Semi-experimental investigation of bridging tractions in delamination

Abstract

Bridging by intact fibers is well recognized as an important toughening mechanism that accompanies delamination propagation in fibrous laminates. However, direct measurement of the bridging tractions is a challenging task. In this work, an iterative methodology based on internal strain measurements and parametric finite element modeling is employed to identify the contribution of fiber bridging to delamination resistance of unidirectional carbon fiber/epoxy laminates. Double cantilever beam specimens with integrated arrays of wavelength-multiplexed fiber Bragg gratings (FBG) are subjected to mode I loading. Non-uniform strain distribution in the vicinity of the interlaminar crack plane is locally monitored by means of the several embedded FBG sensors of 1 mm gauge length. Employing an inverse identification procedure, the measured strain data are used to determine the bridging tractions associated with delimitation growth. It is shown that such an iterative procedure can be effectively applied for characterization of the energy release rate due to the fiber bridging in specimens of different thicknesses. © The Society for Experimental Mechanics, Inc. 2014.