Impact damage resistance enhancement of natural fiber composite laminates (IDEFICS)

• Applicant: Professor Dr.-Ing. Sebastian Heimbs
• Subject Area: Polymeric and Biogenic Materials and Derived Composites ; Lightweight Construction, Textile Technology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 520748743

In the context of sustainability, the interest in bio-based natural fiber composite materials for engineering applications in the field of aeronautics or wind energy is high. However, natural fiber composites are known to exhibit poor resistance against foreign object impact loads compared to conventional glass or carbon fiber composites with significant damage developing already under low impact energies. On top, they are prone to moisture uptake and consequential property reduction, limiting their general utilization. This project proposal aims at researching a novel solution for both these drawbacks, making use of the crack-stopping and moisture-blocking properties of ductile or hyperelastic interlayers inside the laminate, as successfully demonstrated in fiber-metal laminates like GLARE. However, the objective of this proposal is to select fully bio-based and bio-degradable materials only, for fibers (e.g. flax), matrix (e.g. polylactic acid) and interlayers (e.g. bio-based rubber plies), yielding a fully eco-friendly structural material. In the course of the project, we aim to select appropriate material constituents, manufacture specimen plates with different lay-ups and experimentally introduce impact damage with variable energies on an impact drop tower. Finally, the residual strength after impact under compressive and tensile loads is tested for each material system to quantify and compare their damage resistance and residual strength capabilities. The performance of the novel configurations with crack-stopping interlayer is supposed to be assessed under dry and hot/wet conditions and is compared with a regular natural fiber composite laminate and with a glass fiber composite material as reference. In parallel to the experimental test campaign, numerical simulation models of the natural fiber composite with crack-stopping interlayers are supposed to be developed and validated with the available test data, making use of adequate intralaminar and interlaminar fracture laws. The purpose of the simulations is to obtain a fundamental understanding of the damage process and progression under impact loads and to study and identify efficiently further promising lay-up variants beyond the limited test matrix. This project will add valuable new insights to the existing body of knowledge of methods for improving the impact damage resistance of natural fiber composites thanks to the experimental and numerical research studies and aims at providing novel material concepts that are competitive to conventional composite materials.

• DFG Programme: Research Grants