Application of Digital Image Correlation in Hygrothermal-Mechanical Testing of Fiber Reinforced Composites

Abstract

The Office of Naval Research High-Fidelity Building Block and Validation Protocols for NextGen Composite Methods project aims to develop validation protocols for NextGen structural analysis methods. For this purpose, more experimental validation data is needed in matrix dominated failure events and adhesive bonded joints under the effects of temperature and moisture. Matrix dominated events test articles and adhesive bonded joints were tested at elevated temperature wet (ETW, 180F), room temperature ambient (RTA, 70F), and cold temperature dry (CTD, -65F) conditions. Tests at cold and elevated temperatures are enabled by a custom oven that is designed for hot and cold mechanical tests with noncontact optical tracking of displacements and strains with minimal interference for the purpose of Digital Image Correlation (DIC). This article will discuss the use of DIC at hygrothermal mechanical loading and methods to mitigate interference in the optical measurements. Noise is introduced to the optical signals due to circulating air, moisture, and refraction. This is illustrated in applications in tensile, shear, and fracture specimens.