Periodic Reporting for period 2 - BEDYN (Development of a methodology (test, measurement, analysis) to characterize the BEhaviour of composite structures under DYNamic loading)
Reporting period: 2022-01-01 to 2023-06-30
During their service life, aerospace structures can be subjected to a variety of dynamic loading cases. Crash/impact is one of the most concerning cases due to its possible disastrous consequences. Impacts on aerospace structures can be produced by the accidental or deliberate hit of an object into aircraft. Hailstones, bird strikes, runaway debris, tyre fragments or even other fragments from the aircraft structure that could be ejected in case of an 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 from 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.
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. Different main objectives can be defined:
Ob. 1) Define a modelling approach for dynamic loading events, suited to industrial needs for emergency situations applications.
Ob. 2) Define dynamic tests, which include the definition of: specimens, test setups, and data reduction methods. Three different specimen levels are set: “coupon”, for characterizing basic properties of the composite material (ply), interlaminar (delamination) and adhesive interfaces; “element”, they include what can be understood as small size demonstrator (under this category the response of the flexural, notch effects and bearing will be analysed); “structure”, they are devoted for characterizing the behaviour at a subcomponent level under out-of-plane dynamic loads. In order to describe properly the possible dynamic effect in some material/structure behaviours, a quasi-static test campaign is also considered for any of the specimen levels accounted for.
Ob. 3) Define a calibration and validation process of the models.
Ob. 4) Demonstrate and evaluate the proposed methodology based on tests performed.
As the BEDYN project has achieved the defined objectives, it can be concluded that BEDYN has contributed to the consolidation of the use of numerical simulation in the design phase of polymer-based composite structures under dynamic loading. The BEDYN project has addressed innovative technologies that allow better product development thanks to a better knowledge of the behaviour of composite materials under dynamic loading. The maturing and validation of technologies is a key aspect of integrating research into the development process of industrial activities and next generation aircraft.
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 from 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.
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. Different main objectives can be defined:
Ob. 1) Define a modelling approach for dynamic loading events, suited to industrial needs for emergency situations applications.
Ob. 2) Define dynamic tests, which include the definition of: specimens, test setups, and data reduction methods. Three different specimen levels are set: “coupon”, for characterizing basic properties of the composite material (ply), interlaminar (delamination) and adhesive interfaces; “element”, they include what can be understood as small size demonstrator (under this category the response of the flexural, notch effects and bearing will be analysed); “structure”, they are devoted for characterizing the behaviour at a subcomponent level under out-of-plane dynamic loads. In order to describe properly the possible dynamic effect in some material/structure behaviours, a quasi-static test campaign is also considered for any of the specimen levels accounted for.
Ob. 3) Define a calibration and validation process of the models.
Ob. 4) Demonstrate and evaluate the proposed methodology based on tests performed.
As the BEDYN project has achieved the defined objectives, it can be concluded that BEDYN has contributed to the consolidation of the use of numerical simulation in the design phase of polymer-based composite structures under dynamic loading. The BEDYN project has addressed innovative technologies that allow better product development thanks to a better knowledge of the behaviour of composite materials under dynamic loading. The maturing and validation of technologies is a key aspect of integrating research into the development process of industrial activities and next generation aircraft.
The BEDYN project can be divided into two work technical sets: experimental and numerical. For each set, different activities were carried out until the end of the project (M1-M36: final period).
For experimental activities, the main work was related to the definition of the tests to be performed, in agreement with the industrial topic manager. This includes the definition of specimens, test setups and appropriate data reduction methods for both quasi-static and dynamic loading conditions. In some cases, the definition was based on work published in the literature and adapted to the consortium facilities using numerical simulations. Other tests required further research and new test methods were developed. In addition, other experimental activities were carried out: fabrication of specimens, design and fabrication of test rigs, and execution of tests under quasi-static and dynamic conditions, including data reductions, reporting and analysis. More than 600 tests have been carried out in the BEDYN project. In terms of numerical activities, the main activity has been the formulation and implementation of two constitutive models that take into account the effect of strain rate on the associated material properties (including stiffness, strength and fracture toughness). These models allow the simulation of delamination as well as intralaminar failure of thermoset based composites.
