**PROJECT**: Fracture mechanics of brittle matrix composites

**SPONSOR: **Air Force Office of Scientific Research, Washington DC

**PRINCIPAL INVESTIGATORS**: Autar Kaw and Glen Besterfield

**DATES**: September 1992 – June 1995

**DESCRIPTION: **A basic study of the fracture mechanics of brittle matrix composites is proposed. Three analytical models for studying the fracture mechanics of brittle matrix composites will be developed. The solution will be based on two dimensional planar or three-dimensional axisymmetric conditions, linear elasticity and imperfect fiber-matrix interface conditions.

1) The first model will determine the effect of finite fiber volume fraction on the initiation of matrix cracking and damage mechanics of brittle matrix composites.

2) The second model is a basic comparative study of the results and conclusions drawn from solving fracture mechanics problems, such as concerning stress at which matrix cracks initiate and deflection of cracks at the interface, by using the planar and axisymmetric assumptions.

3) The third model will find the effect of imperfections in the interface in brittle matrix composites. The main emphasis will be to calculate the damage zones in the fiber-matrix interface and study its effect on the matrix crack initiation stress and the crack deflection criteria.

All the above models will be compared with other analytical models and experimental results available in the literature. On a parametric basis, the fracture and damage mechanics of a matrix crack will be studied as a function of the elastic moduli and the thermal expansion coefficients of the constituents, fiber volume fraction, operating temperatures, crack geometry, remote loading strains, and roughness of the interface.