Experimental Study of Furfurylation Effect on Fracture of Beech Wood under Mixed Mode

Fracture of mixed mode I/II in beech wood and its wood polymers has been investigated experimentally in this study. Hence, two crack systems of TL and RL were selected in which the crack planes extend along the wood fibers. This investigation has demonstrated that onset of mixed mode cracking can be predicted with a very simple fracture criterion in these crack systems. Results indicated that fracture critical loading is affected by furfurylation and also load-displacement curves of specimens were changed. Variations in fracture toughness values of mixed mode I/II can be occurred following variations of fracture critical forces. In the both crack systems, KIC/KIIC distribution trend is changed by furfurylation that indicates changing of material nature by furfurylation. Results of scanning electron microscopy (SEM) analyses indicated that micro cracks occurrence in wood polymer structure may be one of the factors caused to change in fracture toughness; these changes occur simultaneously with material nature modification followed by increasing of shear strength parallel to the grain due to polymerization.