A study to quantify the tension perpendicular to grain (or extrusion direction) strength of dimensional lumber, laminated veneer lumber (LVL), and wood plastic composite (WPC) structural members has been completed. Wood, LVL and WPCs display orthotropic properties where decreased properties are noted perpendicular to the primary direction of the member (member axis or extrusion direction). The study was undertaken after significant evidence that tension perpendicular failures were controlling the failure mechanisms for diaphragms with framing members using LVL related products and shear walls using WPC for sill plates. The tension perpendicular to grain study followed the ASTM D143 test standards for fabricating the test specimens and conducting the tests. The results indicate that LVL does have lower tension perpendicular to grain strength than solid wood and that WPC has higher strength than wood, but is adversely affected when employing certain die technologies for manufacture.
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