Evaluation of tensile fracture in Aspen using fractographic and theoretical methods

Abstract

Based on the linear elastic fracture mechanics (LEFM) concept, apparent mode I fracture toughness K(cLR was calculated for unnotched aspen (Populus tremuloides Michx.) specimen (5 in. x 0.188 in.x 0.094 in. dimension) tested in tension parallel to grain. The purpose was to relate wood fracture toughness to average ray spacing. Observations along the longitudinal-radial plane of fracture showed the ray/fiber interface as a notable zone of crack propagation. Step-like progression of fracture lines occurred from one ray to another thus leading to an hypothesis that the average ray spacing could reasonably estimate the critical flaw dimension. Using this model, the calculated k(cLR was close to available published data. In additional experiments, it was revealed that k(cLR is sensitive to decay weight losses. Within 2% to 16% weight loss examined, loss of k., LR was found to be more pronounced with a brown rot fungus when compared to white rot fungi.