Development of a methodology (test, measurement, analysis) to characterize the BEhaviour of composite structures under DYNamic loading

Advanced polymer-based composite materials are included in the set of materials that improve and advance the aviation industry. In this field, it is well known that the main issues of concern are the greenhouse gas emissions and the fuel costs, which are the largest operating expenses for airlines. Therefore, the development of technologies to address these issues has clear economic and environmental benefits.

When composites are to be used in structural components, a design development program is generally initiated during which the performance of the structure is assessed prior to its use. Typically, the process of design starts with the analysis of a large set of simple small specimens and, when sufficient knowledge is acquired at this level, it is changed over to a more complex structure but carrying out fewer tests. This methodology is quite mature and well stablished for static and fatigue loads. 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. In the literature, the effect of not having a standard methodology can be found even at basic material characterization, where often there is no agreement on the trend of the behaviour of the analysed property with regard to the loading rate (or strain rate).

During its service life, aerospace structures can be subjected to a variety of dynamic loading cases. Crash/impact is one of the most concerning case due to its possible disastrous consequences. Impacts on aerospace structures can be produced by the accidental or the deliberate hit of an object into aircraft. Hail stones, bird strikes, runaway debris, tyre fragments or even other fragments from the aircraft structure that could be ejected in case of accident (i.e. uncontained rotor engine failure) are the main examples produced in the aerospace sector. Therefore, it is crucial to understand how the materials used in the aerospace sector behaves under dynamic loadings.

Composite materials may exhibit strain rate effects, therefore robust and industrial dedicated dynamic coupon and element level tests, analysis and modelling methods are then necessary to design and certify composite airframe structures. The analysis tools based on static formulations could be far away of the actual material and structural response, and hence a dedicated methodology is needed for dynamic loading states. This is what the proposed BEDYN project will deal with. Accordingly, the aim of BEDYN project is to address a methodology (including innovative tests, measurements, and analysis methods) to properly characterize the dynamic behaviour up to rupture of composite structures submitted to a dynamic loading. Different issues will be dealt in BEDYN project:

  • Define a modelling approach suited to industrial needs for emergency situations applications (e.g. bird strike on a composite structure).

  • Define associated dynamic tests (samples, experimental setup, etc.).

  • Define a calibration and validation process.

  • Demonstrate and evaluate the proposed methodology based on tests performed within the BEDYN activities.