The development of a novel multi-scale modelling framework to predict the effect of porosity on the transverse strength of fibre reinforced polymer composites

Fisher, Benjamin 2024. The development of a novel multi-scale modelling framework to predict the effect of porosity on the transverse strength of fibre reinforced polymer composites. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The use of composites in automotive applications is fast becoming prevalent due to increasing requirements for low-emission vehicles and the extension of the electric vehicle range. A main obstacle in the wide application of composites is a plethora of manufacturing-induced defects. Currently, more work is still required to accurately predict the exact material response for different defects. One of the most significant manufacturing defects is the inclusion of porosity, it is almost impossible to completely mitigate and if not controlled or accounted for properly, can have a catastrophic impact on structural composites. Previous work has attempted to address this issue; however, for the most part, it has only focused on the void content as the main contributing factor in degrading the material properties. Recent studies have since found that the shape and size of the porosity also have an important role in determining the response. This thesis focuses on developing a design tool to predict the effect of porosity in unidirectional carbon fibre reinforced polymer composites. The main output from this project is a modelling framework which can account for accurate porosity parameters, including void content, shape, and size. The modelling framework achieves this by splitting the procedure into two distinct stages; first, studying how voids knock down the strength of neat matrix and second, the ‘knocked-down’ matrix strength is used in a Representative Unit Cell to predict ply properties. The modelling process was conceptualised and used to study the correlation between the void parameters and the matrix strength. Observations were established on how voids act as stress raisers on the surrounding material and comparisons were investigated using a representative analytical model. An experimental campaign was undertaken whereby laminates were manufactured through prepreg/autoclave procedures as well as through resin infusion, using various methods to vary the porosity. The laminates were mechanically tested, and the porosity parameters were characterised. The porosity characterisation data was subsequently used to build representative models which were correlated to the empirical testing.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Engineering
Uncontrolled Keywords:	1) Composites 2) Finite Element Analysis 3) Multi-Scale Modelling 4) Porosity/Voids 5) ABAQUS 6) Empirical Testing
Date of First Compliant Deposit:	24 April 2024
Last Modified:	24 Apr 2024 09:54
URI:	https://orca.cardiff.ac.uk/id/eprint/168220

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