Physical Aspects of Wood Adhesive Bond Formation with Formaldehyde Based Adhesives. Part III. The Creep Behavior of Formaldehyde Based Resins at Different Relative Humidities

Holzforschung ◽  
1991 ◽  
Vol 45 (1) ◽  
pp. 69-74 ◽  
Author(s):  
M.A. Irle ◽  
A.J. Bolton
Keyword(s):  
Creep Behavior ◽  
Bond Formation ◽  
Adhesive Bond ◽  
Wood Adhesive

scholarly journals Study of Zn6Al6Ag Alloy Application in Ultrasonic Soldering of Al2O3–(Al/Al2O3) Joints

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 343 ◽  
Author(s):  
Roman Kolenak ◽  
Igor Kostolny ◽  
Jaromir Drapala ◽  
Paulina Babincova ◽  
Matej Pasak
Keyword(s):  
Ceramic Composite ◽  
Bond Formation ◽  
Adhesive Bond ◽  
Eutectic Structure ◽  
Joint Shear Strength ◽  
Al2o3 Ceramic ◽  
Metal Ceramic ◽  
Solder Microstructure ◽  
Ultrasonic Soldering ◽  
Al Matrix

The aim of this research is to characterize the soldering alloy Zn6Al6Ag, and to study the ultrasonic soldering of an Al2O3/metal–ceramic composite (Al/Al2O3). Zn6Al6Ag solder presents a quasi-eutectic structure with a melting point around 425 °C. The solder microstructure consists of a (Zn) + (Al) matrix, reinforced with a silver AgZn3 phase. A bond with the metal–ceramic composite was formed due to the dissolution of Al in the liquid Zn solder. The Al2O3 particles were put into motion, and a new composite was formed on the boundary. The Zn6Al6Ag solder also wetted the surface of the Al2O3 ceramic. A decisive effect on bond formation was caused by zinc and aluminum, whose oxides were combined with the oxides of ceramic material during in-air soldering. An adhesive bond was formed. The average joint shear strength of Al2O3/metal–ceramic composite (Al/Al2O3) was found to be 23 MPa.

scholarly journals Wood-adhesive bond loaded in mode II: experimental and numerical analysis using elasto-plastic and fracture mechanics models

Holzforschung ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Václav Sebera ◽  
Jaka Gašper Pečnik ◽  
Boris Azinović ◽  
Jaromír Milch ◽  
Sabina Huč
Keyword(s):  
Strain Energy Release ◽  
European Beech ◽  
Adhesive Bond ◽  
Wood Adhesive ◽  
Plastic Behavior ◽  
Fe Model ◽  
Maximal Force ◽  
Longitudinal Specimen ◽  
Cohesive Models ◽  
The Impact

AbstractThe goal of the study was to analyze fracture properties of adhesive bond using a three-point end-notched flexure test and the compliance-based beam method. Critical strain energy release rates (GIIc) and cohesive laws were obtained for adhesive bonds made of European beech (Fagus sylvatica L.) and adhesives such as EPI, MUF, PRF and PUR. The experiments were assisted with FE analyses employing three different material models of wood: elastic (Elas), symmetric elasto-plastic (EP) and elasto-plastic with different compressive and tensile yield stresses parallel to fiber (EP+). The highest mean GIIc was achieved for PUR (5.40 Nmm−1) and then decreased as follows: 2.33, 1.80, 1.59 Nmm−1 for MUF, EPI, and PRF, respectively. The failure of bondline was brittle and occurred at bondline for EPI, MUF and PRF, and ductile and commonly occurring in wood for PUR adhesive. The FE simulations employing cohesive models agreed well with the experimental findings for all adhesives. FE model with Elas material was found accurate enough for EPI, MUF and PRF adhesives. For PUR adhesive, the model EP+ was found to be the most accurate in prediction of maximal force. The impact of friction between lamellas may be up to 4.2% when varying friction coefficient from 0 to 1. The impact of the grain angle distortion (α) with respect to longitudinal specimen axis showed its high influence on resulting stiffness and maximal force. It was found that three-point end-notched test is suitable for EPI, MUF, and PRF, while it is less appropriate for a bond with PUR adhesive due to notable plastic behavior.

scholarly journals Cadherin puncta are interdigitated dynamic actin protrusions necessary for stable cadherin adhesion

2021 ◽  
Vol 118 (24) ◽  
pp. e2023510118
Author(s):  
John Xiao He Li ◽  
Vivian W. Tang ◽  
Kingsley A. Boateng ◽  
William M. Brieher
Keyword(s):  
Cell Adhesion ◽  
Cell Surface ◽  
Actin Polymerization ◽  
Molecular Mechanisms ◽  
Bond Formation ◽  
Adhesive Bond ◽  
Lateral Membrane ◽  
Strong Adhesion ◽  
Membrane Adhesion ◽  
Actin Protrusions

Cadherins harness the actin cytoskeleton to build cohesive sheets of cells using paradoxically weak bonds, but the molecular mechanisms are poorly understood. In one popular model, actin organizes cadherins into large, micrometer-sized clusters known as puncta. Myosin is thought to pull on these puncta to generate strong adhesion. Here, however, we show that cadherin puncta are actually interdigitated actin microspikes generated by actin polymerization mediated by three factors (Arp2/3, EVL, and CRMP-1). The convoluted membranes in these regions give the impression of cadherin clustering by fluorescence microscopy, but the ratio of cadherin to membrane is constant. Nevertheless, these interlocking fingers of membrane are important for adhesion because perturbing their formation disrupts cell adhesion. In contrast, blocking myosin-dependent contractility does not disrupt either the interdigitated microspikes or lateral membrane adhesion. “Puncta” are zones of strong cell–cell adhesion not due to cadherin clustering but that occur because the interdigitated microspikes expand the surface area available for adhesive bond formation and increase the asperity of the cell surface to promote friction between cells.

