Fractography of Amorphous Polymers - A Comparison of Tensile, Impact, and Environmental Stress Cracking Fracture Surfaces

The need for more weight-, cost- and energy-efficient materials in modern engineered products has resulted in a strong shift toward the use of load-bearing polymeric materials across many industries. In comparison to more conventional structural materials such as metals, the microstructure and chemical compositions of polymeric materials are unique. As a result, the bulk physical property limits and potential failure modes area also unique. Deciphering the differences between a tensile, impact, or an environmentally-stressed fracture surface requires a nuanced process that is distinct from classical fractography used for metals, glasses, and ceramics. This work presents an effort to document and describe fracture surfaces for three common commercially available amorphous polymers (polycarbonate, polymethylmethacrylate and acrylonitrile butadiene styrene) each subjected to tension, impact, or environmental stress cracking (ESC). We present mechanical properties as well as microscopic characterization at low and high magnification to distinguish between slow tensile loading, fast impact loading, and environmentally (chemically) assisted creep failure mechanisms. Analysis of select fracture surfaces using chemical characterization methods was also performed to evaluate the utility of such tools to diagnose ESC failure. The fractographic atlas presented will serve to assist others in identifying topographical fracture surface features and crack growth mechanisms of failed polymer components, and more accurately distinguish between pure mechanical-induced failure and ESC-generated fracture, where possible.