Study of deformation and fracture of polymers and metals using infrared imaging methods.

摘要

Thermal image methods for studying fracture behaviors of polymer and metal materials are presented in this thesis. Using IR camera with high speed and high spatial resolution, the spatial and temporal distribution of temperature on the surface of the sample under tensile load are obtained, along with the synchronized load-displacement data. Since the deformation of the material is always associated with thermal events, the temperature distribution reflects the stress and strain level and provides important information of the fracture, like crack tip position, yielding zone size, and the integral of the temperature increase can be used to estimate energy consumption during fracture. The transmitted and emitted IR image method is used in studying rubber modified polystyrene samples. The difference between the transmitted IR signal and emitted IR signal reveals the IR absorption inside the sample. The result shows the sudden change of the optical property, accompanied with the start of heating, at the low yielding point of this material, which results from crazing mechanism. This result is consistent with AFM and optical microscopic study. It demos the potential use in detecting failure initiation of some polymer materials.