Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SAFE-FLY (European industrial doctorate for damage modelling and online detection in aerospace composite structures)

Teaser

Modern aeronautical structures are increasingly made of composite layered materials due to their well-known benefits. Composite structures however may exhibit a great variety of structural failure scenarios. Delamination, Fibre Breakage, Matrix Cracking and Debonding are the...

Summary

Modern aeronautical structures are increasingly made of composite layered materials due to their well-known benefits. Composite structures however may exhibit a great variety of structural failure scenarios. Delamination, Fibre Breakage, Matrix Cracking and Debonding are the most commonly occurring failure modes. Certain aircraft parts are more susceptible to specific damage types (e.g. the lower part of the fuselage is more vulnerable to buckling induced deformations, while the upper is more susceptible to cracks) and have to be regularly inspected. Moreover, composite structures are prone to extensive moisture absorption due to their porosity, while their mechanical behaviour can also present significant fluctuations due to temperature variations during the operational cycle. Modelling and damage identification within a structure with such a complex mechanical behaviour is a challenging task. Accurate modelling of damage requires a fine level of detailing at the component level. This results in large order numerical models that are computationally taxing. Fast, yet accurate multiscale modelling techniques can significantly enhance decision strategies and maintenance policies.

The aforementioned challenges imply an urgent and genuine need for development of reliable, accurate and lightweight systems for online structural integrity inspection in modern aeronautical structures. The SAFE-FLY Training Network aims on introducing a high fidelity/ low cost damage identification procedure for aircraft components. SAFE-FLY will deliver valuable, original technological tools for satisfying the industrial needs by focusing on:
• The development of novel, accurate mathematical descriptions for modelling the failure modes that can occur within composite structural segments.
• Development of novel methodological approaches for identifying damage in composite layered segments by means of ultrasonic guided waves (GWs).

SAFE-FLY is expected to deliver a new methodology for modelling and detecting damage within modern composite aerospace panels. This will be achieved by developing original numerical tools related to damage modelling as well as to GWs propagation and interaction. An industrial technological demonstrator incorporating all scientific breakthroughs will be delivered and will serve as a new benchmark for GWs based damage detection in the aeronautical industry. This will be facilitated by the participation of SAFE-FLY in the EC Open Research Data pilot scheme. Faster and more accurate identification of structural failure will be made possible on-the-fly, implying:
• Increase of the awareness on structural integrity for the pilot and the engineers.
• Increase of the availability of the aircraft.
• Decrease of the inspection related aircraft’s cost with simultaneous financial benefits for the operator and/or the passengers.

Work performed

The ESRs have advanced their research programmes, especially through performing an extensive literature survey on their projects. More specifically the general research progress of the Network is summarised below:

• A detailed review on damage modelling methods applicable for layered composites has been submitted as the first deliverable of WP1.
• A functional finite element code has been developed in MATLAB for formulating mechanics of shell elements, which are primarily used to model thin composite laminates. These formulations have been extended to model intra-laminar brittle cracks in composites using phase-field approach.
• Numerical validations have been subsequently performed for benchmark cases to confirm the veracity of developed numerical model. To cater to practical industrial requirements pertaining to damage modelling in aircraft structures, Abaqus subroutines for phase-field model are currently being developed which would be more scalable and suitable for solving large-scale problems.
• A detailed review on wave modelling methods applicable for layered composites has been submitted as the first deliverable of WP2.
• An extensive literature review on optimal sensor placement for guided wave-based SHM and probabilistic (Bayesian) methodologies has been performed. In addition, a novel methodology in this regard to take into account uncertainties coming from different sources, such as material or sensors, has already been proposed and it is under development.
• Furthermore, experimental work is being carried out in order to develop new industrial SHM products and post-processing algorithms.

All Year 1 SAFE-FLY deliverables have been submitted.

All relative Year 1 milestones have been attained on time.

All recruitment actions have been completed.

Final results

The SAFE-FLY project builds on the seamless interaction of three Early Stage Researchers (ESRs) aiming to fuse advanced computational methods for rapid yet accurate modelling with state-of-the-art structural health monitoring methods complying with the digital twins paradigm. The overarching objective is to provide a holistic approach towards damage identification of aerospace structures.

Within this setting, ESR1 is working on multiscale damage modelling of aerospace composite structures developing novel shell element formulations incorporating phase field modelling for damage simulation. ESR2 develops advanced tools for fast and efficient simulation of ultrasonic guided waves in composite structures. These tools will also incorporate algorithms for simulating the interaction of guided waves with damage in composite structures for localisation and characterization purposes; this aspect will be fed from ESR1 outputs. ESR3 addresses the optimal configuration of ultrasonic guided waves-based SHM. All the steps in the SHM challenge: (1) pre-configuration, (2) damage detection, (3) damage localisation, (4) damage identification, and (5) damage prognosis are covered in this project. To this end, probabilistic-based methodologies are under development to rigorously address the SHM problem by accounting for different sources of uncertainty.

It is anticipated that SAFE-FLY will advance the current state of the art for towards fulfilling the overarching objective of providing lighter, durable and safer aerospace structures hence realizing the EU objective for greener and reliable transport. Besides the primary mission of the SAFE-FLY project, it is anticipated that its outputs advance current state-of-the-art in i) computational modelling of composites structures, ii) simulation of guided waves and characterisation of damage, and iii) Optimal sensor configuration in ultrasound-based damage identification.

Website & more info

More info: https://safe-fly.eu/.