Research Proposal: Distribution of defects and mode of failure for out of autoclave manufactured composite parts

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My interest in this project comes from my experience working with composite materials in Durham University Electric Motorsport. Most of the current solar car “Ortus” is constructed using pre-impregnated carbon fibre and Kevlar. Composite materials have been chosen as they have desirable material properties, parts with complex geometries can be produced and can be made strong in specific areas and directions while remaining lightweight. All the composite structural components, such as the chassis and the roll hoop, are designed and manufactured in Durham, using the vacuum bag method due to its lower cost compared to the autoclave method commonly used in industry.

The current solar car "Ortus" during manufacturing.

From my personal observation, manufacturing errors such as bridging in vacuum bags or insufficient vacuum pressure lead to the formation of voids, one of the main drawbacks with vacuum bag manufactured composites, as voids reduce mechanical strength. That leads me to wonder how much the presence of defects deviates the mechanical properties from what was predicted by using Finite Element Analysis(FEA).

This project will aim to investigate the relation between the formation and effect of defects in composite parts. Samples of composite parts will be laid up with defects intentionally introduced. The samples will be scanned using X-Ray Computer Tomography(XRCT) to characterize the defects. After which, the sample will be tested in tensile forces to destruction to determine the mode of failure. A relationship between the distribution of defects and the mode of failure will be established and a research paper will be produced to present the findings.

Owen Foo

Laidlaw Scholar

I'm a second-year engineer at Durham University. My main area for research is in composite materials, in particular the formation of voids and the effect of them. I'm also part of Durham University Electric Motorsport, we design, build and race a challenger solar car in the World Solar Challenge, a 3000km race held biannually in Australia!