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GL Beams Reinforced with Plywood in the Outer Layer
Glulam beams are increasingly used in the construction industry because of their high strength and the possibility of using round timber with smaller cross-sections. The load-bearing capacity of beams is strongly related to the quality of the outer layers and, in the case of wood, especially the tension zones. For these reasons, this study decided to replace the outer lamella with tensile plywood. The produced beams were subjected to static bending strength and modulus of elasticity evaluation. It was shown that the best static bending strength values were obtained for beams containing plywood in the tension layer. However, the change in structure in the tension zone of beams made of glued laminated timber results not only in an increase in the load capacity of elements produced in this way but also in a decrease in the range/range of the obtained results of bending strength. This way of modifying the construction of glued laminated beams allows a more rational use of available pine timber.
The effect of the tree dieback process on the mechanical properties of pine (Pinus sylvestris L.) wood
As a result of the progressing climate changes, there is an increase in the volume of pine deadwood harvested each year from Polish forests. Its presence is an important part of the forest ecosystem; however, there are some indications that the material obtained from dying trees can be characterized by lower quality and properties. Taking into account the growing issue of tree dieback, the volume of pine wood annually harvested in Poland, and the importance of wooden products from an economic standpoint, preliminary research aimed at recognizing the process and its effect on the mechanical properties was conducted. Model trees in Brzeg Forest District were selected based on the crown defoliation. The properties of wood obtained from trees representing three different categories of soundness were determined according to the relevant standards. Based on the results of density, modulus of elasticity, bending strength, and compressive strength, it was found that there were statistically significant differences in wood quality depending on the condition of the tree. The results were particularly interesting in the case of compressing strength, where a healthy tree of lower density showed a similar strength to a dying tree with a much higher density.
The Application of Various Bark Species as a Fillers for UF Resin in Plywood Manufacturing
The aim of the presented study was to apply various bark species (birch, beech, maple, pine and spruce) as fillers for urea-formaldehyde (UF) resin in three-layer plywood manufacturing. For this purpose, all types of bark were ground and added to the adhesive mixture. The resultant plywood was subjected to investigations of the following: tensile strength, modulus of elasticity (MOE), bending strength (MOR) and formaldehyde emission. The results indicate a reduction in the tensile strength. Moreover, the lack of significant improvement in strength parameters can be explained by too high a load of the filler (20 wt%). In the case of formaldehyde emissions, a reduction was observed for birch (B-1), beech (B-2), maple (B-3) and pine bark (B-4). In addition, an increase in the emission of formaldehyde was recorded only for spruce bark.
Annual Plants and Thermoplastics in the Production of Polymer and Lignocellulose Boards
This study investigated the mechanical, physical, and thermal properties of three-layer particleboards produced from annual plant straws and three polymers: polypropylene (PP), high-density polyethylene (HDPE), and polylactic acid (PLA). The rape straw (Brassica napus L. var. Napus) was used as an internal layer, while rye (Secale L.) or triticale (Triticosecale Witt.) was applied as an external layer in the obtained particleboards. The boards were tested for their density, thickness swelling, static bending strength, modulus of elasticity, and thermal degradation characteristics. Moreover, the changes in the structure of composites were determined by infrared spectroscopy. Among the straw-based boards with the addition of tested polymers, satisfactory properties were obtained mainly using HDPE. In turn, the straw-based composites with PP were characterized by moderate properties, while PLA-containing boards did not show clearly favorable properties either in terms of the mechanical or physical features. The properties of straw–polymer boards produced based on triticale straw were slightly better than those of the rye-based boards, probably due to the geometry of the strands, which was more favorable for triticale straw. The obtained results indicated that annual plant fibers, mainly triticale, can be used as wood substitutes for the production of biocomposites. Moreover, the addition of polymers allows for the use of the obtained boards in conditions of increased humidity.
Properties of Particle Boards Containing Polymer Waste
Nowadays, a significant increase in interest in renewable energy sources can be observed. Wind farms have been one of the solutions representing this trend for many years. One of the important elements of windmills is the blades. The data indicate that what to do with the blades after their use is a global problem, and so it is important to find a way to recycle them. Hence, this work aimed to use these blades in the production of wood-based materials. Two fractions of a fragmented blade were used for the tests: a small one and large one. Boards characterized by densities of 650 kg/m3 and 700 kg/m3 were produced, in which the assumed substitution of the wood material with a polymer was 20% or 40%. Mechanical properties such as bending strength (MOR), modulus of elasticity (MOE), and internal bond strength (IB) were investigated. The 2S65 variant achieved the highest static bending strength and a modulus of elasticity of 2625 N/mm2. The second best result was noted for the 4S65 variant, which was significantly different from the 2S65 variant. In the case of the variants with a density of 700 kg/m3, no significant differences were found and their results were significantly lower. Moreover, research on thickness swelling (TS) after 24 h of immersion and water absorption (WA) were also conducted. The obtained results indicate that the manufactured boards are characterized by good physical and mechanical properties.
The Effect of Periodic Loading of Glued Laminated Beams on Their Static Bending Strength
Engineered wood products (EWP) such as glulam beams are gaining more and more popularity due to several advantages resulting from the wood itself, as well as the constant search for structural materials of natural origin. However, building materials face some requirements regarding their strength. Thus, the study aimed to assess the static bending strength of structural beams produced with the use of pine wood, after the periodic loading of approximately 80 kN for a year. The manufactured beams differed in the type of facing layers, i.e., pine timber with a high modulus of elasticity and plywood. The produced beams, regardless of their structure, are characterized by a similar static bending strength. Moreover, it has been shown that the loading of beams in the range of about 45% of their immediate capacity does not significantly affect their static bending strength and linear modulus of elasticity.