Interfacial Properties of C-Coated Alumina Fiber/Glass Matrix Fiber Composites

Abstract

C-coated alumina fiber/borosilicate glass matrix composites were fabricated by slurry infiltration and hot pressing. Composite flexural strengths were 118 MPa and 263 MPa for uncoated and coated fiber composites, respectively. The interfacial shear strength between the fiber and the matrix was measured by the indentation technique on in-situ fibers. Uncoated fiber composites were chemically bonded and mechanically weak and brittle. C-coated fiber composites showed tough fracture behavior, moderate strengths, and interfacial shear strength values of 107 MPa and 43 MPa for 20% and 45% fiber fraction composites, respectively. Fiber fracture surfaces showed no pulloutfor uncoated fibers, modest (30-60 μ) pullout for 20% fiber composites, and high pullout (>200 μ) for 45% fiber composites. Work of fracture measurements on coated and uncoated fiber composites showed that the work of fracture of uncoated fiber composites is the same as the unreinforced matrix. Coated fiber composites had much higher work of fracture and the values were dependent on fiber fraction. The interfacial shear strength, the fracture surface pullout lengths, and the work of fracture data were related to theory and were mutually consistent.