습도반복처리조건하에서의 목질재료의 내구성능평가 ( I )

Performance of Wood Based Materials Under Cyclic Humidity Conditions ( I ): Fracture Toughness of Wood Based Materials

Bending test were carried out on nominal 15mm thick commercial Plywood, MDF and Particleboard under alternating humidity conditions (40%-80%) with constant temperature of 20 C. Specimens were prepared with a set of notched and unnotched conditions and tested using midspan loading. By the test results, retention of flexural strength, MOE and fracture toughness were calculated. Typical load-deflection curves were different in3 types of tested specimens respectively, and especially linear to fracture in PB. Time to fracture in MDF was longer than Plywood and PB. The retension of flexural strength of un notched specimens varied in each cycle, and MOE was decreased considerably in PB and MDF panels. Stress concentratjon factor and critical stress intensity factor were decreased as the cycles were repeated, especially after 3~4th cycle, The effect of alternating humidity conditions on panel performance was higher in PB panels than in plywood and MDF panels. This study will offer the convenience of comparing the behavior of wood-based panels under cyclic humidity conditions by means of fracture toughness and retention of performance.