The adhesive strength of a thermophysical bond between two polymers has been examined using fracture mechanics. Bimaterial composite specimens were constructed by injecting C fiber polyetheretherketone (PEEK) into a mold containing one-half of a polycarbonate (PC) dogbone. The resulting series specimens were notched at the interface and tested in tension. Adhesion of the two materials was reasonably good, as demonstrated by fracture surfaces that showed a mixture of PC and C fiber PEEK fragments. Interfacial fracture energy of the composite was approximately 1.5 kJ/m(2), which is comparable to the cohesive strength of amorphous commodity polymers. Variations in test speed (below the glass transition temperature of the two components, approximately 140 degrees C) had no appreciable affect on stiffness or fracture energy. However, fracture energies decreased slightly as temperature increased.