Glued Joints Research Articles

Investigation of the Influence of Aluminosilicate Adhesives Modified with Magnesite on the Strength Properties of Glued Wood Products

The work is devoted to the study of magnesite influence on the strength properties of glued wood products with aluminosilicate adhesive. It they shown that the introduction of magnesite in the composition of aluminosilicate glue in the amount from 0.5 to 1.5 % contributes to an increase in the shear strength along the fibres by 1.57 times compared to the normative requirement (not less than 4 MPa). It we found that the bending strength of glued wood on a toothed spike is 1.4 times higher than the normative (not less than 26 MPa). After fire tests, no destruction of the glue joint on the spike we observed, and the bending strength of the samples increases proportionally to the introduction of magnesite in the glue composition. Water resistance of glue joints on the toothed spike when the samples we kept for 48 hours at the temperature 20 °С is higher than the standard value and increases with the increase of magnesite content in the glue composition. After boiling at the temperature 100 °С for 3 hours the samples containing 1.5 % magnesite meet the normative requirements (3 MPa).

Prediction of the tensile strength of a tropical wood species Terminalia superba assembled by gluing: a comparative intelligent study

ABSTRACT The present study deals with the prediction of the strength of the glue joint stressed in tension on a local wood species called Terminalia Superba (Fraké) assembled according to the bevel configuration using two artificial intelligence models namely ANFIS and LSTM. The experimental data obtained during tensile tests on a tropical species allowed us to determine the mechanical properties taken as structural parameters for the LSTM and ANFIS models. The results of the analysis show that among all the LSTM methods, LSTM ‘ADAM’ offers a low root mean square error (RMSE), a high accuracy (Acc) (RMSE = 2.16, Acc = 0.756). For all methods, ANFIS obtained the best results, a high R-squared and a very low root mean square error (RMSE) (R-squared = 0.979, RMSE = 0.51). This indicates that the prediction of the tensile strength of the adhesive joint is more satisfactory with ANFIS than with LSTM.

Burning Properties of Combined Glued Laminated Timber

This study delved into the combustion properties of combined glulam bonded using polyurethane (PUR) and resorcinol-phenol-formaldehyde (RPF) adhesives. The experiment involved three distinct wood species, namely, spruce, alder, and beech, which were combined in homogeneous, non-homogeneous symmetrical, and non-homogeneous asymmetrical arrangements. These species were selected to represent a spectrum, namely, softwood (spruce), low-density hardwood (alder), and high-density hardwood (beech). The varying combinations of wood species illustrate potential compositions within structural elements, aiming to optimize mechanical bending resistance. Various parameters were measured during combustion, namely, the heat release rate (HRR), peak heat release rate (pHRR), mass loss rate (MLR), average rate of heat emission (ARHE), peak average rate of heat emission (MARHE), time to ignition (TTI), and effective heat of combustion (EHC). The findings indicate that incorporating beech wood into the composite glulam resulted in an increase in heat release, significantly altering the burning characteristics, which was particularly evident at the second peak. Conversely, the use of spruce wood exhibited the lowest heat release rate. Alder wood, when subjected to heat flux at the glued joint, displayed the highest heat emission, aligning with the results for EHC and MARHE. This observation suggests that wood species prone to early thermal decomposition emit more heat within a shorter duration. The time to ignition (TTI) was consistent, occurring between the first and second minute across all tested wood species and combinations. Notably, when subjected to heat flux, the glulam samples bonded with PUR adhesive experienced complete delamination of the initial two glued joints, whereas those bonded with RPF adhesive exhibited only partial delamination.

