Towards creating multi-matrix continuous fibre polymer composites using an out-of-vacuum bag process

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Conventional fibre polymer composite materials consist of a single matrix system for a whole part and are selected on the dominant requirements of the part. A multi-matrix composite would provide an expanded design space for a composite part. However, there are few processes available to realise such a composite and these rely on modified forms of resin transfer moulding. These processes require active venting using an expensive vacuum system and the quality is reliant on bag quality. This research is devoted to developing a foundational principle for a processing strategy that uses the localised introduction of resin combined with an out-of-bag consolidation process containing a preheating stage that can form a multi-matrix composite.
The resin flow in local deposition and consolidation processes is determined by a complex interplay between the resin and preform. Hence the chosen resin and fabric were characterised extensively. A range of viscosity-tailored consolidation schemes was implemented using a setup to estimate the in-line viscosity using the rheo-kinetics of the fast-curing resin system. By initiating the consolidation pressure at a higher resin viscosity, the voids were found to be suppressed. A simplified model to capture the dominant mechanisms during consolidation was developed. The dominant flow transitioned from a 2D yarn-scale to macro-scale flow on increasing the activation viscosity. The increased resin pressure associated with high resin viscosity during consolidation was found to be a dominating factor in reducing the voids. The model was then used to develop a simple analytical design tool for tailoring the consolidation parameters to minimise the void content. A feasibility study was conducted on combining different matrices to improve the mechanical performance of composites in an open hole tension test. The use of high stiffness carbon nanotube modified resin to locally manipulate the region around the hole increased the strength of the composite. The enhancement of multi-matrix composite was then qualitatively explained using a simple finite element analysis combined with classical laminate theory.
Date of Award25 Jan 2022
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorDmitry Ivanov (Supervisor), Ian Hamerton (Supervisor), Fabrizio Scarpa (Supervisor) & Milo Shaffer (Supervisor)

Keywords

  • Composite materials
  • Manufacturing
  • Multi-functional composites
  • Additive manufacturing
  • Liquid Resin Printing

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