ERC Advanced Grant NABUCCO - New Adaptive and BUCkling-driven COmposite aerospace structures   

@ POLIMI

NABUCCO develops radically new concepts of adaptive and buckling-driven composite structures for next generation aircraft. In aeronautics, buckling is generally avoided because it causes stiffness reduction, large deformations and can result in a catastrophic collapse. Instead, NABUCCO considers buckling no longer as a phenomenon to be avoided, but as a design opportunity to be explored for its groundbreaking potentialities. The idea is to use buckling drawbacks in a positive way, to conceive, design and realize adaptive composite structures and aircraft morphing wings.

A strongly coupled computational-experimental framework is developed based on novel analytical formulations, neural networks algorithms for large multi-objective optimizations, high-fidelity simulation methodologies and advanced test techniques.

The structures developed in the NABUCCO project will be able to adapt their shape during different flight conditions, acting on two of the biggest levers for the future of clean aviation: reduced weight and increased efficiency. 

Funded by European Research Council (ERC)

A Comprehensive Investigation of Sustainable Welded Thermoplastic Post-Buckled Composite Structures   

@ POLIMI

In the recent years, the aeronautical sector has shown an increase interest in research and development of thermoplastic composite materials. Indeed, the use of thermoplastic composites can improve the sustainability of the aeronautical sector, and decrease the manufacturing time and costs. Besides, they offer the possibility of welding stringers to the skin, providing a viable path forward for unitized composite structures. However, there is not much experimental understanding of the mechanisms involving welded joint failure, and the computational tools available for the simulation of thermoset composites have not yet been completely assessed for thermoplastic materials.

The main objectives of the proposed research are to experimentally investigate welded thermoplastic composite structures, and to develop an experimentally-validated numerical approach to enhance the modelling of post-buckling behavior of welded thermoplastic composite stiffened panels. 

Funded by European Office of Aerospace Research and Development (EOARD) 

Scalability of local and global instability and damage tolerance of honeycomb sandwich composite structures 

@ POLIMI

Sandwich structures add further complexity to the design and certification process of aerospace structures, as they are susceptible to several interacting failure mechanisms, that are largely influenced by their configuration and the type of load they are subjected to. In particular, a significant criticality has been identified in the face sheet/core debonding failure, where the lack of adhesion between the face sheet and the core can compromise the structural integrity of the sandwich structures.

The research project develops a numerical methodology for the prediction of global/local instabilities of honeycomb sandwich panels by recurring to finite element analysis whose results are validated by experimental testing on small scale samples. The developed methodology is then used to investigate a real case study, supporting full-scale testing that will be reduced to a minimum thanks to numerical models validated on small scale structures.

Funded by Leonardo Labs and PNRR (National Recovery and Resilience Plan financed by Next Generation EU)

Buckling of conical-cylindrical composite structures for launch-vehicles

@ TU Delft and POLIMI

Launch-vehicle shell structures, which can be comprised of both cylindrical and conical sections, are known to be susceptible to buckling due to their large radius-to-thickness ratios. Advancements in composite manufacturing and numerical methods have enabled designers to consider more nontraditional shapes, such as connecting the conical and cylindrical sections with a toroidal transition to create a single-piece conical-cylindrical shell. This single-piece construction eliminates the need for a stiff, heavy interface ring between sections and has the potential to reduce mass.

To make this unitized conical-cylindrical shape a common design solution, the research activity develops a methodology for the design and analysis, and performs experimental buckling tests on composite conical-cylindrical shells. In this way, the ability to predict the buckling response of composite-conical cylindrical shells using nonlinear finite element analyses is developed and aids in future design guidelines and recommendations for launch-vehicle shell structures of this geometry.

In collaboration with NASA Langley Research Center  and NASA Marshall Space Flight Center