Post-impact Non-destructive Evaluation of Homogeneous Sugarcane Bagasse Particleboards

摘要

With a view to gaining an in-depth assessment of the response of particleboards to different in service loading conditions, samples (50×50×15 mm) of high-density homogeneous particleboards of sugarcane bagasse and polyurethane resin based on castor oil were manufactured and subjected to low velocity impacts. An instrumented drop weight impact tower was used to impact the specimens at four different energy levels, namely 5, 10, 20 and 30 J. The prediction of the damage modes was assessed using Comsol Multiphysics computer program. In particular, the random distribution of the fibres and their lengths were reproduced through a robust model. An average value of the residual dent depth, as well as the 3D reconstruction of each impacted surface were performed. The experimentally obtained depths of the mechanical imprints due to the impactor were compared with the ones numerically simulated. The postimpact damage was evaluated by a simultaneous system of image acquisitions coming from two different sensors. Specifically, thermograms were recorded during the heating and cooling phases, while the specklegrams were gathered only during the cooling phase. On one hand, the specklegrams were processed via a new software package named Ncorr v. 1.2, which is an open-source subset-based 2D digital image correlation (DIC) package that combines modern DIC algorithms proposed in the literature with additional enhancements. On the other hand, the thermographic results linked to a square pulse were compared with those coming from the laser line thermography (LLT) technique that heats a line-region on the surface of the sample instead of a spot. The numerical results demonstrate how the estimation of the dent depth is very close to the measured one. By comparing the typical residual indentation profile with the laser line scan thermography result, it is possible to find a reasonable correlation between a satellite defect and a slight concavity at the border of the impacted area.