Prediction of the performance of structural power composites

Lead Research Organisation: Imperial College London
Department Name: Dept of Aeronautics


Structural multifunctional composite materials are a novel class of materials with the ability to perform various non-structural functions in addition to their structural role, for example, sensing and actuation, thermal and electrical transport, energy harvesting and storage, structural health monitoring and self-healing. The benefits of these technologies include improved reliability and lifetime, reduced component count, and reduced emissions in transport applications due to volume and weight saving and associated system level efficiency gains. Multifunctional composite materials and structures are presently drawing much attention in the aviation industry, where conventional structural composite technologies are now reaching maturity, and where it is recognised that emerging disruptive technologies, such as multifunctional materials, will be vital for future-proofing aircraft against increasingly stringent emissions goals. Adoption of these materials, however, implies a step change in engineering design philosophy and manufacturing practices, and a vast amount of research must first be undertaken to develop the material systems and technology frameworks.
On going research efforts led by Imperial College London focus on the development of multifunctional materials and devices which combine structural and electrochemical energy storage functionalities in the form of a structural supercapacitor. The devices are constructed as a hybrid fabric reinforced composite and employ unusual constituents such as carbon aerogel nano-reinforcement and a biphasic multifunctional matrix system, which pose unique implementation challenges. As is common in the field of multifunctional composites, development of the constituents and devices has been exclusively experimental. In these early stages of development total reliance on empirical research can be not only be time-consuming and expensive, but also impractical, since many of the constituents are still under development and therefore continually changing, and only limited quantities are available.
The focus of this PhD project is the development of computational finite element models to predict the performance of structural supercapacitors and to complement empirical research in the design and optimisation of the material for enhanced multifunctional performance. This is in line with the current shift across the engineering industry away from 'prototype and test' and towards 'model and simulate' design approaches. Establishing simulation tools which can accurately predict the mechanical and electrochemical behaviour of the material based on the properties of its constituents will assist in the identification of optimal material microstructures for specific applications, or vice versa, understanding the material's manufacturability and performance limits, and encourage the material's commercial adoption by demonstrating a predictable in-service response. Additionally, development of a multi-physics modelling framework to simulate the mechanical and electrochemical responses simultaneously will provide an integrated approach to multifunctional optimisation and means to investigate possible electro-mechanical coupling. To the author's knowledge there are no such published multi-physics modelling studies in either conventional supercapacitors, or structural supercapacitors, making the proposed work novel. The project is formed of two work packages. Work package 1 will focuses on development of realistic finite element models of the devices at meso-scale and prediction of elastic properties and damage initiation. Work package 2 will couple the mechanical model with an electrochemical model and establish a framework for multifunctional optimisation.


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Valkova M (2020) Predicting the compaction of hybrid multilayer woven composite reinforcement stacks in Composites Part A: Applied Science and Manufacturing

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509486/1 01/10/2016 30/09/2021
2091022 Studentship EP/N509486/1 01/10/2017 30/09/2021 Maria Valkova
Description I have been investigating the effect of the internal architecture of multifunctional electrochemical composite materials on their mechanical and electrical properties. This architecture is unusual, as it incorporates nanostructured carbon aerogel-modified carbon fibre fabrics, combined with thin glass fabric plies, in a hybridised laminate stacking sequence. Aerogel is used to simultaneously increase electrochemically available surface area, as well as composite mechanical properties by acting as a rigid interconnected network between the carbon fibres.

I generated new knowledge on several manufacturing and performance considerations related to the architecture of the carbon aerogel-modified carbon fabric. Firstly, compression experiments performed on the as-received and aerogel-modified carbon fabric revealed a significant decrease in the compressibility of the modified fabric, with implications to the fibre dominated mechanical properties of the later composites. This was due to the high compressive modulus of the carbon aerogel, which I characterised in nano-indentation experiments. I also identified the presence of defects in the aerogel-modified fabric architecture, introduced as a bi-product of the modification process, and demonstrated through finite element simulations their detrimental effect on the elastic mechanical properties of the composite. This highlighted a need to improve manufacturing methods to minimise the defects, and has additionally opened up important new questions regarding the effect of modification on the electrical conductivity of the fabrics (this is an important parameter for electrochemical performance).

I developed a consolidation simulation tool for the hybrid stacking sequences used in the multifunctional composites. The simulation results suggested a significant degree of variability in the fibre content and internal morphology of the hybrid multifunctional composite, introduced during the hand layup of the laminate. This variability is expected to be more significant for multifunctional electrochemical composites, as they are assembled by a method that differs from conventional composite manufacture methods (laminating individually-manufactured three-ply-thick cells instead of a one-step lamination of a large number of plies).

Finally, the consolidation simulation results were used in the development of composite unit cell models of the structural supercapacitors, which are currently being used for further mechanical analysis. Meanwhile, steps have been taken to extending the simulations to include electrical and electrochemical effects.
Exploitation Route Outcomes regarding the effect of defects in aerogel-modified carbon fabrics can be taken forward in the (re-)development of existing and alternative manufacturing procedures. Regarding consolidation problems, spread tow fabric architectures are already being pursued, which are less sensitive to the consolidation and variability issues.

The compaction simulation tool for hybrid fabric stacking sequences can be put to use by others investigating hybrid fabric composites for conventional structural applications, such as ballistic protection, in addition to its current use in mechanical modelling of multifunctional composites.

Future outcomes related to multi-physics modelling of the multifunctional composite are anticipated to have significant impact on the development and design of these materials, as detailed in the project abstract.
Sectors Aerospace, Defence and Marine,Electronics,Energy,Manufacturing, including Industrial Biotechology,Transport