Stereomicroscopic optical method for the assessment of load transfer patterns across the wood-adhesive bond interphase

Holzforschung ◽  
2015 ◽  
Vol 69 (5) ◽  
pp. 653-660 ◽  
Author(s):  
Matthew Schwarzkopf ◽  
Lech Muszyński
Keyword(s):  
Mechanical Properties ◽  
Load Transfer ◽  
Mechanical Performance ◽  
Adhesive Bond ◽  
Wood Adhesive ◽  
Surface Strain ◽  
Image Correlation ◽  
Optical Measurements ◽  
Experimental Methodology ◽  
Full Field

Abstract The mechanical performance of wood-based composites is determined by the mechanical properties of their individual components and the effective load transfer between these components. In laminated wood composites, this load transfer is facilitated by the adhesive bond. The experimental methodology developed in this study measures and analyzes the full-field deformation and strain distributions across the loaded wood-adhesive interphase at a micromechanical level. Optical measurements were performed based on the principles of digital image correlation by a stereomicroscopic camera system. This system allows the monitoring of in-plane deformations as well as out-of-plane displacements, providing full-field 3D surface strain maps across the adhesive bond. These measurements can be used to improve the understanding of the load transfer between the adherents and the contribution of the adhesive to the mechanical properties of the bulk composite and serve as a quantitative input for numerical modeling and simulations aimed at the improvement of the products.

Isocyanate-Wood Adhesive Bond

1995 ◽  
Vol 49 (2) ◽  
pp. 171-176 ◽  
Author(s):  
F. William Weaver ◽  
Noel L. Owen
Keyword(s):  
Moisture Content ◽  
Wood Flour ◽  
Adhesive Bond ◽  
Wood Adhesive ◽  
Phenyl Isocyanate ◽  
Saturation Point ◽  
Wood Polymer ◽  
Carbamate Group ◽  
Reaction With Water ◽  
Sugar Derivatives

We have used infrared spectroscopy to study the reaction between phenyl isocyanate and glucose, cellulose, lignin, and wood. In the latter instance we have investigated oven-dried wood, wood at its fiber saturation point, and wood at 19% and 7% moisture levels. Our results show that the isocyanate reacts with all these entities, but that its reaction with water is quicker than with any of the other hydroxyl-containing compounds, and when water is present the water-isocyanate reaction dominates all others. Lignin was found to react more readily than any of the sugar derivatives. In oven-dried wood, the presence of strong new absorptions at 1712 and 1694 cm−1 (indicative of a carbamate group) is evidence of a direct chemical bond between the isocyanate and the wood polymer structure. We have also studied the reaction between 4,4′-diphenylmethane diisocyanate (MDI)—a commercially used adhesive—with wood flour at various levels of moisture content (MC), and the infrared spectra again support the presence of a wood-isocyanate bond for oven-dried wood and for wood at 7% moisture content. For wood at higher moisture content levels, our infrared results suggest that the isocyanate reacts with the water in preference to the wood polymers.

Nanoindentation mapping of a wood-adhesive bond

2007 ◽  
Vol 88 (2) ◽  
pp. 371-375 ◽  
Author(s):  
J. Konnerth ◽  
A. Valla ◽  
W. Gindl
Keyword(s):  
Adhesive Bond ◽  
Wood Adhesive

Detection of failures of adhesively bonded joints using the acoustic emission method

Holzforschung ◽  
2005 ◽  
Vol 59 (2) ◽  
pp. 219-229 ◽  
Author(s):  
Cezary Gozdecki ◽  
Jerzy Smardzewski
Keyword(s):  
Acoustic Emission ◽  
Acoustic Emissions ◽  
Adhesive Bond ◽  
Acoustic Signals ◽  
Wood Adhesive ◽  
Adhesive Joints ◽  
Structural Defects ◽  
Adhesive Bonds ◽  
Tangential Stresses ◽  
Characteristic Points

Abstract Wooden glued constructions require touch-free monitoring of destructive processes, especially in adhesive bonds that are most exposed to failure. The objective of the investigations was to describe failure processes in the adhesive bond of wood joints, in particular to determine their initiation, propagation, and destruction. The acoustic emission (AE) method was employed as the carrier of information about changes occurring in glued joints, whereas the numerical method was applied to determine values of distribution of tangential stresses generated in adhesive bonds. The acoustic phenomena examined were described using the AE cumulative counts. The authors analysed acoustic signals generated in loaded wooden and plastic overlap samples glued together using polyethyl methacrylate glue as well as in solid samples. On the basis of the acoustic emissions obtained, it was possible to establish characteristic places and stages of escalating structural defects generated from bonds of adhesive joints. This was utilised later on, in conjunction with results of numerical calculations, to determine correlations occurring between the AE cumulative counts and generated tangential stresses. Dependencies established in this way were used to determine characteristic points during the propagation of destructive phenomena of wood adhesive joints. The results obtained proved that it was possible to predict the development of the destruction of wood adhesive joints on the basis of observations of the increasing AE cumulative counts of acoustic signals in combination with tangential stresses determined using the finite elements method.

Sign in / Sign up

Export Citation Format

Share Document