Comparative studies on the torsion behavior of California foothill pine and red pine

Abstract

Pine wood as natural composite has been extensively used in building construction, manufacturing furniture, and making musical instruments. California foothill pine or gray pine (Pinus sabiniana) is used as basic building materials for box crates and railway ties. It is also used for musical instruments (drums) making. Red pine (Pinus resinosa) is strong and durable for making furniture and flooring. It is suitable for outdoor applications such as fencing and framing, railroad ties, and cabin logs. Red pine wood also finds applications in musical instruments, especially for guitar bodies, offering warm and resonant tones. Mechanical testing is indispensable for design and performance enhancement of pine wood structures and components. Since the bonding strength and wear resistance of wood are related to shear deformation behavior, torsion test is considered as an effective method for evaluating the performance of pine wood. In this work, the strength and rigidity of both California foothill pine (gray pine) and red pine were evaluated under pure shear through torsion test. It has been found that the average shear strength of the gray pine is 7.12 MPa. The red pine showed higher average shear strength of 14.67 MPa. The modulus of rigidity of the gray pine is about 2.59 ± 0.46 GPa; while the red pine has the modulus of rigidity as high as 3.47 ± 0.62 GPa. Statistical analysis of the shear strength data reveals the Weibull moduli (m) of gray pine and red pine are 2.44 and 3.74, respectively. The characteristic shear strength (with a failure probability of 63.2%) of the gray pine is 8.04 MPa. The value of characteristic shear strength for red pine is 16.15 MPa. The statistical analysis on both pines indicates that the red pine is over one time stronger than the foothill (gray) pine under torsional loading.