Digital image processing in the determination of glued wood joints behavior

The determination of the efficiency of adhesives applied in glued joints, through the analysis of the percentage of wood failure, is one of the main validation parameters for the quality of gluing techniques and adhesive. However, the subjectivity of the interpretation, performance, and visual acuity of the evaluators makes the methodology subjective. This research aimed to establish a method for evaluating the behavior of the glue line in glued joints, using freely available software and digital camera images. Shear samples of glued joints with polyvinyl acetate - PVAc, resorcinol formaldehyde - RF, and melamine formaldehyde - MF were evaluated using digital images obtained by a 16.1-megapixel camera. The images were pre-processed to enable vectorization in Inkscape software, version 1.1.2. Each image was vectorized and subjected to the measurement of the areas of the generated vector layers (glue line and wood). The validation process was performed by evaluating the accuracy of vectorization. Thus, the photograph of each sample and the vectorized image were imported into ImageJ software, version 1.53. To ensure the reliability of the proposed methodology, statistical analyses of the Kappa coefficient, global accuracy, user, and producer were applied. To evaluate the efficiency of the proposed method in relation to the conventional method provided in ASTM D5266-13, five evaluators analyzed the proportion of bond line and wood failure of the 10 samples submitted to the proposed methodology. Subsequently, a descriptive analysis of the data was carried out to evaluate the variability and subjectivity of the conventional analyses among the evaluators. It is noted that the proposed methodology achieved high efficiency in the analysis of the proportion of glue line and wood, and it can be assured by the accuracy tests performed. The research also showed that there was no agreement among the five evaluators using the conventional method. It is concluded that the proposed methodology meets the research objective, with high levels of accuracy, and confirms the subjectivity of the analyses performed with the conventional methodology. The results underscore the need for objective methodologies, employing computational techniques to reduce subjectivity in adhesive bond failure assessments, enhancing critical decisions in the selection of adhesives for industrial structural applications.

Научное обоснование использования древесины осины в деревянных клееных конструкциях

One of the promising materials for construction are wooden glued structures. According to the current regulatory documents, for the production of such structures coniferous wood is usually used, the reserves of which in industrially developed areas have significantly decreased over the last decades. At the same time, in a number of regions of Russia there is a significant raw material reserve of aspen wood, which has been successfully used in the construction of buildings and structures for many centuries. Its physical and mechanical characteristics differ from pine wood from 3.2 to 18.6 %. Therefore, it can be considered as an alternative source of raw materials for wooden house construction enterprises. To assess the degree influence of the combination of coniferous and aspen wood on the strength of the glue joint, as one of the main indicators of the quality of wooden glued structures, a set of theoretical and experimental studies was carried out. Maximum tangential and normal stresses of glue joint in pine and aspen blanks, which are significantly higher than those of solid wood, were determined by calculation. The values of shear strength in glued pine and aspen lamellas (4.46–8.06 MPa), obtained during the experiments at the 1st stage of research, were close to the strength of solid wood. At the 2nd stage the method of dispersion analysis was used, the results confirmed the assumption that when gluing lamellas up to 20 mm thick, the difference in the strength of the glue joint of structures made of pine and structures made of pine and aspen is insignificant. The obtained data serve as a basis for further work on diversification of raw material resources in the production of wooden glued structures due to the involvement of low-demand aspen wood in processing. For citation: Titunin A.A., Gevorgyan M.S., Fedotov A.A., Vakhnina T.N., Susoeva I.V. Scientific Substantiation of Aspen Wood Use in Wooden Glued Structures. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 6, pp. 149–161. (In Russ.). https://doi.org/10.37482/0536-1036-2023-6-149-161

Deformation Properties of an Elastic Adhesive in Glue Joints under Quasi-Static Low-Cycle Mechanical Loads

Deformation Properties of an Elastic Adhesive in Glue Joints under Quasi-Static Low-Cycle Mechanical Loads

Using a non-linear mixed model behavior of CZM to predict the damage in single lap bonded joint with Bi-composite graded materials

