Fracture Mechanics of Adhesive Bonds

1974 ◽  
Vol 47 (1) ◽  
pp. 202-212 ◽  
Author(s):  
A. N. Gent
Keyword(s):  
Adhesive Joint ◽  
Unit Area ◽  
Energy Requirement ◽  
Critical Energy ◽  
Thermal Contraction ◽  
Adhesive Bonds ◽  
Adhesive Layers ◽  
Modes Of Failure ◽  
Shear Rupture ◽  
Set Up

Abstract A survey is given of the mechanics of rupture of a simple adhesive joint, comprising two relatively rigid adhering members joined by a layer of a deformable adhesive. Several different modes of failure are treated in terms of a critical energy requirement for growth by unit area of a pre-existing interfacial flaw or debond. They are: (i) Tensile rupture of joints with thick or thin adhesive layers, (ii) Shear rupture, (iii) Separation by stripping apart stiff or flexible adherends, i.e. cleavage. In addition, the stresses set up in joints by shrinkage of the adhesive, for example due to differential thermal contraction, are evaluated. Attention is drawn to probable sites and conditions for failure.

The Mechanics of Ozone Cracking

1962 ◽  
Vol 35 (1) ◽  
pp. 200-209 ◽  
Author(s):  
M. Braden ◽  
A. N. Gent
Keyword(s):  
Tensile Stress ◽  
Crack Growth ◽  
Energy Requirement ◽  
Critical Energy ◽  
Critical Value ◽  
Experimental Measurements ◽  
Rubber Sheet ◽  
Polymer Molecules ◽  
Two Factors ◽  
Applied Tensile Stress

Abstract Experimental measurements are described of the growth of a cut in a stretched rubber sheet under the action of an atmosphere containing ozone. A well-defined rate of crack growth is obtained, substantially independent of the applied tensile stress when this exceeds a critical value necessary for growth to occur at all. The rate of growth is found to be similar for a number of polymers and principally determined by the ozone concentration when the mobility of the polymer molecules is sufficiently high. When the molecular mobility is inadequate, crack growth is retarded. The critical condition is found to be similar for all the polymers examined, and largely independent of the conditions of exposure; it appears to reflect an energy requirement for growth of about 40 ergs/cm2 of newly-formed surface. The effect of the degree of vulcanization and the presence of additives, including antiozonants, on these two factors has also been examined. The dialkyl-p-phenylene diamines are found to confer protection by raising the critical energy required for growth to occur, in contrast to other protective agents which affect only the rate of crack propagation.

NON-DESTRUCTIVE EVALUATION OF MECHANICAL DAMAGE OF ADHESIVES USING MAGNETO-ELECTRIC NANOPARTICLES

2021 ◽  
Author(s):  
GONZALO SEISDEDOS ◽  
BRIAN HERNANDEZ ◽  
JULIETTE DUBON ◽  
MARIANA ONTIVEROS ◽  
BENJAMIN BOESL ◽  
...  
Keyword(s):  
Adhesive Joint ◽  
Adhesive Bonding ◽  
Mechanical Damage ◽  
Adhesive Bond ◽  
Tensile Tests ◽  
Adhesive Joints ◽  
Adhesive Bonds ◽  
Magnetic Signatures ◽  
Looper System ◽  
Lock In

Adhesive bonding has been shown to successfully address some of the main problems with traditional fasteners, such as the reduction of the overall weight and a more uniformly distributed stress state. However, due to the unpredictability of failure of adhesive bonds, their use is not widely accepted in the aerospace industry. Unlike traditional fastening methods, it is difficult to inspect the health of an adhesive joint once it has been cured. For adhesive bonding to be widely accepted and implemented, there must be a better understanding of the fracture mechanism of the adhesive joints, as well as a way to monitor the health of the bonds nondestructively. Therefore, in-field structural health monitoring is an important tool to ensure optimal condition of the bond is present during its lifetime. This project focuses on the advancement of a non-invasive field instrument for evaluation of the health of the adhesive joints. The tool developed is based on a B-H looper system where coils are arranged into a noise-cancellation configuration to measure the magnetic susceptibility of the samples with a lock-in amplifier. The B-H looper system can evaluate the state of damage in an adhesive bond by detecting changes in surface charge density at the molecular level of an epoxy-based adhesive doped with magneto-electric nanoparticles (MENs). Epoxy-based adhesive samples were doped with MENs and then scanned using the B-H looper system. To evaluate the health of the adhesive joint, microindentation and tensile tests were performed on MENs-doped adhesive samples to understand the relationship between mechanical damage and magnetic signal. Correlations between magnetic signatures and mechanical damage were minimally observed, thus future studies will focus on refining the procedure and damaging methodology.

