Finger-jointing of green Eucalyptus globulus L. wood with one-component polyurethane adhesives

The use of glued finger joint in green wood, directly from the sawing process, would open the possibility to obtain glued timber from small-sized wood, achieving an efficient use of the original raw material. The gluing of finger-jointed green wood, with moisture content above the fibre saturation point, may improve the efficiency and the manufacturing process of glulam or joinery. This may be especially beneficial for a hardwood such as Eucalyptus globulus L., which is a globally important forest resource, but is a challenging wood to dry. This article presents a study on the possibility to develop finger joints with wood in green state. To compare them, conventional finger joints on dry wood and solid boards without end joints were also manufactured. Cold-setting and fast-curing commercial one-component polyurethane adhesive systems were used. Finger-jointed samples were tested to determine mean and characteristic values (5th percentile) of density, bending strength and modulus of elasticity, and the results were analysed and discussed. Green-glued joints showed no statistically significant differences compared to the solid boards and improved strength properties with respect to dry-glued joints.

NUMERICAL AND EXPERIMENTAL MODAL ANALYSIS OF A CARBON FIBRE MONOCOQUE

This paper deals with the comparison of experimental measurements and numerical simulation of the natural frequency and natural shape of a carbon fibre monocoque. This comparison is used to validate the numerical analysis with a real monocoque. Usually, monocoques consist of orthotropic materials like carbon fibre sandwich with a honeycomb core. The monocoque is manufactured by hand from several layers of different materials, which are connected by glued joints. This does not guarantee the material properties or the same mass the idealized numerical simulation.

RESEARCH OF PROPERTIES OF GLUES AND GLUE BINDING, MADE WITH USE OF MODERN DOMESTIC COMPONENT BASE

Properties of epoxy glues of cold curing VK-9 and VKV-9, the components received with use which are let out by modern producers, depending on the filler used in their structure are considered. Tests of glued joints on VK-9 glue in wider interval of temperatures are carried out. Properties of VK-36 glue and its updating’s on the basis of components let out now are shown. Properties of glue binding brands VSK-14-1, VSK-14-2, VSK-14-4, VSK-14-4m and VSK-14-4k received, under production conditions by VIAM Federal State Unitary Enterprise are given. It is shown that on the properties they completely meet the requirements of existing normative documentation.

Methods for diagnosing defects in glued joints - a methods review

The paper presents the applications of glued joints in many industry branches. The advantages and disadvantages of glued joints as well as the methods of detecting weld damage are presented. The methods of damage analysis to the glued joints were divided and explained. The most important detection techniques are the X-ray method, the ultrasonic method, the Laser Ultrasound method, the guided wave method, the electromechanical impedance method and the active thermography method. The advantages and limitations that may allow for the proper selection of the research method depending on the diagnosed material and the conditions accompanying the study were indicated.

TESTING OF GLUED JOINTS ON PLASTIC PARTS MANUFACTURED USING FFF TECHNOLOGY

The article focuses on the testing of glued joints of plastic parts manufactured by 3D rapid prototyping, using the Fused Filament Fabrication technology. The first part of the article describes the suitability of using a glued joint. Then follows a brief description of the plastic materials used for the manufacturing of the testing samples. The materials include not only the common types, such as Polylactide, Polyethylene Terephthalate, Acrylonitrile Butadiene Styrene, but also Thermoplastic Polyurethane, which has a high elasticity and is usually described as a flexible material. The main section of the article deals with the testing of glued joints on a tensometric machine, which produces stress-strain curves. The shear strength of the joints is evaluated. For each material, multiple samples are prepared with different orientation of individual layers created by the 3D printing process. The impact of the orientation of the layers on the resulting strength of the glued joint is also evaluated. The final section of the article presents comparison and evaluation of the results –analyses of cracks, the impact of the orientation of the layers and the impact of individual materials. The experiment proved the independence of the orientation of the layers on the strength of the glued joint. It was also found out during the experiment that the use of a common adhesive on a flexible material was unsuitable.

Analysis of Longitudinal Timber Beam Joints Loaded with Simple Bending

The joints in timber structures are often the decisive factor in determining the load-bearing capacity, rigidity, sustainability, and durability of timber structures. Compared with the fasteners used for steel and concrete structures, fasteners for timber structures generally have a lower load-bearing capacity and rigidity, with the exception of glued joints. Glued joints in timber structures constitute a diverse group of rigid joints which are distinguished by sudden failure when the joint’s load-bearing capacity is reached. In this contribution, the load-bearing capacity of a longitudinal joint for a beam under simple flexural stress is analyzed using glued, double-sided splices. Joints with double-sided splices and connecting screws were also tested to compare the load-bearing capacity and rigidity. A third series of tests was carried out on joints made using glued double-sided splices augmented with screws. The aim of this combined joint was to ensure greater ductility after the load-bearing capacity of the glued splice joint had been reached.

Analysis of modern composite materials used in the manufacture of model kits for small-scale foundry production, obtained using bonding technology

The article presents modern data on the materials used to create model kits, the method of their installation for use on any foundries, specializing in the repair and creation of castings by experimental or small-scale batches. The analysis of the used materials, adhesive compositions for their fastening, as well as economic indicators of the costs necessary for their production was made. The properties of glued joints used for manufacturing components of model kits from plastics and its combinations with metal parts are shown.

Methodology and device to obtain torsional shear strength of glued joints

This paper presents a methodology to obtain the shear strength of glued joints, at the torsion moment. In the current standards this strength is measured by compression tests. The device designed for this purpose are also presented. The motivation for this test is related to the possibility of execution of glued wooden structures with joints under bending moment, shear force and normal force simultaneously. It was admitted the hypothesis that the joint strength can be different depending on the test type. The methodology is relatively simple and in order to obtain the results classic equations from Mechanics of Materials were used. The strength results of 198 test specimens, tested by standard methodology, were compared, with an equal number of specimens made and tested with the proposed methodology, resulting in 396 tests. 208 specimens were glued with resorcinol-formaldehyde and 188 with castor oil-based adhesive. The wood used was Eucalyptus sp. The specimens were made according to seven series involving gluing with the following angles between the fibers: 0°, 15°, 30°, 45°, 60°, 75° and 90°. Regardless of the adhesive type, there was a significant difference for the strengths presented by the two methods. From the seven angles studied, it was noticed a difference in six of them, except for the 30° series. The compression shear strength was severely affected by the gluing angle, with increasing losses towards higher angles. On the contrary, the strength offered by the joints tested by torsion did not seem affected by the gluing angle.Keywords: wood; adhesive; characterization; procedure.