Evaluation of structural change and local strain distribution in polymers comparatively imaged by FFSA and OCT techniques

Mechanical material testing combined with optical coherence tomography (OCT) allows for the first time the immediate detection of inner structural changes along with a qualitative observation of the local strain distribution in surface near bulk regions of semitransparent and translucent specimens. In addition to a 3D full field strain analysis (FFSA) system based on digital image correlation (DIC), a customized spectral domain OCT system operating at 1550 nm was applied for investigation. Exemplified by tensile testing of elastomer particle filled polypropylene specimens, local dissimilarity evaluation of the OCT images was performed. The results show the high potential of OCT to provide complementary information to DIC-based FFSA, like to identify processes influencing the remaining life of advanced commodity plastics such as the start and progress of yielding, identification of the yielding point, localization of the necking front and the development of small scale voids as in the case of matrix crazing