The present work is a numerical prediction based initially on a reliable model validated by experiments under the same conditions used as ours with new concepts in Bi-composite plates. A system formulation approach of the adhesive in ductile and nonlinear damage behavior is used in this analysis This ductility is developed by the CZM technique implemented using the MATLAB program in ABAQUS computer code. For a numerical prediction of the ductile behavior of the adhesive, the CZM model is an extension of the pure modes (I and II) previously characterized in block by tests. This extension is trapezoidal in increasing stresses of the adhesive in its behavior law. The single lap joint configuration allows us to stress the glue joint to mixed-mode loading. The resistance of the assembled structures remains conditioned by the behavior of the adhesive until it is damaged and the rigidity of the attached plates. Therefore, our objective in this work is to cause the plasticization damage of the adhesive at different responses and levels. For this, the bi-composite graduation in concept and in graduation index largely plays the role of evaluation parameters. In order to test the adequacy for a good resistance, three different concepts of graduation in Bi-composite were proposed such as: concept1-concept1, concept2-concept2, and simple concept-simple concept. By these two cases of assemblies, these concepts have the advantage of having different assembly possibilities, The proposed concepts of graduated bi-composite plates showed an overcapacity of resistance on the assembly. The latter becomes important in the adequacy of concept of these assembled plates. Similarly, the results show that different responses and levels cause the damage by effect of these concepts.

Study on the shear behavior of externally prestressed segmental glued concrete beams

For segmental precast assembled bridges, joints are the key to their overall strength, especially their shear strength. Using shear span ratios (1.0, 1.3, 1.6), prestress levels (0 MPa, 2 MPa, 4 MPa) and beam types (segmental beam, monolithic beam) as the influencing factors, five segmental glue joint beams and one monolithic beam were fabricated for static load tests, and the laws of the above three factors on the shear performance of externally prestressed segmental glued concrete beams were obtained. The results show that all specimens exhibited brittle failure characteristics, and the prestressed specimens had better ductility. By reducing the shear span ratio and increasing the prestress level, the shear bearing capacity and overall stiffness of the specimens were improved, and the ductility of the specimens with a low prestress level was better. The shear bearing capacity of monolithic beam was higher than that of segmental beam, but the difference between them was not significant. Based on the test results, numerical models were developed and their validity was verified.

The study of the quality of adhesive bonding of decorative elements in a multifunctional set for a girl

The article analyzes the method of adhesive bonding of finishing elements in the manufacture of garments and determines the quality indicators of strength, hardness, wear resistance and the flexibility properties of adhesive bonding of finishing materials. Improving the principles and level of development of light industry production is today's requirement. The transformation of multifunctional clothing for girls from a modern point of view opens up new constructive and artistic solutions for the compatibility of elements, creates a new composition of youth costumes. The transformation of the girls' set into a variety of clothing expands the range of consumer clothing and prolongs their wear life. One of such products is a set of multifunctional clothes for girls with adhesive decorative elements. As a result of the research, a mode for processing the adhesive bond of decorative materials was chosen and a multifunctional kit for girls was made from tested materials. In the manufacture of a set for girls with the use of finishing materials with a glue joint, it reduces the time of manufacture and improves the quality of processing, increases the competitiveness of a set for girls, decorated with decorative elements in accordance with market requirements. The multi-functional girl set, which is transformed according to consumer requirements and decorated with interchangeable elements and finishing parts, is widely used by consumers and fully meets the aesthetic and performance requirements of young people.

Experimental study on the direct shear behavior of multiple shear keys at concrete glue joints subjected to uneven normal stress

Ten ‘Z’-shaped shear specimens were fabricated to study the effect of uneven normal stress on the shear performance of glue joints. The test parameters included the roughness of the joint surface, the level of lateral normal stress, and the uniformity of lateral normal stress. The crack development, failure mode, ultimate bearing capacity, and relative slip data of the specimens were recorded in detail, and the load-strain curve and load-relative slip curve were plotted according to the test results. The results show that all specimens were brittle failures. After roughening the surfaces of the joints, the deformation resistance, overall strength, and overall stiffness of the specimens all got a little better. Increasing the level of lateral normal stress and the uniformity of lateral normal stress, the cracking load and ultimate bearing capacity of the specimen were increased. In addition, a coefficient η that quantifies the degree of uniformity of the lateral normal stress was defined, and a formula for predicting the direct shear bearing capacity of glue joints was proposed. The results show that the average ratio between the calculated values from the proposed formula and the test values was 0.96.

