Multi Hardener Laminates (MHL) – Development of a material concept for reducing temperature gradients in thick-walled components

• Applicant: Professor Dr.-Ing. Dieter Meiners
• Subject Area: Plastics Engineering
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 530560189

In the manufacture of thick-walled fiber composite parts, heat is generated during the exothermic curing reaction of the duromer resin system. If this is not taken into account during the manufacturing process, large temperature differences occur within the component, which only dissipate slowly due to the low thermal conductivity of the polymer material. As component thickness increases, the generated heat accumulates in the middle layers of the component. Higher temperatures accelerate the curing reaction, which in turn leads to faster heat release. The resulting temperature differences lead to different curing speeds within the component and facilitate the formation of residual stresses. Residual stresses can lead to distortion and deterioration of the mechanical properties in the finished component, and in the worst case, material degradation can occur due to overheating. The goal of the proposed project is to reduce the generated heat by using hardener systems of dissimilar reactivity. The material concept to be researched envisages reducing the heat generated in the inner layers of the component by using less reactive hardener components. At the same time, sufficient heat is generated in the outer layers by using a more reactive resin system to cure the inner layers. To achieve this goal, suitable resin-hardener systems are first selected and characterized. Subsequently, a simulation model is created that represents the curing of different resin-hardener systems within a component and the resulting temperature distribution. An optimization algorithm is then used to derive a layer-by-layer infusion plan from the model for 15 mm, 30 mm and 60 mm thick test components. The test components are manufactured using the online prepreg system and hot press available at PuK. During the manufacture of the components the temperature distribution in the component is monitored and used to validate the simulation model. The manufactured components are subjected to mechanical tests to investigate the effect of using different resin-hardener systems within a component.

• DFG Programme: Research Grants