Characterization of R-curve behavior of translaminar crack growth in cross-ply composite laminates using digital image correlation

• The R-curves of translaminar fracture of composite laminates were measured by DIC.
• Both of the nonlinear least-squares method and conservation integrals were applied.
• The error analysis of least-squares method and conservation integral was conducted.
• The effective crack length was determined from the far-field data.
• Consistency was found between the results of two methods.

This paper presents experimental methods to estimate crack-tip field parameters and characterize R-curve behaviors of translaminar fracture in cross-ply composite laminates using digital image correlation. The investigated crack-tip field parameters include stress intensity factor, energy release rate and effective crack length. The nonlinear least-squares method and conservation integrals are used to determine these parameters from elastic far-field displacements, based on the homogeneous approximation of anisotropic solids for composite laminates. The sources of error of the two parameter-estimation methods are investigated. The results of the two methods show good consistency. Finally, the two-stage rising R-curves are obtained with acceptable accuracy.