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Development of a thermally-assisted piercing (TAP) process for introducing holes into thermoplastic composites.

Brown, Nicholas W. (2016) Development of a thermally-assisted piercing (TAP) process for introducing holes into thermoplastic composites. Doctoral thesis, University of Surrey.

Nicholas Brown Engineering Doctoral Thesis - May 2016.pdf - Version of Record
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Composite parts can be manufactured to near-net shape with minimum wastage of material; however, there is almost always a need for further machining. The most common post-manufacture machining operations for composite materials are to create holes for assembly. This thesis presents and discusses a thermally-assisted piercing process that can be used as a technique for introducing holes into thermoplastic composites. The thermally-assisted piercing process heats up, and locally melts, thermoplastic composites to allow material to be displaced around a hole, rather than cutting them out from the structure. This investigation was concerned with how the variation of piercing process parameters (such as the size of the heated area, the temperature of the laminate prior to piercing and the geometry of the piercing spike) changed the material microstructure within carbon fibre/Polyetheretherketone (PEEK) laminates. The variation of process parameters was found to significantly affect the formation of resin rich regions, voids and the fibre volume fraction in the material surrounding the hole. Mechanical testing (using open-hole tension, open-hole compression, plain-pin bearing and bolted bearing tests) showed that the microstructural features created during piercing were having significant influence over the resulting mechanical performance of specimens. By optimising the process parameters strength improvements of up to 11% and 21% were found for pierced specimens when compared with drilled specimens for open-hole tension and compression loading, respectively. For plain-pin and bolted bearing tests, maximum strengths of 77% and 85%, respectively, were achieved when compared with drilled holes. Improvements in first failure force (by 10%) and the stress at 4% hole elongation (by 18%), however, were measured for the bolted bearing tests when compared to drilled specimens. The overall performance of pierced specimens in an industrially relevant application ultimately depends on the properties required for that specific scenario. The results within this thesis show that the piercing technique could be used as a direct replacement to drilling depending on this application.

Item Type: Thesis (Doctoral)
Subjects : Composite machining
Divisions : Theses
Authors :
Brown, Nicholas
Date : 30 June 2016
Funders : TWI Ltd., EPSRC (EP/G037388/1)
Grant Title : EPSRC EngD Studentship
Copyright Disclaimer : TWI Ltd. retains the copyright for all images within this thesis. Images should not be reproduced or shared without prior written permission.
Contributors :
ContributionNameEmailORCID, S.L., P.A., C.M.
Depositing User : Nicholas Brown
Date Deposited : 12 Jul 2016 08:47
Last Modified : 11 Dec 2018 11:22

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