Measurement of the Mode I Critical Stress Intensity Factor of Solid Wood and Medium-Density Fiberboard by Four-Point Single-Edge-Notched Bending (4SENB) Test

Abstract

Mode I critical stress intensity factor K_Ic obtained by four-point single-edge-notched bending (4SENB) tests of wood and medium-density fiberboard (MDF) was experimentally and numerically analyzed. To determine the critical load for crack propagation, the relationship between the load and loading-line deflection (LLD) and that between the load and crack opening displacement (COD) were measured, and the results obtained were compared with each other. Additionally, a double cantilever beam (DCB) test was conducted and the results were compared with those of 4SENB tests. Similar to the results obtained in several previous studies, the value of K_Ic was obtained by introducing an additional crack length into appropriate equations as the crack geometry factor used for analyzing the 4SENB test. Additionally, the load-COD relationship was more sensitive in detecting the crack propagation than the load-LLD relationship, so the measurement of COD is recommended for determining the K_Ic value in the 4SENB test accurately.