Influence of temperature on the behaviour at fibre misalignment in thick-walled Fibre Reinforced Composites

• Applicant: Professor Dr.-Ing. Bodo Fiedler
• Subject Area: Plastics Engineering ; Lightweight Construction, Textile Technology
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428324840

Fibre reinforced polymers (FRP) are established as a design material for structural parts in various applications. However, manufacturing induced composite imperfections, in-plane as well as out-of-plane, is critical, because the fibres are no longer orientated in loading direction due to the misalignment, which reduces strength and stiffness of the laminate significantly. The aim of this research project is the investigation of the influence of structural discontinuities in the shape of local fibre misalignment (in-plane) and on laminate level layer waviness (out-of-plane) on the mechanical properties of FRP. A special focus is set on the influence of the ambient temperature on the behaviour of so called thick laminates under uniaxial compression and multiaxial loading conditions.When investigating a size effect of the mechanical properties of FRP, it is often not clear whether it is an actual size effect of the material or whether other influencing factors, such as a reduction in manufacturing quality with increasing thickness, play a role. In this case, defects that have been artificially introduced can provide further insights into the influence of production deviations in the scaling of FRP laminates, while ensuring a consistent production quality.The compressive behaviour of FRP is significantly influenced by the matrix properties, which are temperature-dependent. The basis of the investigations is therefore the characterization of the matrix with regard to the thermal and mechanical properties as well as the temperature-viscosity behaviour. The temperature-viscosity behaviour is decisive for the development of the HD-RTM process.The applicability of mechanical parameters and material properties determined in experiments with thin specimens to thick-walled structures has not been clarified and will be investigated within the framework of the project.Finally, the findings will be used for the multiaxial testing of test structures. Thus, the influence of fibre misalignments and displacements at different temperatures on component-like structures can be investigated and correlations for critical defects can be derived.

• DFG Programme: Research Grants