Numerical and experimental development of laminates made of auxetic materials using strand deposition process for highly dynamic applications.

• Applicants: Professor Dr.-Ing. Christian Bonten; Professor Dr.-Ing. Stefan Weihe
• Subject Area: Polymeric and Biogenic Materials and Derived Composites ; Plastics Engineering
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 407085865

Auxetic structures offer completely new development possibilities for products. In the previous project, it was possible to gain initial insights into a mechanical behavior that had previously been little considered. Here, the auxetic structures were subjected to quasi-static loading. One of the insights gained from these investigations is that possible fields of application for these structures could be in the area of safety-relevant components, which are intended to provide protection against the penetration of foreign bodies under highly dynamic loads, such as in a crash. Current publications deal purely simulatively with the impact behavior of an impactor on auxetic structures. Due to the fact that the impact behavior is highly dynamic and outside of a reversible deformation process, this project will be the first to test the generalized hypothesis of resistance to penetration of auxetic structures. The auxetic lattice structures are also characterized by a lightweight construction which, when struck by a foreign body, abruptly compresses locally to a high degree, thus preventing penetration. Due to this loading method, it is sufficient to consider the auxetic structure as a two-dimensional laminate with different numbers of layers. The previously used auxetic structure of the inverse honeycomb will continue to be used. Now, in order to achieve maximum energy absorption upon impactor impact in addition to protection against penetration, which exposes the structure to be protected to as little mechanical stress as possible, the concept within the scope of the project applied for is to combine the inverse honeycomb structure with the related "real" honeycomb structure as a laminate. The additive manufacturing process used so far, the strand deposition process, is also to be used in this follow-up project so that the laminate, consisting of layers with both honeycomb structure and inverse honeycomb structure, can be produced in one process step. The research project projected here aims to use the fused filament fabrication (FFF) process with the plastics polyactide (PLA) and polybutylene adipate terephthalate (PBAT) to produce laminates that have a high resistance to impactor penetration and a high level of energy absorption. However, the main focus will be on predicting the response of the two-dimensional laminate structure with different proportions of inverse honeycomb structure and "real" honeycomb structure using simulation. For the prediction of the optimal structure-property relationship, a machine learning algorithm is also to be used, which must first be trained within the scope of the project applied for.

• DFG Programme: Research Grants