The fracture mechanic of wood and wood composites in the process of mechanical machining

Subject description

Basic mechanical properties of materials such as modules of elastic, shear modules, Poisson's relationships, and normal and shear strength in basic directions today are not sufficiently sufficient to evaluate the mechanical properties of materials in the process of mechanical machining technologies as well as in wood construction. One of the modern mechanical properties of materials that persistently develop in recent decades is definitely a fracture mechanics.

Without it, it can not be sufficiently successful to analyze the limit forces in wood structures as well as in the process of cutting various materials. It is also necessary to take into account the combination of all the above-mentioned stress conditions in the fracture processes.


The contents of the course include:

The basics of fracture mechanics of isotropic and orthotropic materials, such as wood and wood composites. Basic modes of fracture mechanics: I, II and III (tensile, shear). Combination of normal and shear modes. Distribution of stress in front of the crack tip. The importance of the critical intensity of stress and fracture energy in the process of creating new surfaces. The impact of the critical stress intensity factors on the size of the destructive load of the material. The effect of the crack size on the destructive load of the material. Differences between fragile and ductile materials. Stable and unstable progression of cracks. Crack initiation. Methods of determining the critical strss intensity factors and strain energy rates. The influence of the shape and different sizes of samples to determine the fracture properties of the material.

The influence of a combination of various stress conditions on the collapse of the material. Different failure criteria: TSAI-Wu, Puck, TSAI-Hill …

The subject is taught in programs

Objectives and competences


Obtain in-depth knowledge of modern mechanical properties of materials such as a fracture mechanics in various processes and wood construction. Acquire knowledge to determine the fracture properties of materials and use them accordingly in various situations.


The student independently evaluates the importance and size of the fracture properties of materials in various situations, thus taking appropriate action or determines failure loads in various cases.

Teaching and learning methods

Lectures (10 h)
Seminar (20 h)
Laboratory work (10 h)
Others (5 h)

Expected study results

Knowledge and understanding:

Knowing the fractures of different materials according to specific loads. Understanding cracking in the process of material fracture in various situations.

Basic sources and literature

Smith, Ian / Landis, Eric / Gong, Meng. 2003. Fracture and Fatigue in Wood, Wiley & Sons Ltd

Knott, J. F., 1976. Fundamentals of fracture mechanics – Butterworths,; London

João, P. D. 2008. Machining. Fundamentals and Recent Advances. Springer-Verlag London.

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