Preparation and mechanical properties of short carbon fibers reinforced α-Al2O3-based composites

Abstract Short carbon fiber (C sf ) reinforced α-Al 2 O 3 (C sf /α-Al 2 O 3 ) composites were fabricated by a sol-gel dispersing method and a subsequent hot-pressing process. Effects of dispersing method, fiber contents and sintering aids on the mechanical performance of the composites were investigated. Based on sol-gel strategy, series of C sf /α-Al 2 O 3 composites were prepared and the C sf was evenly dispersed in the matrix of α-Al 2 O 3 and preserved its pristine smooth surface, much superior to that of C sf /α-Al 2 O 3 prepared using ball milling method where C sf was seriously damaged. The flexural strength of C sf /α-Al 2 O 3 composites first increase and reach the peak values, then decrease with the increase in fiber content. It reaches the maximum value of 336 MPa at 5 vol% of C sf , 106.0% higher than that of the α-Al 2 O 3 ceramic without C sf . The fracture toughness increases with C sf content and deliver the highest value of 7.1 MPa/m 2 at 15 vol% of C sf , 117.4% higher than that of the α-Al 2 O 3 ceramic without C sf (3.5 MPa/m 2 ). Fiber bridging, debonding and pulling out can effectively deflect the crack and release the stress intensity at the tip of the crack, resulting in the significant reinforcing and toughening effect in C sf /Al 2 O 3 composites. It should be mentioned that the tensile strength of the carbon fiber drastically decreases from about 2800 MPa to about 1200 MPa after heat-treated at 1500 ℃ for 1 h indicating that the potential of carbon fiber reinforcement is not fully exploited.