THE MORPHOLOGY OF WOOD IN RELATION TO 

 BRASHNESS 



(Contribution from the Department of Wood Technology, New York State College of 

 Forestry, Syracuse University) 



By C. C. Forsaith 



Assistant Professor of Wood Technology, College of Forestry, 

 Syracuse University 



Before the era of steam and other mechanical engines, the question 

 of defects in wood was not seriously considered both on account of an 

 abundant supply from which only the best need be selected and also 

 because the strains to which is was subjected in horse-drawn vehicles 

 were relatively slight in comparison with those encountered in modern 

 practice. Furthermore the size and weight of structural members in 

 those days did not prohibit construction allowing a high factor of 

 safety. The introduction of the gas engine into industry, however, 

 changed this situation, and especially in connection with aircraft pro- 

 duction, at once raised the problem of brashness and other imperfec- 

 tions to a plane of vital importance. Not only did the greater stresses 

 produced by a powerful motor subject the assembled parts to excep- 

 tional strains, but also the need for lightness made necessary a reduc- 

 tion in size and a corresponding lessening of the factor of safety out of 

 all proportion to that formerly considered to be a minimum. Such a 

 development made it essential to employ only those timbers which were 

 free from defects. 



Wood is heir to many imperfections, but none is more subtle or more 

 treacherous in its liability to failure than brashness, and since this 

 paper deals particularly with the underlying causes for such a defect 

 a few words of definition will not be out of place. 



Brashness, a synonym for brittleness, is that property inherent in 

 wood which causes timber under strain to break suddenly, with a sharp 

 report, and to leave on rupture smooth, unsplintered surfaces. A 

 fracture of this type is shown in figure 9 which represents the broken 

 ends of a stick of brash tulip poplar, Liriodendron tidipifera. A non- 

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