The total timber stock of Germany´s forests is fast growing. From 1987 to 2002 the hardwood stock increased more than three times as much as the softwood stock. The lack of knowledge concerning test standards, product standards and sorting criteria makes it difficult to expand the processing and marketing of hardwoods into the field of construction usage. Strength and stiffness data derived from little, error-free specimens do mostly exist, but in order to be able to insert hardwoods into building applications, data derived from real size specimens is needed. Subsequently the results of these two different specimen categories need to be correlated and the so-called “size effect” needs to be quantified and qualified.
This paper aims to analyze the size effect of error-free compression, bending and tensile specimens for the six European hardwoods maple (Acer spp.), birch (Betula pendula), beech (Fagus sylvatica), ash (Fraxinus excelsior), oak (Quercus spp.) and lime (Tilia spp.). They are tested exclusively parallel to grain.
Regarding the compression strength for maple, birch and ash the specimen’s dimensions did not influence the compression strength. For beech, oak and lime it was observed that compression strength increased as the specimen’s volume was increased. The bending strength of all species decreased as the specimen’s dimensions were increased. Concerning the tensile strength, a clear statement on whether specimen’s dimensions do or do not influence the tensile strength is not possible. Further research with adjusted specimen sizes and shapes is needed.
Regarding the compression and bending MOE in most cases the specimen’s dimensions did not influence the MOE values. In tensile testing MOE values differed significantly for the different specimen sizes.
Keywords: bending test, compression test, hardwood, size effect, tensile test
Authors
Schlotzhauer P.
Department of Wood Biology and Wood Products, Georg-August-University of Göttingen, Göttingen
Nelis P. A.
Department of Wood Biology and Wood Products, Georg-August-University of Göttingen, Göttingen
Militz H.
Department of Wood Biology and Wood Products, Georg-August-University of Göttingen, Göttingen
Bollmus S.
Department of Wood Biology and Wood Products, Georg-August-University of Göttingen, Göttingen
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