Advanced material card creation for SMC molding simulation

»SIMUTENCE engineering and simulation methods enable the simulation of SMC molding processes. But how does characterization and material card creation work? We’ll answer this question below.«


The main advantages of discontinuous fiber-reinforced polymers are low manufacturing costs, as well as the design freedom for complex geometries. Sheet Molding Compound (SMC) has become a highly sought-after material, not only for exterior parts in the automotive industry but even more so for structural applications through carbon fiber reinforced SMC. Its uses even extent to the aerospace industry for manufacturing complex shapes with high thermomechanical requirements.


For efficient product and process design within a digital product development cycle, the simulation of the manufacturing process through molding simulation is crucial. However, there is neither a widely accepted modeling approach nor a standardized characterization technique for material card creation.


SIMUTENCE is a spin-off company from the Karlsruhe Institute of Technology (KIT) in Germany with a strong background in SMC molding simulation through the International Research Training Group (IRTG) “Integrated engineering of continuous-discontinuous long fiber reinforced polymer structures”. One major result of the first phase of the IRTG in the context of SMC molding simulation was the thorough experimental investigation and modeling of SMC flow and the development of a suitable characterization approach for the creation of material cards for SMC molding simulation.


Together with Blackwave, located in Munich, Germany, an expert for the design and manufacturing of carbon fiber reinforced SMC (CSMC) components, we adopted our approach for SMC material card creation and molding simulation within a validation study. Two different CSMC materials from Astar and Polynt were characterized, material cards were created and molding simulation was validated for an aircraft rim. In the following, we present the SIMUTENCE approach for material card creation and related results from our joint validation project.


The highly specific characteristic for SMC materials is the so-called plug flow during molding, which originates from a thin lubrication layer at the tool-charge interfaces. Here, it is important to know, that this characteristic differs completely from long fiber-reinforced thermoplastics (LFT), which shows a so-called fountain flow. Thus, modeling techniques developed for LFT molding can’t be directly applied to SMC molding, due to the differing flow mechanisms induced by the tool-charge interaction.


Apart from that, SMC materials are highly filled fiber suspensions, which induce an anisotropic viscosity concerning shear and elongational deformation. Therefore, the modeling of an anisotropic viscosity in molding simulation, accompanied with the characterization of the shear and elongational viscosity, as well as the lubrication layer, are essential for accurate SMC molding simulations.

Simple shear loading of a unit cell

Elongational loading of a unit cell


To consider the above-outlined SMC characteristics in the creation of material cards, our approach uses a manufacturing process-oriented material characterization. A plate molding tool, owned by Fraunhofer ICT and equipped with several pressure sensors, is used to characterize the elongational viscosity and the lubrication layer in a so-called press viscosity test. This way, not only the press force but also the local pressures are measured. Based on this, the contribution of the material force and the lubrication layer to the local pressures can be separated.

Plate molding tool equipped with pressure sensors

For material card creation the data is subsequently processed using a proprietary Python code to parametrize an anisotropic viscosity model following the Dinh-Armstrong approach, as well as a hydrodynamic friction model following a power-law approach. Fiber reorientation due to material flow is predicted by Folgar-Tucker’s approach and considered in the evaluation of the anisotropic viscosity. Based on this, the SMC material card for SimuFill, the SIMUTENCE product for compression molding simulation, is obtained.


In our validation project with Blackwave, we applied the above-outlined procedure to create material cards for one CSMC material from Astar and Polynt, respectively. An initial mold coverage of 30% and two different deformation rates were considered for the press viscosity tests. For material card creation, the signals from the local pressure sensors are compared to the predicted pressures and the parameters of the elongational viscosity and the lubrication layer model are tweaked automatically using an optimization procedure until a good agreement between measured and predicted pressure signals is obtained.

An exemplary fitting result for the press viscosity test at a high deformation rate

An exemplary fitting result for the press viscosity test at a low deformation rate

These exemplary results show, apart from some minor deviations at the onset of material flow, that our approach for SMC flow modeling captures the rheological (elongational viscosity) and the lubrication stress over a wide range of flow lengths as well as different deformation rates.


SMC materials reveal show unique flow characteristics during molding, which originates from the so-called plug flow and the anisotropic viscosity. Therefore, existing techniques for LFT molding simulation and characterization are not directly applicable to SMC materials. SIMUTENCE is using an approach for material modeling and material characterization originally developed at KIT to take into account these specific material characteristics. Based on this, reasonable results for the prediction of mold filling and required press forces are obtained, which will be demonstrated for the Blackwave aircraft rim.

Any Questions?

Do not hesitate to get in contact with us if you have any questions or if you are interested in a collaboration. We are looking forward to receiving your request!


  • Görthofer et al. (2019): Virtual process chain of sheet molding compound: Development, validation and perspectives. In: Composites Part B: Engineering 169, S. 133–147. DOI: 10.1016/j.compositesb.2019.04.001.
  • Hohberg (2019): Experimental investigation and process simulation of the compression molding process of Sheet Molding Compound (SMC) with local reinforcements. Doctoral studies. Karlsruhe Institute of Technology, Karlsruhe. Institute of Vehicle System Technology.