Models of Adhesive Bonding of Hybrid Structures

2013 ◽  
Vol 550 ◽  
pp. 143-155 ◽  
Author(s):  
R. Bréthous ◽  
V. Nassiet ◽  
B. Hassoune-Rhabbour
Keyword(s):  
Low Temperature ◽  
Adhesive Joint ◽  
Adhesive Bonding ◽  
Thermomechanical Properties ◽  
Diffusion Study ◽  
Shear Tests ◽  
Stress Zone ◽  
Linear Viscoelastic ◽  
Adhesive Thickness ◽  
Set Up

Adhesives are often based on polymers materials. They are good candidates in order to manufacture adhesives joint because of their thermomechanical properties and their processing which is easier than other materials. Epoxy resins are widely used as adhesives joint. We can meet them in various industrial areas like car, spatial and aerospace domains. Because of numerous combinations between epoxy and amine chemical functions, these joints may be efficient at high or at low temperature. Indeed, close to their glassy transition temperature (Tg), exists an elastic modulus / ductility couple for which, shear stress is optimum: the Optimum Stress Zone (OSZ)[ which is restricted on limited temperatures range. Our study consists in formulating an epoxy amine joint able to be efficient on an extended temperatures rangei.e.a joint able to ensure a stress continuity over a large range of temperatures, for example-50°C to 100°C. To reach this objective, we propose an evolution of the Multi Adhesive Joints (MAJ): an adhesive joint presenting a gradient of mechanical properties. To make this adhesive joint formulation possible, its necessary to control kinetics diffusion at the adhesive scale (200μm to 500μm) between the low temperature adhesive (LTA) and the high temperature adhesive (HTA). The diffusion study will be carried out by using a rheometer. For such adhesive thickness, the rheometer compliance may have an influence on the results. Therefore, this present work proposes to identify and to set up the key parameters, which allow following kinetics diffusion in a rheometer for dimensions similar to those of bonding assembly, by checking the measurements are performed in the linear viscoelastic domain. In a first part, the morphological, mechanical and thermomechanical properties of the nanostructured thermosets versus time are performed. And, the second part will deal with the optimization of the key parameters by performing dynamic shear tests versus time on HTA and LTA samples in sight of kinetics diffusion study.

Verification of the Agricultural Research Council (1981) recommendations on energy requirement of the pregnant sow

1984 ◽  
Vol 1984 ◽  
pp. 31-31
Author(s):  
Pauline A. Lee ◽  
K.G. Mitchell
Keyword(s):  
Reproductive Cycle ◽  
Research Council ◽  
Agricultural Research ◽  
Energy Requirement ◽  
Weight Changes ◽  
Agricultural Research Council ◽  
Weight Gains ◽  
Set Up ◽  
Pregnancy Weight ◽  
The Relationship

The Agricultural Research Council (1981) states the energy requiremnets for pregnant sows in terms of amounts needed per day to ensure specific net pregnancy weight gains for differing weights at service (Table 1.). An experiment was set up primarily to test the validity of these recommendations which were derived by factorial calculations and secondly to examine the relationship between condition (P2 measurement) and weight changes over the reproductive cycle.

Effect of Bond Thickness on the Fracture Toughness of Adhesive Joints

2004 ◽  
Vol 126 (1) ◽  
pp. 14-18 ◽  
Author(s):  
Deok-Bo Lee ◽  
Toru Ikeda ◽  
Noriyuki Miyazaki ◽  
Nak-Sam Choi
Keyword(s):  
Fracture Toughness ◽  
Adhesive Joint ◽  
Damage Zone ◽  
Crack Tip ◽  
Adhesive Layer ◽  
Compact Tension ◽  
Optical Microscope ◽  
Adhesive Joints ◽  
Adhesive Layers ◽  
Modified Epoxy

