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Title: On the relationship between layup time, material properties and mould geometry in the manufacture of composite components
Author: Bloom, Leo Dominic
ISNI:       0000 0004 5918 1934
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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The work in this thesis aims to contribute to the understanding of the hand layup process. To date, this method of manufacture has no viable competition in terms of the complexity and quality of the parts which can be made. Despite its widespread use, the existing knowledge is dominated by rule of thumb approaches and the literature lacks detailed studies specifically aimed at understanding and delivering improvements to the existing process. The fact that laminators can express a preference for working with certain prepregs prompted an investigation into the properties which contribute to 'drapability' and influence laminator perceptions. However , since there are no standard tests for evaluating prepreg formability, a characterisation scheme for measuring the relevant properties, namely shear behaviour , tack and flexural rigidity, has been devised. These properties are then correlated with the layup performance of the prepregs, as measured by observing and timing professional laminators laying up over a series of representative geometries. Layup time is proposed as an objective measure of difficulty, which also correlates well with laminators' subjective ratings. A relationship between material properties, mould geometry and layup time is then derived, suggesting that it is possible to predict layup time from a knowledge of mould geometry and material properties. Techniques to further characterise prepreg behaviour are then considered. Digita1 Image Correlation is explored as a way of investigating the deformation mechanisms and out of plane behaviour of spread tow prepregs. A high resolution pressure sensor is also used to measure the forces applied during layup, to understand how these might vary with the amount of shear deformation introduced into the prepreg and with the choice of material system. This is another example of how the human factors involved in hand layup are addressed in a novel way. With an understanding of the factors which contribute to difficulty, it is proposed t hat important productivity increases can be delivered without significant changes to the existing process. For example, by simply choosing a different material, layup times can be halved, and similar reductions in labour content can be achieved by varying the mould geometry.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available