One size doesn't fit all

: An approach to progress delivery of sustainability for the composites industry

Abstract

The habitat which we as humans call home is changing as a result of our actions.
Decades of un-checked economic growth starting with the industrial revolution
are damaging the planet. As engineers and scientists, we have the capability to
reduce the impact humankind is having and move towards a sustainable or even better, regenerative lifestyle. Composite materials with their energy intensive productive methods, complicated
end of life processing and wasteful manufacturing processes have hurdles to overcome in reducing
their environmental impact. The challenge of sustainability lies in how to quantify what drives
a given design to be sustainable and does it forgo functional performance or imply significant
financial cost in being so.
Life Cycle Engineering (LCE) is a means of assessing the performance of designs or materials, considering the whole life cycle, against economic, environmental and technical factors. It
has seen relatively little application to composites case studies, especially for marine industry.
Furthermore, iterative design approaches that move beyond simple materials selection diagrams,
instead utilising for instance optimisation algorithms, have been seldom seen. This thesis first
implemented an algorithm which embodies LCE to enable quantification of a given application’s
holistic performance against economic, environmental and technical criteria. The Particle Swarm
Optimisation (PSO) algorithm implemented methods from work found within literature which
were combined to allow for both discrete and continuous variables to be used. The Pareto front, a
set of non-dominated solutions, was subject to a selection process to then arrive at a single design
for a set of subjective weighting criteria. This process allowed for an optimised design to be found,
for a given application and set of subjective weighting criteria.
Materials were selected to build a database to assess the three LCE criteria. Glass, basalt
and flax fibres were selected with epoxy, bio-epoxy and Elium® resins. The selected materials
were characterised to generate the required data against economic, environmental and technical
factors. Economically, on a per kg basis glass composites had the lowest life cycle cost, followed
by basalt and finally flax. Environmentally, on a per kg basis, basalt and Elium® had the lowest
environmental impact, due to the low impact of fibre production and the low energy requirement
during the manufacturing process. Flax and epoxy was found to have highest environmental
impact, due to the high impacts associated with the spinning of flax fibres and the high energy
requirement from production of epoxy constituents. Technically, at approximately the same areal
weights, basalt fibre composites had a significantly higher tensile stiffness and strength than
glass and even more so than flax. In shear testing, glass composites were superior, with basalt
close behind and flax the lowest.
The data was then used to design and manufacture a marine industry demonstrator. Using
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the previously generated data, with the algorithm previously mentioned, it was found that basalt
and Elium® was the optimised solution when environmental and technical factors are given preference over economic factors. Glass and epoxy was the choice for a ’business-as-usual’ scenario,
where economic and technical factors are preferred to environmental considerations. Basalt composites dominated the design space where economic factors were not given significant weighting,
with glass composites dominating the space where they were. The two sandwich structures, which
at a high-level attempted to replicate a Rigid Inflatable Boat (RIB) transom, were manufactured,
using basalt and InfuGreen810 and glass and epoxy to manufacture symmetric facings, adhered
to a foam core. The tests showed good agreement with the analytical and numerical predictions
that were carried out.
This work demonstrated that, for one application, basalt composites are the optimised solution where environmental factors are prioritised, something necessitated by the current climate
emergency. Furthermore, it has demonstrated a methodology which should be used for assessing
what the most ’sustainable’ solution is for further applications. The work represents a first step
in what will hopefully instigate further work assessing what is the most sustainable design for a
plethora of other case studies. For only if such case studies are considered, will there be truth
around what forms designs must take to tackle the climate crisis.

Date of Award	18 Jun 2024
Original language	English
Awarding Institution	University of Bristol
Supervisor	Richard S Trask (Supervisor), Ian Hamerton (Supervisor) & Marco L Longana (Supervisor)