Fracture of Ceramic-Polymer Composite Biomaterials

Fracture toughness, strength, and elastic modulus of poly(methyl methacrylate) (PMMA)and poly(buty1 methacrylate) (PBMA)-impregnated alumina ceramics were measured as a function of polymer volume fraction, mean polymer particle size, and interfacial bonding between the polymer and ceramic. Fracture toughness was found to increase with increasing polymer volume fraction and decreasing polymer particle size. Interfacial bonding played a very important role in determining the fracture mode, which was interparticle and intraparticle when the interface was coupled and uncoupled, respectively. Poly(methy1 methacrylate) increased the fracture toughness of the ceramic 1.5 to 2 times more effectively than poly(buty1 methacrylate). The elastic modulus was found to be unaffected by impregnation. The previously reported Bowie model was modified and proved to be useful. Singleand double-crack versions of this model predicted strengths somewhat higher than those measured. This discrepancy and the scatter in the data were explained by the crack-path tortuousity and the possibility of different mechanisms operating in different samples. Fractographs of the selected bend specimens were taken to support this argument.