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Title: The mechanical performance of adhesively bonded hydroxyapatite coatings
Author: Thompson, Jonathan Ian
ISNI:       0000 0001 3529 1379
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 1998
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The aim of this research was to evaluate the mechanical performance of such a coating, with special reference to the performance in conjunction with a carbon fibre reinforced epoxy (CFRE) substrate. The programme of experimental work focused principally on the fracture behaviour of the coatings and the coating/substrate interface. A substrate of either CFRE or titanium alloy was coated with up to three coatings: epoxy and epoxy filled with fine HAP particles for mechanical compatibility and coarse surface HAP particles for biocompatibility. Monotonic tests were carried out using wedge cleavage and endnotched flexure (ENF) specimens; fatigue test specimens were in the double cantilever beam or ENF configuration, in order that both mode I and mode II performances were evaluated. It was found that the fracture energy of the coated surface was always in excess of 100J/m², an order of magnitude higher than the fracture energy of plasma sprayed HAP coatings on a titanium alloy substrate. A carbon fibre reinforced epoxy substrate, with the three coatings as described above, had excellent fracture properties, and the presence of the HAP did not adversely affect performance. The loading mode had a large influence on crack path such that monotonic and fatigue cracks tended to deflect to follow a mode I crack path even if the specimen was loaded under mode II conditions. This led to crack growth along the fibre/epoxy interface in mode II, but predominantly adhesive failure in the coating in mode I. The mode II fracture and fatigue performance were superior to those in mode I. There was no adverse effect of exposure to Ringer's solution on the fracture properties of composite-based specimens, in contrast to specimens with a titanium alloy substrate, for which soaking in Ringer's solution reduced the fracture energy by 50%. However, the fatigue performance of specimens with CFRE substrates was affected at low ΔG, which may be attributed to residual shear stresses at the fibre/epoxy interface as a result of swelling following moisture uptake.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Biomaterials; Carbon fibre reinforced epoxy