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The Effect of Surface Treatment on the Failure of Unidirectional Carbon Fibre / Epoxy Resin Composites.

Pickering, Kim Louise. (1993) The Effect of Surface Treatment on the Failure of Unidirectional Carbon Fibre / Epoxy Resin Composites. Doctoral thesis, University of Surrey (United Kingdom)..

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Tows of PAN-based carbon fibre treated to different levels of surface treatment have been impregnated with epoxy resin and tested in tension in order to study the effect of surface treatment on strength and failure mechanisms. This work forms part of one of the projects funded under the DTI-Link Structural Composites programme, entitled "Predict". The tensile strength of single fibres was found to be relatively insensitive to surface treatment. However, the tensile strength of impregnated bundles was found to decrease with increased fibre surface treatment for all of the impregnation resins studied. This is attributed to the increase in strength of the interface and consequent localisation of damage which is observed on increased surface treatment. The choice of impregnation resin was found to have a larger effect on impregnated tow strength than surface treatment. This effect is also considered to be mainly due to the change of the strength of the interface. Changes in the cure schedule were not found to significantly affect the strength of the composite, but were found to influence the failure mode of impregnated tows. Significant changes in strength were observed after "apparently minor" variations in formulation processing cycle. The strength of impregnated tows in hybrid samples was found to have a similar trend to those tested in air. Values of failure strain were found to be consistently higher at each surface treatment level than for those tested in air by approximately 7%, which is in agreement with the commonly observed "hybrid effect". These samples facilitated the study of failure mechanisms. Comparison of the number of fibre failures in an impregnated bundle that has been extended in tension with that predicted by the Weibull equation, shows very close agreement with the data obtained, suggesting that the fibres have a similar strength distribution in the composite as in air. Comparison of results with existing unidirectional composite failure models has highlighted the need for more precise information on the distribution of stress around fibre failures in order for further improvements on existing failure models to be made. Tensile tests of dry fibre bundles has been shown to have potential as a more convenient method for measurement of the strength distributions of fibres.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Pickering, Kim Louise.
Date : 1993
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1993.
Depositing User : EPrints Services
Date Deposited : 30 Apr 2019 08:07
Last Modified : 20 Aug 2019 15:31

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