Fraunhofer Institute for Industrial Mathematics ITWMAt the Fraunhofer ITWM, we develop simulation methods that help to better understand and optimize production processes. One current example is our new solution for the simulation of sheet molding compounds (SMC), which we use to precisely model the production of fiber-reinforced plastics. SMC is a versatile material made of glass or carbon fibers and resin that is frequently used in the automotive industry, but also in many other industries. The core of our approach is the realistic prediction of the orientation of fiber bundles in the material, a decisive factor for the strength and quality of the finished component.
Leichtbau Produktion Automobil: Montage von Autos
The simulation of processes relating to sheet moulding compounds (SMC) enables the virtual design and optimization of fibre-reinforced plastic components – a key component for lightweight, stable and economical lightweight construction, for example in the automotive industry.
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Rethinking SMC Process Simulation: Model Fiber Orientation Realistically – Increase Component Quality in a Targeted Manner
Efficient Materials in Lightweight Construction: Innovative Simulation of Fiber Orientation in Sheet Molding Compounds
SMC have been among the most established fiber composite materials for decades and are well suited for lightweight construction. The orientation of the fibers largely determines how stable and resilient the finished component is. Long fibers in a thermosetting resin make the material stable, lightweight and suitable for series production. Carbon fiber-reinforced variants (C-SMC), which can be processed with fiber content of up to 60 percent, are currently gaining in importance. In the automotive industry in particular, SMCs help to make vehicle structures lighter – which reduces both energy consumption and environmental impact.
Realistic SMC Simulation: Understanding Flow Behavior, Using Material Efficiently
Pressing SMC is a complex process in which temperature, pressure and material behavior must interact precisely. The fibers form a network that determines the strength, flow behavior and material quality. If the fiber orientation is not taken into account during the development process, this can lead to weaknesses in the component later on.
Because fibers and resin move at different speeds during the pressing process, it is not easy to reproduce this process realistically. This is where our tool, which is based on our FLUID software solution, comes in: Resin and fibers can flow at different speeds, which can create regions where there is significantly less fiber material. The permeabilities can be determined using microscale simulations with GeoDict.
We check and validate the predictions using computer tomography (CT) image analysis – even for complex component geometries such as a dashboard from automotive production.
From Microscale to Component Performance – Precise Simulation Data Improves SMC
Our method provides accurate input data for the structural analysis of SMC components. This makes it possible to use the material more efficiently and at the same time increase the quality and safety of the products.
SMC Simulation of a Lightweight Component (Car Dashboard)
Our researchers developed a two-phase model that takes into account the different flow rates of resin and fiber bundles for the first time in an industrial context. This is particularly relevant for long fibers with a high volume fraction.
- The method simulates the 3D flow of resin and fibers.
- The permeability of the fiber bundles – i.e. how well the resin can flow through the fibers – is estimated using microscale simulations.
- Measuring the viscosity of the resin is sufficient for the simulation. Measurements for the entire mixture are not necessary.
Validation: How Well Does the Simulation Match Reality?
The results of the simulation were compared with high-resolution CT scans of the material. This showed that:
- The predicted fiber orientations agree well with the image data.
- The predicted flow front during mold filling of complex geometries also matches the experimental observations.
Fiber Orientation in View: Polarization Imaging Complements the Simulation
In addition to model-based prediction, we also rely on innovative imaging methods to make the orientation of fiber bundles visible – directly on the material surface. Carbon fibers reflect light in a characteristic way: They polarize it. The polarization camera developed by the Fraunhofer Institute for Integrated Circuits IIS uses precisely this effect to show the fibre orientation in carbon fibre-reinforced sheet molding compounds (C-SMC). This is done in real time, without contact and without time-consuming sample preparation. The method is suitable both for quality control in ongoing production and for validating simulation data. The method therefore offers a valuable addition to simulation and CT analysis, especially for surface characterization and process optimization.
Outlook: Structural Simulation of SMC Components for Efficient Materials
A realistic simulation of the SMC process is possible if resin and fiber behavior are considered separately – and the results are checked with high-resolution image data. The method improves the predictability of component properties and helps to use materials more efficiently.
»For the first time, our solution provides robust and industrially practicable input data for the structural simulation of SMC components,« explains project manager Dr. Hannes Grimm-Strele from Fraunhofer ITWM. »This enables an end-to-end digital process chain – from the material model to the virtual component test.«
The new method is a further step towards more efficient materials, optimized production processes and lighter, more efficient components, especially in lightweight automotive construction.