This thesis is divided into six chapters. The first chapter
provides a brief introduction concerning the behaviour of brittle
materials. It also contains the justification for the undertaking of
the study as well as a brief description of the method of approach
adopted, and thesis layout. Chapter two provides a critical review of
the current literature available at present in the failure prediction
brittle materials. Both theoretical and experimental studies are
discussed and the relevance to the present work is justified. Chapter three deals with the numerical analyses adopted within
the thesis. Five different failure criteria were utilized in the
initial analysis of the results presented. Among them, the empirical
model using the Principle of Independent Action satisfactorily
represents the biaxial fracture behaviour of brittle materials in
both tension-tension and tension-compression quadrants. Its validity
has never been tested before. Various statistical fracture models
were used to analyze the failure of brittle materials under multiaxial
states of stress, the experimental failure data for simple tension
being a starting point for their calculation. It was shown that the
Energy Density theory led to a better agreement with the experiments
than any other well-known fracture criterion. The study investigates
methods of evaluating the Weibull parameters which were crucial in the
failure prediction of brittle materials. Monte Carlo simulation
techniques are also presented as a method of evaluating the data
ranking for the failure probability of brittle materials. Chapter four is devoted to the description of experimental
techniques adopted in the study, using specially designed rigs. Six
different tests were conducted to evaluate the performance of brittle
materials in static loading and also to enable comparisons with the
theoretical predictions. Attention was given to specimen casting,
loading frames, alignment, measurement techniques and other relevant
parameters. The use of the linear elastic fracture mechanics method
to predict the behaviour of cracks in bodies, which are subjected to
steady stresses, is discussed. The compliance function for the
three-point notch bend specimen is presented in addition to the
determination of the fracture toughness of Herculite LX plaster. The work was also supplemented by the use of scanning electron microscopy
(SEM) to failure analysis of plaster material. This is an extremely
important tool in the study of brittle materials since the dimensions
of small defects and fracture features on individual grains are often
pertinent information to the failure analysis.
Chapter five details the analysis of the theoretical results as
well as the experimental findings. Based upon the previously
mentioned approaches, a comparison was made between theoretically
predicted and experimentally observed data. The comparison indicates
that discrepancies exist between the observed and predicted results,
the reasons for the discrepancies have been justified in this work.
Chapter six provides a brief summary of conclusions derived from
the complete study, together with recommendations for future work
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