Parametric Investigation into the Shear Strength of Adhesively Bonded Single-Lap Joints.

In this paper, the shear strength of adhesively bonded single-lap joints were experimentally and numerically investigated. Based on the validated simulation, the effects of lap length, adhesive layer thickness, adhesive layer shape, adhesive layer overflow length, and laminate lay-up on the shear strength of adhesively bonded single-lap joints were studied. The load-displacement curves and shear strength under different parameters were compared. It was shown that the shear strength of single-lap joints gradually decreases with the increase of lap length and adhesive layer thickness, which were 53.83% and 16.15%, respectively. Considering the potential condition in fabrication, the adhesive layer shape and adhesive layer overflow length were also investigated. The adhesive with normal and triangle shape owned the comparable shear strength, which was higher than the arc one. The shear strength increased by 19.37% from 18.43 MPa to 22.00 MPa with increasing the adhesive layer overflow length to 50% of lap length. It was beneficial for shear strength to increase the adhesive layer overflow length to 50% of lap length. Among the selected four lay-ups, [0]16s had the highest shear strength, which was nearly 3 times greater than the one of [90]16s. In the real process preparation, increasing the number of 0° layers, selecting the appropriate lap length and thickness of the adhesive layer, and controlling the shape and length of the adhesive layer overflow are of great help to improve the tensile shear strength of the single-lap glue joint.

THE EFFECT OF A PHENOL-FORMALDEHYDE ADHESIVE REINFORCEMENT WITH NANOCELLULOSE ON THE PRESSING PARAMETERS OF PLYWOOD

Researchon improving the reactivity of phenol-formaldehyde (PF) resin and thepossibility of lowering the pressing parameters of wood-based materials manufactured with its participation are still progressing. Due to a number of favorable properties, nanocellulose(NCC) is gaining more and more popularity as a modifier ofwood adhesives. Therefore, theobjective of the study was to assess the possible reduction of plywood pressing parameters due to the reinforcement of PF resin with NCC. Based on the bonding quality results it was found that there is a possibility to reduce pressing time by 25% and pressing temperature by 7%. Moreover, the outcomes of mechanical properties (modulus of elasticity and bending strength) of manufactured plywood indicate that theoretically it could be possible to decrease the pressing parameters even more. However, the shear strength of the glue joints was considered to be alimiting factor for further reduction. The results of delamination test show that plywood bonded with phenolic resin have no tendency to delaminate. Thus, it can be concluded that NCC can be used as a modifier for PF resin which can contribute to the reduction of pressing time and pressing temperature during the plywood manufacturing process.

Experimental study on the shear behavior of precast concrete segmental simply supported beam with internal tendons and glue joints

Glue joints make precast concrete segmental beams with discontinuity, which is the weak link and an important part of the structure and needs to be given special attention in practical engineering. To test the shear behavior of five segmental glue joint beams and one monolithic beam, the test parameters included shear span ratios (1.2, 1.5), prestress levels (4 MPa, 6 MPa, 6.5 MPa), prestress types (unbonded prestress, bonded prestress), and beam types (segmental beam, monolithic beam). The results show that both segmental glue joint beams and monolithic beams exhibited typical brittle failure characteristics in the failure stage. The shear span ratio increased, the shear bearing capacity of the specimen decreased, and the deformation increased. The deformation of the specimen decreased when the prestress level increased. The bonded prestressed screw-thread bar improved the overall strength and stiffness of the segmental glue joint beam. The crack resistance of the monolithic beam was better than the crack resistance of the segmental glue joint beam, but the difference in shear bearing capacity between them was small. The test data were compared with the calculated values of shear bearing capacity of different formulas, and the results show that the calculated values of formulas of the American Association of State Highway and Transportation Officials (AASHTO (2003)) standard were in the best agreement with the test values. Based on the test results, the strain distribution and stress distribution of the specimens were further explored by combining the finite element method. The results show that cracks of different specimens would cross the glue joints. The yield strength of the prestressed screw-thread bar was not reached when the specimen was damaged.