The effect of bond thickness on the fracture toughness of adhesive joints was investigated from a microstructural perspective, using compact tension (CT) adhesive-joint specimens with different bond thicknesses. The adhesive material was a rubber-modified epoxy resin with 12.5 wt% carboxy-terminated butadiene acrylonitrile (CTBN) elastomer. The shapes of the rubber particles dispersed in adhesive layers of damaged and undamaged specimens were observed with an optical microscope. The damage was distributed along the interfaces between the adhesive layer and the two adherends. The results show that the primary causes of variations in the fracture toughness of an adhesive joint with the bond thickness are not only a damage zone around a crack tip but also the combination of a damage zone around a crack tip and additional damage zones along the interfaces.

Thermal Contraction of AA5182 for Prediction of Ingot Distortions

2006 ◽  
Vol 306-308 ◽  
pp. 977-982 ◽  
Author(s):  
Suyitno ◽  
Dmitry G. Eskin ◽  
Laurens Katgerman
Keyword(s):  
Numerical Simulation ◽  
Thermomechanical Behavior ◽  
Thermal Contraction ◽  
Contraction Process ◽  
Start Up ◽  
Aa5182 Alloy ◽  
Set Up ◽  
Nonequilibrium Solidification ◽  
Good Agreement ◽  
Cast Products

Shape distortions and hot cracking during casting are strongly related to thermal contraction during and after solidification. The understanding of this phenomenon is crucial in designing defect-free cast products and in numerical simulation of their thermomechanical behavior. This paper presents the results of experimental and numerical simulation work on the thermal contraction during and after solidification of a commercial AA5182 alloy. In the specially developed experimental set-up, the contraction is measured simultaneously with temperature while the material solidifies and cools down in the solid state. An elasto-viscoplastic constitutive model fitted to experimental data is used in finite element simulations of the contraction process. The implementation of thermal contraction data for ingot distortion during the start-up phase of casting is also included. The results show that the contraction starts at a certain temperature in the nonequilibrium solidification range, close to the non-equilibrium solidus. Good agreement is found between simulation and experimental results.

scholarly journals Forest ecotone survey by line intersect sampling

2004 ◽  
Vol 34 (8) ◽  
pp. 1776-1783 ◽  
Author(s):  
Piermaria Corona ◽  
Gherardo Chirici ◽  
Davide Travaglini
Keyword(s):  
Unit Area ◽  
Central Italy ◽  
Classical Approach ◽  
Visual Interpretation ◽  
Landscape Mosaic ◽  
Remotely Sensed Imagery ◽  
Ecological Relevance ◽  
Gis Environment ◽  
Set Up ◽  
Forest Ecotone

Given their ecological relevance, the survey of ecotones is of considerable interest in forest multiresource inventory. To this end, it is useful to set up survey procedures to provide efficient and reliable information about the length of such elements within the landscape mosaic. This note demonstrates a procedure based upon line intersect sampling on remotely sensed imagery. The estimate of ecotone length per unit area is obtained by visual interpretation of the changes from forest to other land use classes along each sampling line. The experimentation carried out in two test areas within forest landscapes of central Italy proves the operative soundness of the proposed procedure, which is more efficient than the classical approach by forest polygon delineation and perimeter mensuration in a GIS environment. Under the examined conditions, samples based on a moderately high number of lines characterized by relatively long length prove to be more efficient than those based on shorter survey units.

Kinetics of nitridation of calcium

1959 ◽  
Vol 251 (1266) ◽  
pp. 369-377 ◽  
Keyword(s):  
Calcium Ions ◽  
Metal Ion ◽  
Constant Pressure ◽  
Unit Area ◽  
Film Formation ◽  
Difference Set ◽  
Nitride Layer ◽  
Thin Film Formation ◽  
Set Up ◽  
Kinetics Of

The kinetics of the reaction of nitrogen with sintered, evaporated calcium films has been studied between 23 and 200°C using a constant-pressure technique. The results are consistent with a modified Mott & Cabrera theory of thin film formation, the rate being controlled by the mobility of the calcium ions through the nitride lattice under the influence of the potential difference set up between the metal and chemisorbed nitrogen at the nitride surface. The rate depends directly on the first power of the pressure suggesting a reversible adsorption to form a ‘surface complex’, N - 2 . The linear dependence of activation energy on the inverse thickness of the nitride layer is verified and the critical temperature determined. In addition, an estimation of the fraction of the total number of metal sites per unit area interface from which the metal ion penetrates the nitride layer has been made.

