CHEMICAL PROCESSING OF TIMBER Treatability The ease with which a timber can be impregnated with liquids, especially wood preservatives, is generally referred to as its treatability. Treatability is related directly to the permeability of timber. The permeability is a function not only of moisture content and temperature, but also of Read more…
MECHANICAL PROCESSING OF TIMBER Solid Timber Sawing and planing: The basic requirement of these processes is quite simply to produce as efficiently as possible timber of the required dimensions having a quality of surface commensurate with the intended use. Such a requirement depends not only on the basic properties of Read more…
Performance of Timber in Fire The performance of materials in fire is an aspect of durability that has always attracted much attention, not so much from the research scientist, but rather from the material user who has to conform with the legislation on safety and who is influenced by the Read more…
FACTORS AFFECTING DURABILITY OF TIMBER Photochemical Degradation On exposure to sunlight the coloration of the heartwood of most timbers – e.g. mahogany, afrormosia and oak – will lighten, though a few timbers will actually darken, e.g. Rhodesian teak. Indoors the action of sunlight will be slow and the process will Read more…
STRENGTH, TOUGHNESS, FAILURE AND FRACTURE MORPHOLOGY There are two fundamentally different approaches to the concept of strength and failure. The first is the classical strength of materials approach, attempting to understand strength and failure of timber in terms of the strength and arrangement of the molecules, the fibrils, and the Read more…
FACTORS AFFECTING STRENGTH IN TIMBER Many of the variables influencing modulus of elasticity also influence the various strength properties of timber. Once again, these can be regarded as being either material dependent or manifestations of the environment. Anisotropy and Grain Angle The marked difference between the longitudinal and transverse planes Read more…
Failure & Strength in Timber While it is easy to appreciate the concept of deformation primarily because it is something that can be observed, it is much more difficult to define in simple terms what is meant by the strength of a material. Perhaps one of the simpler definitions of Read more…
Viscoelastic Deformation in Timber Timber is neither truly elastic in its behaviour nor truly viscous, but rather a combination of both states; such behaviour is usually described as viscoelastic and, in addition to timber, materials such as concrete, bitumen and the thermoplastics are also viscoelastic in their response to stress. Read more…
Creep in Timber Creep Parameters It is possible to quantify creep by a number of time dependent parameters, of which the two most common are creep compliance (known also as specific creep) and relative creep (known also as the creep coefficient); both parameters are a function of temperature. Creep compliance Read more…
Deformation in Timber Under Load This article is concerned with the type and magnitude of the deformation that results from the application of external load. As in the case of both concrete and polymers, the load–deformation relationship in timber is exceedingly complex, resulting from the facts that: timber does not Read more…