Investigating Factors Influencing Rolling Shear Performance of Australian CLT Feedstock

This paper presents an investigation on the influence of various factors on rolling shear (RS) properties of timber feedstock for cross laminated timber (CLT) available from Australian plantation forest resources. Comparison of RS properties between three softwood species namely southern pine, radiata pine and hoop pine are presented. Furthermore, the effect of modulus of elasticity (MOE), equilibrium moisture content (EMC), aspect ratio, knots and projection length on rolling shear behaviour were investigated. Mean RS modulus for radiata pine, southern pine and hoop pine samples were 74.7 MPa, 87.1 MPa and 99.7 MPa, whilst the RS strength of those species were 2.6 MPa, 3.1 MPa and 3.7 MPa, respectively. Radiata pine samples exhibited the lowest values for RS modulus and strength, almost 30% less than those of hoop pine samples. The study confirmed that the density and MOE had a very weak correlation with RS properties for all pine species. There was an obvious decrease in RS modulus (by 18%) when the woods' conditioned EMC changed from 8% to 12%. A further 33% decrease was observed when the woods' conditioned EMC increased from 12% to 16%. However, the percentage increase in RS strength was found to be 23% higher in wood with 12% conditioned EMC while compared against wood conditioned to 16% EMC. RS strength improved with increased aspect ratio; however, RS modulus remained almost unaffected. Moreover, the projection length that resulted in the load passing through the centroid of the specimen resulted in lower RS modulus values, but the presence of knots improved both RS strength and modulus for all three tested species.