Fabrication and characterisation of composites based on a DGEBA epoxy reinforced with as received Australian fly ash

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Copyright: Ibraheem, Shahad
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Abstract
Fly ash (FA) is a ‘waste’ by-product from coal thermal power stations. FA consists of a wide range of ceramic materials as well some unburnt carbon (loss on ignition LOI) – so FA is useful as a filler material to improve mechanical properties of polymers, reduce cost of product and get light weight composites. In this thesis, an Australian FA, in as received condition, and without any surface treatment, has been used as reinforcement in a DGEBA epoxy matrix with 0, 10, 20, 30, 40, 50 weight precent FA. Curing temperature of the composites was 120 C for 2 hours. Mechanical testing showed that particularly with 10 % FA addition yield strength increased by 60 %. Increased FA content reduced strain to failure, from 35 % for the neat epoxy to 4 % for 10 % FA-epoxy, and 2 % for 50 % FA-epoxy. The 40 % FA-epoxy composites showed a high ductility, over 18%. Vickers micro-hardness studies indicated that the microhardness was higher at 300 gm load whereas it decreased and became steady at 500g and 1 Kg loads. In scanning electron microscopy (SEM) studies, fracture surfaces of all the FA – epoxy composites showed mainly homogenous but some clustered distribution of FA. There is general evidence of FA debonding and pull out of the matrix indicating adhesion in composites and overall energy absorption. There are examples of matrix strongly adhering to FA. To understand interaction between filler and polymer matrix, Fourier transform infrared spectroscopy (FTIR) for raw fly ash, pure epoxy and 40% fly ash-epoxy composite showed that a few functional groups in fly ash actively interacted with epoxy. SIMS (Secondary ion mass spectrometry) analysis, supportive EDS (energy dispersive x-ray spectroscopy) & SEM study of the as fabricated surfaces of 3 composites (10%, 20% and 50% FA) were undertaken to obtain i) trace levels of FA elements, ii)) information regarding lateral distributions of these elements in the composites, and c) study the micro-crack features on the bombarded surfaces. There was in general qualitative matching with the fractography SEM micrographs Finally, a limited work was undertaken to study the possibility of reducing the size of the FA by using conventional ball milling. On average, ball-milling reduced the particle size by approximately 50%. X Ray Diffraction peaks of the ball-milled FA showed evidence of some line broadening, possibly due to residual stress caused by the grinding process.
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Author(s)
Ibraheem, Shahad
Supervisor(s)
Bandyopadhyay, Sri
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Publication Year
2013
Resource Type
Thesis
Degree Type
Masters Thesis
UNSW Faculty
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