Elements of Designing Upholstered Furniture Sandwich Frames Using Finite Element Method.

This paper presents an approach to the design of an upholstered furniture frame using the finite element method and empirical studies. Three-dimensional discrete models of upholstered furniture frames were developed taking into account orthotropic properties of solid pine wood (Pinus sylvestris L.) without and with details strengthening their structure in the form of glue joints and upholstery staples. Using the CAE Autodesk Inventor Nastran finite element method, linear static analyses were performed by simulating normative loading. The finite element method was performed considering the experimentally determined stiffness coefficients of the PCAC adhesive and staple joints. As a result, stress, displacement, and equivalent strain distributions were obtained for upholstered furniture frame models with stapled corner joints. The deformation and strength behavior of the upholstered furniture frames was improved by reinforcing with a wood strip. A new approach to the design of upholstered furniture frame frames using the FEM method with stapled component connections was developed and tested. The results of the study can be applied in the optimization of upholstered furniture construction.

Structural Health Monitoring of glulam infrastructures with non-destructive embedded sensors

As an answer to actual environmental challenges, wood and specifically wood composites such as glued laminated timber (glulam) became a good alternative to “traditional” building materials such as concrete or steel. However, durability issues related to its environment, especially moisture, could be a imitating factor to the development of these structures. To allow glulam to be more widely used in infrastructures such as bridges we propose an embedded structural health monitoring system, measuring durability parameters in real time. It will allow a live assessment of the condition of the structure. Glulam moisture sensitivity is characterized by biological degradations at high humidity rates or cracks, delamination and internal stresses caused by humidity variations leading to a loss of mechanical properties. An integrated system, developed during two theses, allows us to record humidity rate with patch type sensors using resistive measurement method and stresses in glue joints using strain gauges, both embedded in the thickness of the glue. We are currently conducting long term experiments in real climatic conditions with loaded and unloaded beams exposed in an outdoor application to correlate the effects of real-life wetting/drying cycles combined with duration of load effects on the mechanical properties of our test samples. The running experiment started in august 2020 with 30x30x480mm model glulam beams, we are testing the bending strength of our samples to compare our results with tests conducted in climatic chamber which showed encouraging to predict the actual condition of glulam. We plan to use our data to create a predictive model to be able to determine structural performance of glulams based on live moisture measurements. This system will allow a live mapping of humidity in glulam structures, it could help glulam structures managers in preventing moisture induced pathologies and evaluating the remaining lifespan of the glulams.

Studies on Internal Stresses within Glue Joints in Glued Wooden Structures

Studies on Internal Stresses within Glue Joints in Glued Wooden Structures

Development of bus body technologies in terms of corrosion and durability

The object of this study is the technology of bus bodies and the formation of recommendations for design bodywork subject to the regulated durability of the body introduced into production. Advancing the technology of manufacturing bus bodies implies improving anti-corrosion protection, using new polymeric materials, and reducing the length of welds. The issue of corrosion resistance of bus bodies has been considered. It is established that the use of new polymeric materials will increase the corrosion resistance of bus bodies while existing technologies weakly protect against corrosion (resource up to 5 years). The peculiarity of this study is that the adhesion of new materials has been tested, with artificial aging, which confirms the durability of glued joints. According to the old technology, the body was exposed to anticorrosive treatment after welding the cladding with uncovered places left between the frame and body cladding, which provoked corrosion. The main idea is that in the new technology, the cladding is welded or glued after the body frame is fully coated with primer. New technologies and materials not used in the automotive industry have been proposed. Three variants of technologies were put into production. First: the welding of steel zinc sheets. In welding sites, the frame is covered with conductive primer. It was implemented for school buses (after 7 years, without damage). Second: gluing steel zinc sheets. It was implemented for city buses (after 6 years, without damage). Third: gluing sheets from composite materials not used in the automotive industry. The transition to new adhesive cladding technologies from composite corrosion-resistant materials instead of steel sheet, reduces by 2.5–3 times the length of welds (up to 20 years without damage). The studies have confirmed the strength of glued joints (cohesion rupture exceeds 95 %). The reliability of glued joints and high corrosion resistance of the body have been confirmed in the operation of buses. The scope of practical use of the results: bus-building plants. The reported results are suitable for production of all types while cataphoretic coatings are only for mass production

