New optical methods for measuring laminate stiffness

Finite Element Model Updating Method (FEMU) Virtual Fields Method (VFM) 

Constitutive Equation Gap Method (CEGM) Equilibrium Gap Method (EGM) 

45 Photo-mechanical setup of the digital image correlation. 

46 Schematic representation of the principle of digital image correlation. 

Several mathematical correlation criteria have been proposed for estimation of the displacement fields in the subset matching process. It has been shown that the zero-normalized sum of squared differences (ZNSSD) is a robust algorithm, since it takes into account offset and linear scale variations of light intensity [48]  

---