An experimental investigation of stiffness reduction and cracks geometry in a unidirectional brittle matrix composite

The nonlinear mechanical behavior of a unidirectional ceramic matrix composite is investigated by means of an ultrasonic method. This paper presents measurements of all the stiffness tensor coefficients during each step of a tensile test, and consequently the variation of all the components of the anisotropic damage tenser. A description in terms of compliance makes possible comparison between mechanical and ultrasonic measurements of the composite deterioration and the re-construction of the stress-strain curve from ultrasonic data. Good agreement between both experimental and predicted compliances of an anisotropic medium with distributed slit cracks is found. From this comparison, the crack density parameter is estimated and the matrix cracks geometry is characterized.