Assessing the Applicability of Digital Image Correlation (DIC) Technique in Tensile Testing of Fabric Composites

Report No. ARL-TR-6343
Authors: Brian P. Justusson, David M. Spagnuolo, and Jian H. Yu
Date/Pages: February 2013; 24 pages
Abstract: Performing mechanical characterization of novel structural materials and accounting for the types of failures observed and the heterogeneous nature of fiber-reinforced composites (FRCs) require non-contact strain measurements such as Digital Image Correlation (DIC), a photogrammetric technique that relies on a series of digital images taken during mechanical testing to calculate displacement within a local field. This work assesses the applicability of DIC in determining strains in thick fabric composites by examining two different engineering strain measurement methods available in DIC: (1) the average strain of the full strain field of the tensile specimen and (2) the strain between two gauge points. The results indicate that the difference between the two strain measurement methods is minimal until near the point of failure. However, the full strain fields of the front and back surfaces of the tensile specimen differed significantly during the initial loading. The usage of a single camera DIC system that records only one side of specimen does not accurately capturing bending behavior in the specimen and may inaccurately report the mechanical properties. The DIC technique has to be applied properly in mechanical testing to assure compliance with American Society for Testing and Materials (ASTM) testing methods and other test standards.
Distribution: Approved for public release
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Last Update / Reviewed: February 1, 2013