THERMAL-WAVE IMAGING OF PROPAGATING CRACKS IN POLYMERS

Thermal wave imaging techniques, using both an Inframetrics IR740 Came ra and a Santa Barbara Focal Plane InSb array camera, have been used t o measure the temperature distributions around propagating cracks in p olymer materials. Cracks have been initiated under tensile stress with various strain rates, and in several different polymer materials. The time-dependent thermal behavior is then studied. This behavior includ es elastic cooling, followed by heating caused by plastic deformation in the stressed region prior to crack formation, and localized heating as the crack initiates and propagates, followed by diffusive cooling after failure. The fullfield picture provides also information about t he interaction of cracks with pre-existing flaws, and the dynamics of the interaction between two cracks.