Characterization of fatigue crack growth in unidirectional carbon fiber epoxy composites using digital image correlation

This work studies fatigue fracture behavior of carbon fiber laminated composites by measuring deformation fields directly from the surface of the material using Digital Image Correlation (DIC). Energy release rate of laminated composites was determined from DIC measurements using Linear Elastic Fracture Mechanics (LEFM) theory under different mixed mode loading. Crack tip location was more accurately identified using the DIC and it was found that the strain energy release rate strongly depends on accurate identification of crack tip. The energy release rate determined from direct deformation measurement was compared with that obtained from global load displacement response of the materials as per ASTM standard. Evolution of energy release rate under cyclic loading has been quantified. Attempt has been made to identify the micro-mechanisms in the material under fatigue load through high magnification imaging and deformation analysis. The present work is an attempt to utilize the full field measurement of deformation around the crack tip to characterize fatigue fracture behavior.