Abstract
In this research, some practical aspects of densified wood glulam were investigated. For this aim, poplar wood specimens were densified by hygro-thermo-mechanical technique. Glulam specimens were produced by finger joint technique and polyurethane glue was used as resin. Physical and mechanical properties of glulams were investigated according to ASTM D 143-09, ASTM D 905-03 and ISO 8375 standards. Based on obtained results, using this process (steam and pressurize compaction) resulted in improvement of physical and mechanical properties of glulam specimens. Optical microscopic and scanning electron microscopic (SEM) pictures were proved structural changes on wood material during of applied technique. Generally, the increase of wood density and hygrothermal treatment has a positive role on the glulam properties especially its dimensional stability. This technique showed a significant effect on water absorption; the steaming temperature and holding time significantly decreased water absorption but densification process increased this parameter. Also, delamination of specimens was decreased by hygrothermal treatment while densification showed negative effect on delamination. Moreover , modulus of rupture, modulus of elasticity, shear strength and compression strength parallel to grain were decreased by this technique but it is depend to treatment temperature and holding time. Higher temperature and holding time cause to higher decrease in the glulam mechanical strength.
Highlights
Considering environmental sustainability, using renewable materials like wood timber and other wood products for building construction have major priority than other materials
The results showed that wood densification based on the compression sets (C.S.) of 40% and 60% significantly increased the glulam density in controls and treated specimens due to increment of wood material in equal volume (Fig. 2)
The results showed that steaming temperature, holding time as well as compression set had significant effect on water absorption after 24, 48 and 72 h soaking in water
Summary
Considering environmental sustainability, using renewable materials like wood timber and other wood products for building construction have major priority than other materials. Glue laminated timber (glulam) is one of the most popular and most used type of engineered wood products in recent years [1]. This product is made from sawn lumber lamina glued together in horizontal layers, using scarf or finger joints to provide the desired length [2]. Sawn lumber laminations bonded together with a resin, so that the grain of all layers runs parallel with the longitudinal direction [3]. Glulam can be made from small-diameter timber and provide high strength and large spans in architectural designs and other applications. In order to enhance the bearing capacity of structural components, save materials, and reduce cost, a glulam that is theoretically suitable
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