Modular Infusion

: A multi-functional approach to liquid resin moulding

Abstract

Composite component manufacturers often select resin infusion processes as low-cost alternatives
to autoclave pre-preg manufacture particularly when fabricating larger components. However,
infusion processes are challenged by a lack of repeatability, which is exacerbated when component
size and complexity is increased. Furthermore, when composite structures suffer damage end users
often encounter costly repair or scrap decisions. Both high risk processing, as well as a lack of inservice repair options challenge a wider adoption of composites. Many current manufacture and
repair processes that are used are not sustainable, hence, have a negative impact on the
environment. In this thesis new methodologies for efficient resin infusion, repair and recyclability are
investigated that have the potential to create a paradigm shift in the composites sector.
An infusion approach is created that provides improved robustness gained by segmenting a structure
into discrete elements allowing predictable and preferential flow front propagation. Segmentation is
achieved through the targeted application of compaction of fibres in-plane and resin film barriers
out-of-plane. Additionally, resin film barriers are developed to provide a targeted interfacial repair
method enabling in-service repair as well as end of life breakdown options. Manufacturing trials,
non-destructive testing and mechanical testing are utilised to optimise modular infusion (MI)
approaches, as well as quantify the performance of the resulting composite structures.
It is demonstrated that MI methods reduce the evolution and severity of defects introduced by
infusion processes. Subsequent mechanical testing also demonstrated comparable properties were
achieved for both MI and baseline vacuum assisted resin transfer moulding (VARTM) components.
Moreover, barriers paired with optimised relaxation processing resulted in segregation of flow fronts
without a degradation in mechanical properties. Resin film barrier interfaces are shown to exhibit
more predictable failure modes and performance envelopes compared to VARTM baselines. Vitrimer
material formulations were also investigated, where thermal characterisation methods were
employed to develop a healable barrier film exhibiting excellent recovery of mechanical properties
after 3 healing cycles.
The work described in the thesis provides a pathway for the adoption of MI approaches that has the
potential to enhanced life cycles through the de-risking of manufacturing processes. Furthermore,
the introduction of vitrimers could facilitate in-service repair and disassembly at end of life, the latter
allowing for elements of the structure to be salvaged or more readily recycled. Many further
research opportunities arise from the work conducted within this thesis such as, multi-matrix
infusions, healable interface development, induction heating cycle development, design
considerations for resin barrier produced components and in field healing verification methods.

Date of Award	4 Feb 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	James Kratz (Supervisor) & Janice M Barton (Supervisor)