Investigation of a metamodel-based methodology to optimise the component properties of discontinuous long fibre reinforced plastics by systematic design of manufacturing processes

• Applicant: Professor Dr.-Ing. Christian Hopmann
• Subject Area: Plastics Engineering
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 460280822

Discontinuous long fibre reinforced plastics (DLP) currently represent one of the most important material classes in the field of fibre composites. For the processing of these materials, primary forming processes are generally used to produce near-net-shape components. During processing, flowing of the DLP occurs. This influences the fibre orientations, determining the mechanical properties of the part. The mechanical properties resulting from a specific process configuration can be predicted by simulation. However, since these are computationally expensive and time-consuming, not all possible configurations can be simulated, which limits reaching a desired mechanical property profile.The aim of the project is a methodology for the optimisation of DLP processing processes using the example of the initial occupancy state in the compression moulding of thermoset and thermoplastic DLP. Due to the high complexity of this process and the long chains of action, the metamodeling approach of the shaping influences on the final part properties is pursued. By metamodeling, relationships can be replicated that were determined by drawing samples of a complex model or context. In order to optimise the process with regard to the optimisation goals used in the project (minimisation of part deformation under torsion and three-point bending), the metamodels are evaluated iteratively with the aid of a genetic algorithm and extended by additional process configurations and resulting deformations. The convergence behaviour of the optimisation approach is investigated with respect to its dependence on the degree of metamodel abstraction, part geometry, load case and temperature induced material effects.The modelling is therefore carried out on two different abstraction levels. On the first abstraction level, the direct relationship between input parameters and the resulting component deflection is modelled. This approach, also called "black box", neglects the behaviour of the DLP during processing as well as the complex relationships between flow and mechanical component properties. On the second abstraction level, two metamodels are coupled. Firstly, a metamodel of the discontinuous flow of the DLP during the process and thus of the material behaviour itself is created. Secondly, a black box approach used for modelling of the resulting component behaviour. Therefore, an isolated analysis of the influence of near-process metamodeling is possible. Validation of the metamodels will be performed by cross-validation. Additionally, an evaluation of the generalizability of the optimisation approach will be carried out.

• DFG Programme: Research Grants