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European industrial doctorate for advanced, lightweight and silent, multifunctional composite structures

Periodic Reporting for period 1 - N2N (European industrial doctorate for advanced, lightweight and silent, multifunctional composite structures)

Reporting period: 2018-03-01 to 2020-02-29

Modern aeronautical structures are increasingly made of composite materials due to their well-known benefits. Despite their superior structural characteristics, composite structures exhibit poor dynamic and acoustic isolation levels compared to conventional metallic ones. As a result and in order to maintain the comfort levels in the passenger
and payload compartments within acceptable limits, additional acoustic and vibrational isolation technologies (sound packages) are necessary in several transport applications. If non-optimally designed for a certain application, these sound packages can add substantial weight to the structure, compromising the weight benefits gained by the
employment of composites.

The aforementioned challenges imply an urgent and genuine need for development of lightweight and multifunctional structures, for modern industrial transport applications. The N2N Training Network aims at developing a high-fidelity and efficient Multidisciplinary Design Optimization (MDO) scheme for multifunctional composites having poroelastic inclusions and combining minimum mass with maximum damping and comfort levels.

On the research side, N2N will focus on developing multiscale models for obtaining a comprehensive description of random poroelastic materials coupled to a composite structural segment. Understanding the interaction of acoustic waves with such complex materials is another scientific challenge that the Network will tackle. N2N aims at
developing reliable tools for providing accurate optimal designs for multifunctional composite structures that combine lightweight properties with exceptional acoustic and vibration isolation.

On the training side, N2N will provide a fully supportive environment for 3 ESRs. A training programme aiming at developing both the research as well as the transferable skills of the Fellows has been designed. All Fellows will have the opportunity to work in a multidisciplinary (industrial and academic) research environments.
1. Multiscale aeroelastic modelling in porous composite structures

ESR1-A detailed review on micro and multi-scale methods on poromechanics applicable for foam materials and a functional finite element code was developed in MATLABB. This was submitted as the first deliverable of WP1.

Numerical validations were then subsequently performed for benchmark cases to confirm the veracity of developed numerical model.

Methods such as the CutFEM, Scaled Boundary Finite Element method (SBFEM), Isogeometric Analysis (IGA) and the Virtual Element Method (VEM) were reviewed in detail.

A working virtual element method code has been developed in MATLAB for simulating the mechanics and vibro-acoustic behaviours of solid and poro-elastic materials

2. Vibroacoustic performance modelling

ESR2- Sandwich composite structures exhibit high stiffness whilst being light-weight and are widely used in the transportation and construction industries. Multi-layer systems, similar to sandwich structures have diversity of materials, there is a necessity for equivalent plate models to be employed within Finite Element Modelling (FEM) to reduce the computational effort. On this front, an analytical expression of frequency limit of a thin plate model has been derived as the present equivalent plate models are following thin plate theory.

A simpler equivalent plate model has been developed for symmetric sandwich plates which produces the same result as the existing equivalent plate models. Further, an improved equivalent plate model has been developed which includes both symmetric and antisymmetic modes of the sandwich structures.

3. Design optimisation and experimental validation

ESR3-Within the framework of WP3, different metaheuristics have been used for the optimisation of porous sound-absorbing packages with the objective of maximizing the sound absorption coefficient.

Furthermore, comparisons on the performance of different solution representations and approaches to obtain improved algorithms for acoustic porous material optimisation are being considered. The task will be done in two steps, namely, material optimisation and shape optimisation.

All RP1 deliverables have been submitted.

All RP1 milestones have been attained on time.

All recruitment actions have been completed.
Communication and public engagement strategy of the project
The advances of N2N can have significant impact in increasing social awareness on modern aircraft safety as well as inspire the new generation of structural designers and vibroacoustics engineers. The following actions will be taken in order to ensure that the developments will be successfully communicated to the public:

UNOTT frequently participates in the two biggest European Airshows. All fellows will exhibit their work at the Farnborough International Airshow or the Paris Airshow having a stand dedicated to illustrating the N2N technologies. All ESRs will be involved in this activity.

Engagement with schools in UK and France: All ESRs will visit local schools (at least one each) to deliver a presentation on modern industrial structural design challenges and promote science and engineering education through their posters. In case no ESR speaks fluent French, this visit will be organised by MATELYS’ Dr. Luc Jaouen in Lyon.
Moreover, the ESRs will present their work at the annual UNOTT Faculty of Engineering Annual Christmas Lecture. The lecture is attended by 200 school children aged 12 -16 and is preceded by interactive stands in the Engineering and Science Learning Centre. Each fellow will showcase their research and communicate with the children about the merits of engineering education and aircraft safety awareness.

The optimally designed structural panels (principal part of the N2N technological demonstrator) will be employed (also after the end of the project) during Open UCAS days and school visits at UNOTT along with accompanying information on modern structural design challenges (weight, sound transmission, reliability etc.). Demonstrators along with accompanying informative posters and presentations have proved particularly efficient for inspiring and excite the curiosity of visitors in the developed technologies.

All ESRs will prepare two popular articles each, which will be published in ‘popular engineering webpages’ such as ‘’ and ‘’. The same articles will also be published online on N2N’s, UNOTT and MATELYS’ websites. These articles will popularize the developments to the non-expert public and will increase the awareness on modern structural design technologies.

A Linkedin network page will be created and will be frequently (every month) updated with N2N news. This will accelerate research impact and aid the profile of all ESRs for being ‘spotted’ by potential future employers.

Assisted by the graphic designing team of UNOTT, the ESRs will prepare a N2N movie illustrating in a form of cartoon, the challenge of designing multifunctional structures for specific industrial applications.
Mid-Term Review in Lyon April 2019