Key mechanical properties include the modulus of elasticity (E), which measures stiffness, and Poisson's ratio, which describes lateral deformation under axial stress. The modulus of rigidity (G) defines resistance to shear stress. Strength properties include modulus of rupture (MOR) in bending, compressive and tensile strengths, and shear strength parallel to the grain. Wood also exhibits impact bending strength, hardness, and fracture toughness, which define its ability to resist impact, indentation, and crack propagation.

Growth features like knots, slope of grain, and reaction wood significantly impact strength. Knots weaken wood by disrupting fiber continuity, while juvenile wood has lower strength due to a high fibril angle. Compression wood in softwoods and tension wood in hardwoods have higher density but undesirable shrinkage properties.

Wood's mechanical performance is affected by moisture content, temperature, and prolonged loading. As moisture decreases, most mechanical properties increase, but excessive drying can cause brittleness. Prolonged load exposure leads to creep and potential failure over time. Wood's resistance to decay, insect damage, and fungal attack depends on its species and treatment methods.

Wood treatments, including preservatives and fire-retardants, can impact strength. While oil-based treatments have minimal effects, waterborne preservatives can reduce strength, particularly at high temperatures. Aging and exposure to chemicals may also alter mechanical properties.

Understanding these factors helps in designing durable wood structures, ensuring wood's continued viability as a sustainable engineering material. This low-tech course includes a multiple-choice quiz at the end and is intended to provide 4 hours of professional development. 

 Wood's orthotropic nature and its mechanical properties in three perpendicular directions. Key mechanical properties, including elasticity, rupture, shear, and compression strength. 

 Poisson's ratios and their role in wood deformation under axial loading. 

 Identification of different strength properties, such as bending, tensile, and impact resistance. 

 Discussion of how knots weaken wood, affecting tensile and bending strength. 

 The impact of grain slope on strength and stress concentration. 

 Juvenile wood properties and why it is weaker than mature wood. 

 Normal and reaction wood, including compression and tension wood effects. 

 The role of specific gravity in wood density variations and strength. 

 The effect of moisture content on strength and fiber saturation. 

 The impacts of temperature, including short- and long-term effects on elasticity. 

 Creep in wood, and how prolonged loads cause deformation. 

 Fatigue in wood, and how cyclic stress weakens it. Heat exposure effects, leading to permanent strength loss. 

 The potential impact of chemical treatments, such as preservatives and fire retardants. 

 Decay fungi degradation vs. mold and stain fungi. 

 The effects of nuclear radiation on wood's mechanical properties.

 Testing standards for evaluating wood strength, such as ASTM D 143. 

 Environmental influences, including humidity, temperature, and exposure. 

 The application of wood mechanics principles to structural and engineering applications.