Digital image correlation aided method for identification of nonlinear constitutive parameters of IM7/8552 carbon fiber/epoxy composite unidirectional laminate along thickness directionction

A digital image correlation (DIC) aided method combined with finite element model updating (FEMU) technique was proposed to identify the compressive constitutive parameters along the thickness direction for carbon fiber/epoxy (IM7/8552) orthotropic composite unidirectional laminate through short beam shear (SBS) test. The stress and strain distributions on the loading plane along the thickness direction under the loading nose were calculated by 3D finite element model (FEM) with the initial trial parameters, a cost function of the square difference between DIC-measured and FEM-calculated strains was given accordingly and unknown constitutive parameters were determined iteratively through minimization of it. The stress distribution is weakly sensitive to the constitutive parameters since the SBS test configuration is nearly statically determinate. Thus minimization of the cost function can be achieved by the least squared linear regression between FEM-calculated stress and DIC-measured strain. The advantages of the proposed method include that an explicit sensitivity matrix is not required in the iterative procedure, the efficiency of the parameter identification is high, and it is not sensitive to the initial trial parameters.