Search Results (4)

The use of veneer composites as structural components in engineering requires special design. The dimensioning of laminated wood can be optimized by varying the wood species, veneer thickness, orientation, arrangement, number of single layers, and other factors. Composite properties can be calculated using suitable model approaches, such as the classical laminate theory. Thus, an optimization can be achieved. The present study verified the adaptability of the classical laminate theory for veneer composites. Native veneer, adhesive-coated veneer, and solid wood were investigated as raw materials for the plywood layers. Mechanical properties were determined using tensile and shear tests and used as parameters to calculate the composite properties of the plywood. The adhesive coating results in an increase in stiffness and strength compared with the native veneer parameters, which is greater perpendicular to the fiber than in the fiber direction. The increase due to the adhesive decreases with increasing veneer thickness. The plywood was bending tested. The measured Young’s modulus was in the range of 8000–10,700 MPa, the shear modulus was in the range of 500–1100 MPa, and the strength was in the range of 70–100 MPa. The values obtained were compared to the calculations. The best prediction of the plywood properties is obtained by using the properties of the adhesive-coated veneer as a single layer. Full article

Cutting, as the most widely used machining process, is applied in both primary and secondary wood processing. Optimum cutting conditions that result in the high quality of the machined surface and low energy consumption are crucial for wood processing. The effects of the feed speed, cutting speed and average chip thickness on the energy consumption and surface temperature of a circular saw blade during the cutting process of two types of plywood with a thickness of h = 14 mm is described in this paper. In experimental measurements, two circular saw blades with cutting tungsten carbide inserts for wood were used as tools. One circular saw blade was standard, and was not surface treated (CSB1), and second circular saw blade (CSB2) differed by the powder coating surface and the length of the cutting edge. In the experiment, the energy consumption and the surface temperature of the circular saw blade was measured in order to find the optimal cutting conditions for the most energy-efficient cutting process. The results show that the cutting power and the surface temperature of the circular saw blade increased when the feed speed increased. The investigated values of the surface-treated circular saw blade were lower compared to the values of the standard circular saw blade. When comparing the lightweight plywood with the classic plywood, experimentally obtained cutting power values of the circular saw were made 19% lower on average by using the circular saw blade CSB1. When using the CSB2 circular saw blade, these values of the cutting power of the circular saw were 22% lower on average. The surface temperature of the circular saw blade is the highest on the outer edge (tooth root area 31.7 °C) and decreases towards the center of the circular saw blade. There must be a reasonable compromise between machine productivity and energy consumption. Full article

This study investigated the impact of the design of wall systems, mainly made of compressed earth blocks (CEB), on the indoor thermal comfort of naturally ventilated housing in hot climates of Burkina Faso. Conventional housing was modeled and calibrated using the WUFI^® Plus dynamic simulation tool based on typical field surveys and the literature. This allowed testing the ability of different wall designs to impact thermal comfort. Thermal discomfort was assessed through an adaptive approach and was based on the annual weighted exceedance hours of overheating. Six designs of walls made of CEB and other locally available materials were simulated and compared to those made of classical hollow concrete blocks. The results of the simulation reveal that the profiles of thermal discomfort vary depending on the wall designs and building spaces. Thus, the wall made, from the outside toward the inside surface, of plywood of 2 cm, an insulation layer of 5 cm and a CEB layer of 29 cm thickness is the most suitable for an annual reduction in overheating for the living room. Regarding the bedroom, the most suitable wall is made of a 14 cm CEB layer, 5 cm insulating layer and 2 cm wood layer from the outside toward the inside surface. Full article

The aim of this study is to investigate the performance of casein-based adhesives for the bonding of ash (Fraxinus spp.) veneers for the manufacture of biodegradable skis. Different formulations containing casein powder, water, lime, sodium silicate, and various glue amounts were tested for shear strength after water storage, modulus of rupture and modulus of elasticity, water absorption, and thickness swelling. Two other classic wood adhesives, namely epoxy and polyvinyl acetate (PVAc) type D4 were used as control. The highest efficiency of both mechanical and physical properties was recorded for the samples glued with caseins and an increased amount of lime. There was also an affinity between casein adhesive distribution and physical and mechanical plywood performance. Moreover, the developed casein-based glues were also used to bond the plywood for ski cores and tested in real-life winter conditions. Full article