More than fibers in sight: Fraunhofer LBF develops application-oriented methods for the simulation of plastic components
Numerous factors influence the material and component behavior of plastics. This has an impact on practical component design: Not only the fiber orientation plays an important role, but also the material behavior material behavior that results from contact with media or from superimposed load cases. So far, there are no established methods for this. In addition, it is not immediately obvious which aspects must be taken into account in order to design components correctly. These challenges are addressed by the Fraunhofer Institute for Structural Durability and together with industry consultants by developing customer-specific methods. customer-specific methods. The aim is to use existing structures and available available tools and to integrate the methods in the best possible way into structures. The Darmstadt institute accompanies its partners from simulation and material modeling to mechanical testing and evaluation of the evaluation of the results. The results are simulation-based methods which take into account highly individual load scenarios and thus enable resource-efficient, lightweight and innovative component design.
Plastics exhibit a very complex material behavior that depends on various influencing parameters. This can be seen, for example, in the use of reinforcing fibers in technical components. Although they significantly improve the mechanical behavior, they also lead to complex direction-dependent material and component behavior. In addition, environmental influences such as temperature and humidity, but also contact with different media (gasoline, diesel, AdBlue) significantly affect material and component behavior. These loads often overlap when, for example, media come under high temperature and pressure, which further complicates the component design.
Exposure: It's not just forces and pressures that count
During the design phase of technical components, the first step focuses on the acting mechanical loads. For an isotropic material behavior, these can be defined and considered directly in simulation applications. If the material is fiber-reinforced, the fiber orientation from a coupled injection molding simulation or via phenomenological approaches must be integrated into the mechanical simulation to take anisotropic material behavior into account. Corresponding tools usually also allow the transfer of results from a shrinkage and warpage simulation in order to take into account the deformed structure and any stresses that may already have arisen as a result.
Media contacts that change the mechanical behavior, for example through swelling or material degradation, cannot be directly defined as a boundary condition in a mechanical simulation. Therefore, the changed material behavior cannot be directly represented in the structural simulation. For this reason, so-called reduction factors are often used, which are frequently taken from literature sources of comparable materials in the application. For example, a permissible stress or strain is adjusted and the component is designed accordingly. This can be a quick approach for a preliminary design, for example to estimate the basic suitability of a material. However, for a load-appropriate and resource-efficient component design, such significant influencing variables must also be investigated experimentally and the effects correctly recorded in the simulation using practicable methods.
Customized simulation strategies for rapid product development
Together with industrial partners, Fraunhofer LBF develops customer-specific, application-oriented methods and accompanies their transfer into existing processes and existing infrastructure. The development of such methods always adapts to the respective design stage. While a simplified strategy can be used for initial evaluations at the preliminary design stage, more detailed simulations can be considered later, when more information on the component and material is available, in order to design the component in a load-compliant and resource-efficient manner. The result: fewer cost-intensive development loops, for example for components in the automotive or aerospace industries.