Fracture behaviour of Green Wood (Pinus Sylvestris L.) : a composite materials approach

Sammanfattning: The fracture behaviour of green wood has been investigated using a composite materials approach. Through fracture experiments on miniature specimens, it was found that drying of wood leads to damage not only on the macro-level but also at the scale of the cell wall. Modelling of the hygroscopic stresses during drying revealed that this is due to the laminated and anisotropic nature of the cell wall. Crack growth experiments on radial cracks demonstrated the importance of the scale of annual rings to stick-slip behaviour during crack growth. The strain field at the crack was determined by optical methods, calculations using the finite element method complemented the experimental data. The importance of the stiffness difference between earlywood and latewood was apparent.