GmbH (Institute for Composite Materials) in Kaiserslautern, Germany, and is both a Lecturer at the Technical University of Kaiserslautern as well as an Honorary Research Fellow at the University of Auckland, New Zealand.