EFFECT OF CARBONISATION ON PANOX PREFORMS FOR COMPOSITE REINFORCEMENT

Abstract

The use of carbon fibres as a reinforcement for composite materials has significantly increased in recent decades. They find their major applications as high-strength materials, mainly in the aerospace and automotive sectors; however, due to their high manufacturing cost, their employment is limited. Currently, carbon fibre reinforced composites production remains a laborious and expensive process. The aim of this research is to investigate an alternative manufacturing method that can lead to more economical and straightforward formation of carbon fibre reinforced composites and to use analytical methods for the prediction and validation of ultimate mechanical properties. In this research, a predictive model, previously developed in the group, was adopted for predicting pre-carbonised and post-carbonised PANOX tensile properties. A sensitivity study was conducted in order to validate and characterise the most dominant yarn and tensile test parameters for the generation of an effective estimating fabric stress-strain curve. The investigation was based on one hundred parameter variations, and it allowed a selection of the most controlling properties, which were found to be the yarn testing gauge length, the fabric sett, and the yarn tensile strength; these were then subjected to a selection of different variations and the results were examined. In particular, the testing gauge length parameter was found to be one of the most significant and influencing factors in the study; for this reason, part of the research focussed on the development of mathematical equations able to describe the importance and impact of the yarn segment length in contact with curved capstan grips. The finding allowed the introduction of corrections that, when applied to the analysis of data, led to a yarn stiffness increase. This resulted into a more accurate correlation between experimental results and model predicted results. Once the dominant testing criteria were identified, a strength transfer evolution study between pre-carbonised and post-carbonised materials was set up at different textile levels (single filament, yarn, fabric preform, and reinforced composite). The investigation revealed the effects of carbonisation and structure morphological changes on the ultimate tensile properties of PANOX. One of the objectives of the thesis was also to investigate alternative testing methods for the determination of single fibre tensile properties, in order to facilitate the preparation of individual specimens. The zero gauge length study has shown that by testing pre-carbonised yarns at the minimum possible gauge length, and by knowing the amount of single filaments composting the yarn, it is possible to derive the ultimate tensile properties of single fibres. The study was then repeated on post-carbonised yarns for the determination of single fibres strength properties, and the results were then compared with single fibres tensile data obtained from standard tests. The outcome allowed the identification of testing parameters that would produce results comparable with standard single fibre properties. This finding can significantly simplify the single filament sample preparation procedure and time. Finally, pre-carbonised and post-carbonised materials were tested at each composing stage; the results have shown the differences in tensile properties between pre-carbonised and post-carbonised fibres, yarns, and fabrics. Ultimately, the comparison of PANOX reinforced composites reinforced by pre-carbonised and post-carbonised PANOX showed a considerable strength increase. This result demonstrated how this alternative manufacturing approach could diminish the amount of production wastes and costs.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Venkata Potluri (Supervisor)