Mixed glued laminated timber of poplar and Eucalyptus grandis clones G. Castro, F. Paganini Abstract The authors investigated the properties of small- sized joint-free laminated beams (80 mm in width, 115 mm in height and 2 m in length) composed of 7 mechanically graded laminations of poplar (Populus x euramericana, ‘Neva’ clone) and eucalyptus (Eucalyptus grandis, ‘7’, ‘329’, ‘330’ and ‘358’ clones) in different combinations. Tests were carried out in order to determine their modulus of elasticity, bending strength and shear modulus; the bonding reliability was also evaluated by means of delamination and shear tests in the glue lines. The beams composed using the ‘330’ eucalyptus clone, by its own or in combination with poplar, showed outstand- ing mechanical performance and the best structural effi- ciency. In addition the bonding quality, also at the interface between the two species, proved to be excellent. The results, separately for each clone of E. grandis, in terms of absolute values and structural efficiency, are shown and discussed. Schichtverklebtes Holz mit einer Mischung von Pappel und Eucalyptus grandis Klonen Zusammenfassung Die Autoren untersuchten die Eigenschaften von kleinen verbindungsfreien Brett- schichttra ¨gern (von 80 mm Breite, 115 mm in Ho ¨he and 2 m Ho ¨he) zusammengesetzt aus 7 mechanisch sortierten Brettschichtho ¨lzern von Pappel (Populus x euramericana, ‘Neva’ clone) und Eucalyptus (Eucalyptus grandis, ‘7’, ‘329’, ‘330’ und ‘358’ Klonen) in unterschiedlichen Kom- binationen. Tests wurden durchgefu ¨hrt, um ihr Elasti- zita ¨tsmodul, ihre Biegefestigkeit und Scherfestigkeit zu bestimmen; die Haftverla ¨ßlichkeit wurde ebenfalls ab- gescha ¨tzt durch Delaminierung und Schertests in den Klebefugen. Die zusammengestellten Balken, bei denen man den 330 Eukalyptusklon verwendete, entweder allein oder in Kombination mit Pappel, zeigten herausragende mechanische Qualita ¨t und die beste strukturelle Leis- tungsfa ¨higkeit. Zusa ¨tzlich erwies sich die Bindefestigkeit, auch an den Grenzfla ¨chen zwischen den beiden Arten als exzellent. Es werden die Ergebnisse separat fu ¨r jeden Klon von E. grandis, als absolute Werte und als strukturelle Leistungsfa ¨higkeit dargestellt und diskutiert. 1 Introduction Laminated timber is a material of a great aesthetic value, with various applications in the field of building compo- nents, such as doors and windows, and in the field of timber structures of big and small spans. At present almost all the timber used in Italy in the production of glued laminated elements comes from abroad also due to the forestry policy in Italy, which often considers the pro- duction role of wood and its economic exploitation as marginal, compared to land hydrogeological protection and landscape recreational functions. The possible use for structural purposes of two fast growing species could stimulate the establishment of specialized non-forest plantations in Italy as well. At the moment the use of laminated timber obtained from a combination of different wood species is quite widespread, but with different end uses rather than structural ones. The technological development of laminated timber provokes continuous evolution; industries, but above all researchers, are now starting to consider the possibility of using a wider range of wood species. Particular attention has been paid to eucalyptus, which shows interesting mechanical properties, and to poplar, which, due to short cultivation cycles (10–12 years), is at national level, for the time being, the only renewable source of wood raw material manageable in the medium time. The possible uses of the latter for structural purposes have been investigated in previous research studies (Cas- tro, Paganini 1993; Castro, Paganini 1997; Pedrotti et al. 1997) carried out on small-sized laminated beams as well as on structural sized beams which have shown a very favourable shear behaviour in terms of strength and rigidity, hence suggesting a convenient use in short span beams and, close to the neutral axis area, in mixed species glued laminated beams. Regarding the E. grandis, in the 1930s, Pavari success- fully introduced this species in Italy, in an area of the National Park of Circeo: these trees are still alive and have reached a remarkable size. Subsequent introductions by the Agricultural and Forestry Experimentation Center of Holz als Roh- und Werkstoff 61 (2003) 291–298 Ó Springer-Verlag 2003 DOI 10.1007/s00107-003-0393-6 291 Published online: 3 July 2003 G. Castro (&) Istituto di Sperimentazione per la Pioppicoltura [Poplar Research Institute], Strada per Frassineto 35, 15033 Casale Monferrato (AL), Italy E-mail: castro@populus.it F. Paganini (&) Istituto per la Tecnologia del Legno—C.N.R. [Wood Technology Institute], Via Biasi 75, 38010 San Michele all’Adige (TN), Italy E-mail: paganini@ivalsa.cnr.it Originalarbeiten Æ Originals