On the fracture morphology in wood

Summary Failure forms caused by axial ultimate compression stress in three softwood and nine hardwood species and in model specimens made of wood, paper and plastics are described. Three categories of failure forms are distinguished: 1. Wood characteristic failure forms are connected with the general anisotropic structure of the wood. 2. Failure forms specific to the species are modifications of the first category arising from predominant anatomical structures. 3. Modifications of the failure forms are also induced experimentally. The interdependence among the anatomical structure, strength characteristics and failure forms of the wood specimens are examined by statistical methods. The structure cipher introduced in this paper, as a numerical characteristic of the anatomical features of the wood species, is seen to be the most important influencing factor as regards the intensity and pattern of the fracture, followed in second and third place by the geometry of the specimen and its specific gravity. Specimen volume and other factors are shown to have only a marginal influence on the fracture morphology.The strength tests were carried out as part of a diploma thesis by K. Buchmüller. Also the assistance of E. Risi in measuring and evaluating is gratefully acknowledged