Orthotropic strength and elasticity of hardwoods in relation to composite manufacture. Part II. Orthotropy of compression strength and elasticity

The effect of grain and annual ring orientation on the compression strength (a,,) and modulus of elasticity (E.) of small clear specimens of hardwood species was investigated. The experimental and analytical works explored the orthotropic nature of three North American (quaking aspen, red oak, and yellow-poplar) and two European (true poplar and turkey oak) hardwood species under uniaxial compression. Apparent compression strength and modulus of elasticity were measured at 15degrees grain and ring angle increments. The three-dimensional Hankinson's formula and another model, based on orthotropic tensor theory, were evaluated for predicting the anatomical direction-dependent properties of the species. Statistical analyses revealed that both models approximate the compression strength and elastic properties reasonably well. Either the analytical or the experimental results can be used for further modeling the orthotropic properties of structural composites.