Ultrasonic Fractography Studies on Discontinuous Fracture Propagation in Polymers

Ultrasonic fractography studies were performed on glassy polymers, PMMA and epoxy. Transient fracture velocity change during highly discontinuous propagation in DCB type PMMA specimens has been measured precisely. It has been shown that fracture abruptly slows down with a speed on the order of 10 0 m/s. Measurements in pre-cracked epoxy resins, araldite-B and -D, revealed that the former had two kinds of initial fast fracture velocities just after the onset of instability, while the latter exhibited behavior similar to pre-cracked PMMA tensile specimens.