Energy density and fracture parameters of coated Scots pine

Abstract

An attempt was made to investigate the Michalski’s proven fluctuation theory through the use of the fracture characteristic and the energy density – dynamic surface value – of Scots pine coated with Renaissance wax, paraloid, and tar. The slices were acclimatized in a climate chamber with an abrupt drop of relative humidity from 80% to 30% while being monitored by acoustic emission. During this period, macro-cracks were formed in the slices coated with the paraloid and tar while those coated with Renaissance wax were remained undamaged. Moreover, fracture tests along with the Finite Element Analysis (FEA) were utilized to calculate the critical values of the stress intensity factor. Furthermore, the alternative correlation, accounting for the effect of different specimens’ length, introduced into the ASTM E833 standard resulting in agreeable values of fracture toughness as compared with the experimental data. Finally, the relation between the crack propagation and the fracture toughness with the ductile (load increase) and the brittle (load decrease) portions of the dynamic surface value (DSV) was investigated. It was observed that the impact of the latter portion in the crack propagation of the undamaged slices was more dominant, while the portion contributed almost the same in crack propagation of the damaged slices.