Analysis of a Ceramic Matrix Composite Flexure Specimen
Three-point and four-point flexure tests awre the commonly used strength and fracture toughness tests for brittle materials because of the simplicity of the technique and the ease with which the specimens can be fabricated. However, the formation of matrix cracks, single or multiple, on the tensile side of a ceramic matrix composite beam specimen destroys the macroscopic uniformity of the beam, and use of the flexure formula for bending stress calculations results in large errors. In this study, an analytical model is developed to give a more accurate prediction of the behavior of a unidirectional ceramic matrix composite beam exhibiting multiple matrix cracking. A combination of stress intensity factor and micromechanics approaches is employed in determining the failure modes, the true compressive and tensile stresses in the composite, and the shear stresses at the crack tip. The functional parameters are the applied load, beam geometry, and microstructural properties. The model predicts significantly different stresses than those obtained using the flexure formula.
L. R. Dharani, "Analysis of a Ceramic Matrix Composite Flexure Specimen," ASTM Special Technical Publication, American Society for Testing and Materials, Jan 1990.
ASTM Special Technical Publication (1990, Atlanta, GA, USA)
Mechanical and Aerospace Engineering
Article - Conference proceedings
© 1990 American Society for Testing and Materials, All rights reserved.
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