Finally, the overview of the results is: four linked doctoral theses; one open access peer-reviewed paper and ten other papers under development to be published after BEDYN; 13 participations in national and international conferences and at least three more participations will be done after BEDYN; creation of new networks with new partners to continue working on the topics developed in BEDYN.
For experimental activities, the main work was related to the definition of the tests to be performed, in agreement with the industrial topic manager. This includes the definition of specimens, test setups and appropriate data reduction methods for both quasi-static and dynamic loading conditions. In some cases, the definition was based on work published in the literature and adapted to the consortium facilities using numerical simulations. Other tests required further research and new test methods were developed. In addition, other experimental activities were carried out: fabrication of specimens, design and fabrication of test rigs, and execution of tests under quasi-static and dynamic conditions, including data reductions, reporting and analysis. More than 600 tests have been carried out in the BEDYN project. In terms of numerical activities, the main activity has been the formulation and implementation of two constitutive models that take into account the effect of strain rate on the associated material properties (including stiffness, strength and fracture toughness). These models allow the simulation of delamination as well as intralaminar failure of thermoset based composites.
Finally, the overview of the results is: four linked doctoral theses; one open access peer-reviewed paper and ten other papers under development to be published after BEDYN; 13 participations in national and international conferences and at least three more participations will be done after BEDYN; creation of new networks with new partners to continue working on the topics developed in BEDYN.
The direct impact of the BEDYN project is the generation of scientific and technological knowledge for the characterisation of thermoset-based composites reinforced with long and oriented carbon fibres at medium/high loading rates. This is a global methodology that combines an experimental and a numerical approach for a better assessment of the material behaviour under the prescribed loading conditions. The main results derived from the BEDYN project are the definition of a methodology for the definition of experimental tests under dynamic loads, as well as the development of advanced constitutive models that describe the behaviour of the material adequately for the simulation of structures that may be immersed in loading conditions of this type. For the definition of most of the tests, it has been a particular research challenge, with many difficulties to be solved covering specimen definition, test set-up and adequate data reduction.
This is why the project has four related doctoral theses, two of which have been fully dedicated to the project, as well as one post-doctoral researcher and three senior researchers. Due to the research activity, a total of 13 participations in national and international conferences have been carried out so far, where the work carried out at BEDYN has been presented, and which in many cases has aroused the interest of researchers involved in similar topics. In these participations, networks have been established to collaborate on topics that give continuity to the BEDYN project.
A total of 11 papers are expected to be published in peer-reviewed open-access publications, of which one has already been published in May 2023. As the results of the BEDYN project are public, they will have a relevant scientific impact that will be freely available.
Expected impacts of the Project to be highlighted:
- Contributing to the resilience of transport industries, such as aeronautical and automotive, by improved structures of polymer-based composites is evident. Better designs using polymer-based composites imply lower material consumption and weight reduction.
- Encouraging innovation in the design of composite structures with the BEDYN methodology to develop more European competitive products.
This is why the project has four related doctoral theses, two of which have been fully dedicated to the project, as well as one post-doctoral researcher and three senior researchers. Due to the research activity, a total of 13 participations in national and international conferences have been carried out so far, where the work carried out at BEDYN has been presented, and which in many cases has aroused the interest of researchers involved in similar topics. In these participations, networks have been established to collaborate on topics that give continuity to the BEDYN project.
A total of 11 papers are expected to be published in peer-reviewed open-access publications, of which one has already been published in May 2023. As the results of the BEDYN project are public, they will have a relevant scientific impact that will be freely available.
Expected impacts of the Project to be highlighted:
- Contributing to the resilience of transport industries, such as aeronautical and automotive, by improved structures of polymer-based composites is evident. Better designs using polymer-based composites imply lower material consumption and weight reduction.
- Encouraging innovation in the design of composite structures with the BEDYN methodology to develop more European competitive products.