Abstract

The methodology of design of polymer-based composite structures under static loadings, and even fatigue loads, is quite mature and well stablished. However, for intermediate and high dynamic loading conditions, the methods are still under development and often limited to academic research levels, without any type of standardization. It is crucial to understand how the materials used in the aerospace sector behave under dynamic loadings. Composite materials may exhibit strain rate effects and the analysis tools based on static formulations could be far away from the actual material and structural response, therefore robust and industrial dedicated dynamic tests, analysis and modelling methods are then necessary to design and certify composite airframe structures. This is what the proposed project will deal with. The aim of BEDYN project is to address a methodology to properly characterize the dynamic behaviour up to rupture of thermoset polymer-based composite structures submitted to dynamic loading. BEDYN is a European granted Clean Sky 2 Joint Undertaking (JU). 

Abstract

The behaviour of composite materials under dynamic loading conditions has been a subject of research for the last two decades. When subjected to dynamic conditions, composite materials show a significant sensitivity to strain rate. This is critical for a correct simulation of the behaviour of composite structures under impact. Currently, a few studies have been carried out on the analysis of strain rate sensitivity of the fracture toughness. These studies have reported different conclusions for the same material (IM7/8552), indicating that the optimal technique for characterising this property under high strain rate loading remains unresolved. In this work, it has been carried out dynamic characterization test on the fracture toughness using the Split Hopkinson Pressure Bar. It has been developed a new methodology for obtaining an accurate synchronization between Hopkinson bar data and high speed camera. Using the proposed methodology a good repeatability has been obtained for dynamic tests.