Skip to main content

Composite from a REsin PErspective

Periodic Reporting for period 1 - CREPE (Composite from a REsin PErspective)

Reporting period: 2018-05-01 to 2020-04-30

This project was focused on understanding the important role the matrix plays in a fibre reinforced composite. Most composites research focuses on the fibres, important as there are in imparting high specific stiffness and strength to the final material. However, the matrix, which bind the fibres together is equally as important and presents opportunities for tailoring the mechanics and performance to achieve unique and optimal behaviours.

The specific objectives outlined at the outset of this Fellowship were as follows:
• To understand the effects of molecular dispersity on the mechanical and fracture behaviour of epoxy polymers.
• To use this understanding to design next-generation thermoset epoxy polymers
• To understand the effects of nanoparticulate additives on the functional behaviours of epoxy based nanocomposites.
• To understand and improve the role of material processing on the final properties of the composite.
• To experimentally verify theoretical and numerical predictions and to manufacture ‘proof of technology’ components.
• To disseminate research findings internationally.

Following the conclusion of this Fellowship, It was shown that physical raging of toughened epoxy polymers was detrimental to the overall behaviour. This, is the single most important result from this work and has important implications in the aerospace, where thermal cycling of critical structural components may have a drastically reduced resistance to fracture after a number of years of service. To create a truly sustainable composite sector in the EU, it is proposed to translate the findings of this Fellowship into resins and polymers manufactured from renewable feedstocks.
Furthermore, it was also demonstrated as a result of work carried out during this Fellowship that the method of manufacture can also play a significant role in determining the final properties of the composite material. It is proposed as an avenue of future research that this be investigated further with a view to alleviating the detrimental effects that physical aging has on toughened epoxy polymers.
• The main results from this Fellowship are as follows:
o The rate at which the toughened epoxy polymers are cured in the bulk has a significant and detrimental effect on the achievable toughness via nano-modification.
o This detrimental effect is also noticeable when these toughened epoxy polymers are used as the matrix of fibre reinforced polymer composites.
o The molecular makeup of the epoxy polymer, be it a blended mixture of multiple resin and curative components or a simple two-component system has a significant effect on the resultant morphology of toughened polymers that form via Reaction Induced Phase Separation (RIPS). Moreover, the effect of confinement, on the resultant morphology has been investigated and shown in two separate composite systems that the onset of a co-continuous morphology can be affected by geometrical confinement.
o I have demonstrated that the effect of physical ageing massively reduces the toughness of toughened epoxy polymers over time. This has particularly serious implications for the aerospace industry, where the end-of-life toughness can be as much as one half of the designed material toughness. Moreover, I have extended existing predictive models to demonstrate that this end of life toughness can be predicted with some accuracy and suggest that this value be used as a design criterion.
o I have developed a numerical framework for modelling the failure of densely packed particulate composites that can directly account for inherent variability in the experiment.

A total of three journal articles have been accepted and published din leading international journals with an additional three article sin the final stages of preparation. Nine conference papers have ben presented at a variety of international conferences enhancing the impact of the science.
The work done in this Fellowship has advanced the knowledge of polymers and polymer composites. We now have a greater understanding that the method of manufacture can play a very important role in defining the final properties of the materials. This was largely deemed irrelevant before. The company with whom I carried out this fellowship now implement this knowledge to their designs.

A large step beyond the state of the art was achieved when considering how toughened polymers degrade over time. I have linked the degradation in toughness to the loss of pressure sensitivity in the polymer matrix.