UC Davis

Non-destructive testing methods often provide a key understanding of damage when examining carbon fiber-reinforced polymers (CFRP) without compromising their structural integrity. Yet the limitations of various accurate nondestructive testing (NDT) methods decrease the range of application within the commercial aerospace world due to the scale and complexity of parts post assembly. The study of this thesis investigated impact tests performed on T300 carbon fiber-reinforced polymer samples to understand if analysis by 2D digital image correlation (DIC) can be used to identify barely visible impact damage (BVID). The intent is that this process could allow monitoring of impact damage on an aircraft if baseline pre-impact images are available for those components. T300/epoxy plate samples were created through VARTM (Vacuum Assisted Resin Transfer Modeling), impacted following ASTM 7136 guidelines, and tested for residual compressive strength according to ASTM 7137 guidelines, to showcase the extent of damage. Strain of the pixels between images was calculated through DIC (Digital Image Correlation) from Correlated Solutions VIC 2D commercial software. A Lagrange tensor type was chosen for strain computation with a normalized squared differences criteria for correlation. The results provide a range of impact imagery via DIC on frontal (impacted) and posterior sides of the samples. By cross-referencing other NDT methods applied to impacted T300/epoxy at the same or similar energy levels and nearly identical manufacturing techniques, 2D DIC shows promising evidence that it could provide evaluation of damage from BVID on CFRPs.