Influence of the glue joint on the speed of propagation of sound waves in wood

Influence of the glue joint on the speed of propagation of sound waves in wood. The aim of this study is to demonstrate differences in the propagation of sound waves in wood depending on the type of glue used to form the joint. Samples of tree species considered as resonant wood, i.e. Norway spruce (Picea abies) and sycamore (Acer pseudoplatanus), and for comparison, wood of European beech (Fagus sylvatica) were used. The fractured samples were glued together using glutinous fish glue, polyurethane glue (Titebond Liquid Glue) and cyanoacrylate glue (BONDOLOC B415). All types of glue are used in instrument repair, of which glutinous glue is regarded to be the correct one used in gluing technique. The test was carried out using a non-destructive ultrasonic method. It has been shown that the highest decreases in speed of propagation of sound waves are in wood glued with glutinous glue and the lowest in wood glued with cyanoacrylate glue.

Timber‐glass composite: concepts for glued bracing floor elements

The objective of several research projects was to investigate alternative constructions of stiffening glass fronts, which replace St. Andrew's cross wind bracings and costly frameworks. These are only suitable for vertical use and for absorbing the horizontally acting forces in the directions of the panes. A follow‐up research project was started with the aim of developing calculation and design concepts for glued bracing floor and roof elements. Taking into consideration short‐term behaviour and seismic performance the practical applications considered is to develop bracing composite elements. These transparent and light‐weight elements could substitute the conventional bracing elements and/or heavy massif constructions. The research project “Timber‐glass composite: concepts for glued bracing floor and roof elements” is going to develop highly transparent and load‐bearing composite floor structures. These shall stiffen the building at floor and roof level and should be able to withstand loads in combined pane‐ and panel loading. In the research project composite timber and glass sections for load bearing and stabilizing purposes will be developed. The special feature of such a further development of existing timber‐glass composite elements is the presence of an interrupted formation of adhesive joints. The compressive stresses occurring in the glued joints will be reduced by the punctiform blocking of the glass panes. From this, a transmission of shear stresses can be achieved, which is currently only possible to a very limited extent but is absolutely necessary for use. The glass has not a stiffening bearing function, merely functions as an outer cover in the same time. For the development of new composite elements made of timber, glass and adhesives the identification of relevant material properties and setting up of requirement specifications for adhesive bonding of glass to timber is substantial and are addressed in the research project together with issues like moisture and temperature fluctuations. In order to counteract summer overheating and protect privacy, the glass elements should be equipped with switchable panes. Thus, light architecture that is integrated into the environment should still be easy to realize.

Using statistical inverse methods for detecting defects in electronic components

The thermal modeling of electronic components is mandatory to optimize the cooling design versus reliability. Indeed most of failures are due to thermal phenomena [1]. Some of them are neglected or omitted by lack of data: ageing, manufacturing issues like voids in glue or solder joints, or material properties variability. Transient measurements of the junction-to-board temperature supply real thermal behavior of the component and PCB assembly to complete these missing data[2]. To complement and supplement the numerical model, inverse methods identification based on a statistical deconvolution approach, such as Bayesian one, is applied on these measurements to extract a Foster RC thermal network. The identification algorithm performances have been demonstrated on numerical as well as experimental dataset. Furthermore defects or voids can be detected using the extracted Foster RC networks.