USING DIGITAL IMAGE CORRELATION TO ACQUIRE FULL-FIELD DISPLACEMENTS AND STRAINS IN CARBON FIBER TENSILE TOW EXPERIMENTS AND MODIFIED IOSIPESCU SHEAR SPECIMENS

摘要

Strain measurement of carbon fiber tensile tow experiments is a challenge due to the inherent fragility of the cured tows.Inadvertent damage can occur to the samples if bonded strain gages or clip-on extensometers are used.In general,the cured carbon fiber tows are brittle and susceptible to failure due to invariable mishandling during the application of the contact strain measuring devices.The premature failure of the tows will invalidate the experimental measurements.Digital image correlation (DIC) offers a non-contact,optical technique for full field strain measurement and provides strains with an accuracy of 0.01%.Furthermore,sample preparation of the tows for DIC only requires an application of a speckle pattern with spray paint in which insignificant damage is done to the composite.This technique was further applied to a modified Iosipescu specimen still conforming to ASTM D5379 test procedures.The DIC results are compared to the data from a strain gage.The authors will discuss the experimental procedure and results.