scholarly journals Renewable energy, sustainability paradox and the post-urban question

Urban Studies ◽  
2019 ◽  
Vol 57 (11) ◽  
pp. 2300-2320 ◽  
Author(s):  
Pushpa Arabindoo
Keyword(s):  
Renewable Energy ◽  
Energy Production ◽  
Smart Cities ◽  
Critical Energy ◽  
Energy Sustainability ◽  
Transformative Potential ◽  
New Energy ◽  
Set Up ◽  
Core Characteristics ◽  
Installed Capacity

Amidst the hype of a ‘new’ energy regime in India with a singular focus on renewable energy, this paper offers a more scrupulous reading of renewables to set up a critical energy discourse. It offers a three-part analysis where it begins by questioning the entrenched idea of ‘renewables as science’ and its instrumental use of metrics and measurements to convey an unbelievable reach and significance. Highlighting the consistent invocation of a calculative ethos, it shows how an ‘empirics of targets’ relying largely on the lure and lore of a single numeric, installed capacity, is persuasively employed to gloss over the crucial distinction between the potential and reality of renewables. An associated consequence is not only its pegging to the speculative value of market-based energy production but also that it remains rooted in the assumptions of an existing system, that is, the logic of a carbon lifeworld. Renewables, as a result, display the tell-tale sign of a sustainability paradox, raising questions about their ability to master a transition to a post-fossil performativity, exasperated as they are by internal contradictions embedded within their core characteristics – efficiency/sufficiency and, more importantly, tensions between utilities and infrastructure. With loose connections to parallel initiatives such as the Smart Cities Mission, the transformative potential of renewables is undercut as it remains embedded within an abstract grid imaginary, challenging any effort to actualise it in and through the urban.

scholarly journals Ultra-High Packing Density Next Generation Microtube Array Membrane for Absorption Based Applications

Membranes ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 273
Author(s):  
Chee Ho Chew ◽  
Wan-Ting Huang ◽  
Tzu-Sen Yang ◽  
Amanda Chen ◽  
Yun Ming Wu ◽  
...  
Keyword(s):  
Packing Density ◽  
Unit Area ◽  
Polymyxin B ◽  
The Novel ◽  
Next Generation ◽  
Rapid Reduction ◽  
Different Types ◽  
Set Up ◽  
Microtube Array ◽  
Time Point

Previously, we successfully developed an extracorporeal endotoxin removal device (EERD) that is based on the novel next generation alternating microtube array membrane (MTAM-A) that was superior to the commercial equivalent. In this article, we demonstrated multiple different parameter modifications that led to multiple different types of novel new MTAM structures, which ultimately led to the formation of the MTAM-A. Contrary to the single layered MTAM, the MTAM-A series consisted of a superior packing density fiber connected in a double layered, alternating position which allowed for the greater fiber count to be packed per unit area. The respective MTAM variants were electrospun by utilizing our internally developed tri-axial electrospinning set up to produce the novel microstructures as seen in the respective MTAM variants. A key uniqueness of this study is the ability to produce self-arranged fibers into the respective MTAM variants by utilizing a single spinneret, which has not been demonstrated before. Of the MTAM variants, we observed a change in the microstructure from a single layered MTAM to the MTAM-A series when the ratio of surfactant to shell flow rate approaches 1:1.92. MTAM-A registered the greatest surface area of 2.2 times compared to the traditional single layered MTAM, with the greatest tensile strength at 1.02 ± 0.13 MPa and a maximum elongation of 57.70 ± 9.42%. The MTAM-A was selected for downstream immobilization of polymyxin B (PMB) and assembly into our own internally developed and fabricated dialyzer housing. Subsequently, the entire setup was tested with whole blood spiked with endotoxin; and benchmarked against commercial Toraymyxin fibers of the same size. The results demonstrated that the EERD based on the MTAM-A performed superior to that of the commercial equivalent, registering a rapid reduction of 73.18% of endotoxin (vs. Toraymyxin at 38.78%) at time point 15 min and a final total endotoxin removal of 89.43% (vs. Toraymyxin at 65.03%)

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