32 - Digital image correlation: Advancing mechanical property characterization of adhesive joints

Abstract

Digital image correlation (DIC) techniques bring a versatile and robust platform, along with unique capabilities, to experimental methods for measuring full-field deformations across a wide range of applications. Researchers and practitioners in the field are increasingly implementing DIC techniques to enhance their understanding and characterization of adhesively bonded joints. Following a brief overview of the method, this chapter will review some of the recent applications and emerging methods relevant to the adhesion field. Reported studies include constitutive behavior characterization of both bulk and in situ adhesive layers, implementation to reveal stress concentrations in strength test specimens and prototypes, determination of local deformations for correlations with finite element models, and possible extensions to the nondestructive inspection of bonded systems. DIC is also making significant contributions to our understanding of fracture processes and characterization of fracture behavior in bonded joints. The improved toughness of modern adhesives offers added capabilities, reliability, and robustness, but larger strain capabilities and higher fracture energies also complicate their evaluation using traditional linear elastic fracture mechanics approaches. Using DIC, researchers have developed improved methods, adapting testing techniques, data reduction, and model correlation with the evolving performance of tougher adhesive materials. A simple method combining DIC results with cohesive zone models is shown to be a robust method for calibrating fracture properties and traction-separation laws for adhesively bonded joints. This chapter will provide an overview of these DIC applications and how they are advancing our ability to test, characterize, model, and design bonded systems.