Ultrastructural Characteristics of Wood Fracture Surfaces

Abstract

This study concentrated on the ultrastructural characteristics of hardwood fracture surfaces, but it included southern yellow pine as a representative iofiwood for comparison.Very small specimens were made.tested for comoression oarallel to the erain.tension ~arallel to the psain, shear in the radial plane and shear in the tangential plane, and were then prepared for scanning electron microscopy.Secondary electron micrographs of the fracture zones were recorded singly or in stereo pairs, and a number are used to illustrate the major findings.Thick-wall cells tend to fail in an intrawall pattern at the SIlS2 interface, while thin-walled cells are more likely to fail with transwall fracture.In tangential shear tests of ring-porous woods, the plane offracture follows the earlywood vessels which are thin-walled and have wide lumens.Large oak-type rays affect the fracture path in all of the test modes.Certain characteristic types of failure can be related to each of the testing modes utilized.