Monitoring creep-rupture in oriented strandboard using acoustic emission: Effects of moisture content

Abstract

Abstract Creep-rupture studies of large specimens of commercial oriented strandboard (OSB) were conducted using a fourpoint flexural test in combination with an acoustic emission (AE) monitoring system. Four equilibrium moisture content (EMC) conditioning and testing regimens were used: ambient room conditions, constantly moderate EMC (12/12), dynamic rising EMC (12/24), and constant high EMC (24/24). Compared with deflection, the cumulative event AE parameter was found to be more sensitive and representative to detect cumulative damage to final failure. Under 80% ultimate stress, the 24/24 specimens had the highest creep rate (1.43 mm h−1) as compared with 0.27 and 0.04 mm h−1 for 12/24 and 12/12 specimens, respectively. However, for the 12/24 specimens, a step-like deflection occurred, accelerating the rupture process and attaining the greatest creep factor of 2.28—a recommended safety factor for prolonged exposure to humid service conditions. The total recovered deflection under ambient conditions was 85% recoverable elastic, 5% recoverable viscoelastic, and 10% permanent irreversible creep. Correspondingly, the total recovered stiffness was 70% recoverable elastic, 10% recoverable viscoelastic, and 20% permanent irreversible creep. The observed creep-rupture limit of the OSB was 24 days to failure.