Daniel, Adrian Matthew (1994) Interfacial properties of fibre reinforced ceramic matrix composites. PhD thesis, University of Warwick.

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Abstract

A review of ceramic matrix composites development over the past thirty
years is presented, with emphasis placed on their application in gas turbine engine
components.
The fracture mechanics of brittle solids are outlined and the toughening
mechanisms operating within continuous fibre reinforced ceramic matrix composites
are discussed. The importance of the fibre-matrix interface in governing the overall
mechanical properties of a composite is highlighted with respect to the
micromechanical properties of interface debond fracture surface energy OJ and
frictional shear stress t.
Current techniques for measuring OJ and t are listed, together with their
inherent disadvantages. The requirement for a micro-indentation system that can be
used to measure interfacial properties via individual fibre pushing experiments across a
wide range of composite systems, is discussed.
The development of a unique Scanning Electron Microscope (SEM) based
microindentation system is described in detail. It enables dynamic, high magnification
imaging of the indentor tip and specimen contact point, and continuously records
applied load and tip displacement throughout the indentation cycle. A piezoelectric load
cell, coupled to a specifically developed amplifier, enables load resolution of 2mN
measured up to the maximum possible of 20N. Novel capacitance displacement gauge
design gives a resolution of lOnm over a l00pm range.
The instrument has been used successfully to measure the interface
micromechanical properties across a wide range of silicon carbide fibre reinforced glass
and glass ceramic matrix composites. This data has been correlated with interface
structural information obtained via Transmission Electron Microscopy (TEM) and
SEM. Effects of oxidation, fatigue testing and interface pre-synthesis via fibre coating,
have been measured. Fibres with diameters ranging from 7JJ;mto 150pm have been
tested to demonstrate the versatility of the device for interfacial property measurement
across the full range of modem ceramic matrix composites. Successful attempts have
been made to correlate changes in the interfacial OJ and t to changes in overall
composite mechanical behaviour. Theoretical requirements for values of G, that
introduce toughness to composites have been discussed and compared to those
determined by experiment. Variation of t and its effect on matrix micro-cracking and
the tough!brittle property transition of a composite has been measured.
Other applications that exploit the instrument's high resolution and imaging
capability have been demonstrated. They include hardness and modulus measurement
of individual phases in heterogeneous materials, and direct observation of controlled
crack growth in ceramic composites.
Ideas for the development of the instrument into a more versatile SEM
based mechanical test facility are proposed.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics T Technology > TA Engineering (General). Civil engineering (General)
Library of Congress Subject Headings (LCSH):	Ceramic-matrix composites, Fiber-reinforced ceramics, Transmission electron microscopy
Official Date:	November 1994
Dates:	Date Event November 1994 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Lewis, Mike
Extent:	viii, 217 pages
Language:	eng

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