Effects of embedded cylindrical sensor tubes on the Mode-II fracture behavior of adhesively bonded composite laminates

Abstract

Influence of embedding a cylindrical sensor tube on mode-II interlaminar fracture behavior in adhesively bonded composite laminates has been investigated experimentally and numerically. Three laminates with varying sensor locations along the thickness and one laminate without a sensor were fabricated. Presence of sensor in the composite caused fiber and adhesive misalignment which was quantified using a microscope. Experiments were carried out using four-point bending test setup following a load-unload-reload approach. Effect of sensor on fracture behavior was not observed in any case. However, as crack approached the sensor, an abrupt crack growth was noticed. This was attributed to the presence of residual stresses in the specimens formed during curing. In order to study these effects and get a better understanding of the influence of a sensor, finite element analysis was performed. Two-dimensional, plane strain models using Virtual Crack Closure Technique were developed. An additional study was performed to observe the effects of a vasculature in the model instead of sensor. While compressive residual stresses were noticed around the sensor, tensile stresses were noticed in the model with vasculature. Effect of sensor on interlaminar fracture behavior was not noticed in numerical simulations. Resistance curves and force-displacement curves of the numerical models were compared with experimental results.