MECHANICAL BEHAVIOR OF ADHESIVELY-BONDED JOINTS UNDER HIGH LOADING RATES

2021 ◽  
Author(s):  
MEHMET EMIN ERCAN ◽  
FERHAT KADIOGLU
Keyword(s):  
Adhesive Layer ◽  
Experimental Tests ◽  
Lap Joints ◽  
Adhesively Bonded ◽  
Case Scenario ◽  
Worst Case ◽  
Adhesive Film ◽  
Package Program ◽  
Set Up ◽  
Static Conditions

This work aims to investigate the dynamic behavior of adhesively-bonded Single Lap Joints (SLJs) under ballistic conditions. For this purpose, the joints with clamped-clamped boundary conditions were modelled using a Finite Element Method (FEM) via ABAQUS package program. The numerical model is based on the joint subjected to a projectile with a mass of 1.25 gr, a density of 11.3 gr/cm3, and an impacting velocity of 100 m/s. The experimental tests conducted in a specially designed set-up were performed via an air-pressurized gun. 6061 aluminum adherends and an adhesive film were used to manufacture the bonded structure. Curves of the velocity and dynamic load against time were predicted for the joint under the impacting projectile. Failure and stress distributions in the adherend as well as in the adhesive layer were predicted that was validated via the experimental results. The prediction was made according to the worst case scenario that accounts the input data obtained from the quasi-static conditions.

scholarly journals Compression Shear Properties of Adhesively Bonded Single-Lap Joints of C/C Composite Materials at High Temperatures

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1437 ◽  
Author(s):  
Yanfeng Zhang ◽  
Zhengong Zhou ◽  
Zhiyong Tan
Keyword(s):  
Composite Materials ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Experimental Result ◽  
Shear Stresses ◽  
Test Results ◽  
Adhesively Bonded ◽  
Finite Element Software ◽  
Joint Structure ◽  
Simulation Results

The performance of joint structure is an important aspect of composite material design. In this study, we examined the compression shear bearing capacity of the adhesively bonded single-lap joint structure of high-temperature-resistant composite materials (C/C composite materials). The test pieces were produced in accordance with the appropriate ASTM C1292 standard, which were used for the compression shear test. The failure morphology of the layer was observed by a digital microscopic system and scanning electron microscope. The experimental result shows that the load on the test piece increased nonlinearly until the failure occurred, and most of the adhesive layer exhibited cohesive failures at three temperature points (400, 600, and 800 °C), while the interface failures occurred in a small part of the adhesive layer. A numerical analysis model was established using ABAQUS finite element software. The simulation results were compared with the test results to verify the correctness of the model. On the basis of correctness of the model verified by comparing the simulation results and the test results, the influences of temperature and overlapped length on the joint compression shear performance were studied through the validated simulation method. Numerical results showed that the ultimate load of the joint decreased with increases in temperature and that the distribution trends of the shear stresses in the overlapped length direction were substantially the same for joints of different overlapped lengths.

Experimental and Analytical Investigations of the Dynamic Response of Adhesively Bonded Single Lap Joints

2004 ◽  
Vol 126 (1) ◽  
pp. 84-91 ◽  
Author(s):  
A. Vaziri ◽  
H. Nayeb-Hashemi ◽  
H. R. Hamidzadeh
Keyword(s):  
Dynamic Response ◽  
Loss Factor ◽  
Natural Frequencies ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Laser Vibrometer ◽  
Total System ◽  
Adhesive Film ◽  
Single Lap Joints ◽  
Central Void

Dynamic response of single lap joints, subjected to a harmonic peeling load is studied theoretically and experimentally. In the theoretical part, dynamic response of a single lap joint clamped at one end and subjected to a harmonic peeling load at the other end is investigated. Adherents are modeled as Euler-Bernouli beams joined in the lap area by a viscoelastic adhesive layer. Both axial and transverse deformations of adherents are considered in deriving the equations of motion. The effects of adhesive layer thickness, mechanical properties and its loss factor on the dynamic response of the joint are investigated. Furthermore, effects of defects such as a void in the lap area on the dynamic response of the joints are studied. The results showed that frequencies where peak amplitudes occurred were little dependent on the adhesive loss factor. However, peak amplitudes reduced for joints with a higher adhesive loss factor. Furthermore, the results indicated that for the joint geometries and properties investigated the system resonant frequencies were not affected by the presence of a central void covering up to 80% of the overlap length. In the experimental part, single lap joints were fabricated using 6061-T6 Aluminum. Adherents were joined together using Hysol EA 9689 adhesive film. Joints with various central voids were manufactured by removing adhesive film from the desired area of lap joints prior to bonding adherents. Dynamic responses of the joints were investigated using the hammer test technique. The system response was measured using both an accelerometer and a noncontact laser vibrometer. The natural frequencies of the joints obtained by using the laser vibrometer were very close to those obtained theoretically. However, natural frequencies obtained by using an accelerometer depended on the accelerometer location in the system, which was attributed to its mass contribution to the over- all system mass. A central void covering less than 80% of the overlap length had little effect on the system resonance frequencies. This was in agreement with the theoretical results. In contrast total system-damping ratios were a function of the void size. Joints without a void exhibited higher damping.

Simplified stiffness analysis for degraded single lap joints in the space sector – Comparative analytical and finite element analysis

2020 ◽  
Vol 234 (13) ◽  
pp. 1956-1966
Author(s):  
Jannik Zimmermann ◽  
Josef Weiland ◽  
Mohammad Zamaan Sadeghi ◽  
Alexander Schiebahn ◽  
Uwe Reisgen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Ionizing Radiation ◽  
Coefficient Of Thermal Expansion ◽  
Closed Form Solution ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Polymer Chains ◽  
Adhesively Bonded ◽  
European Organization

Considering the aerospace sector, the use of adhesively bonded joints is constantly increasing over the last decades. Due to its lightweight and capability of joining various materials with different coefficient of thermal expansion, this joining technique offers many benefits over conventional methods like rivets, screws and welding. On the other hand, structural adhesives consists of polymer chains that can be severely affected by the environment. An example of such an environmental effect is the interaction of the polymer chains of the adhesive with ionizing radiation in space. Nevertheless in the literature, the influence of ionizing radiation on the mechanical properties of epoxides is covered but not well understood. The present work describes a method of determining the stiffness of an adhesively bonded single lap joint (SLJ) using closed form solution equations. This analytical approach is compared with a numerical model. The mechanical properties of the adhesive in both models is degraded due to irradiation, based on experiments conducted by the European Organization for Nuclear Research (CERN). The results show that the degradation of the mechanical properties of the adhesive layer has a significant influence on the joint stiffness. This effect increases with growing adhesive layer thickness. Comparing the results with a finite element model, it is shown that the developed calculation scheme overestimates the stiffness of the SLJ. This is caused by the neglection of bending stresses within the adherends.

Acoustic Emission on Adhesively Bonded Single-Lap Joints of Composite Laminate during Tensile Test

2014 ◽  
Vol 912-914 ◽  
pp. 441-444
Author(s):  
Yan Rong Pang ◽  
Ran Liu ◽  
Ya Juan Li ◽  
Bo Han Lu ◽  
Xin Kang Xing ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Tensile Test ◽  
Composite Laminate ◽  
Mechanical Response ◽  
Adhesive Layer ◽  
Relative Energy ◽  
Lap Joints ◽  
Adhesively Bonded ◽  
Damage And Failure ◽  
Single Lap Joints

Acoustic emission (AE) was used to monitor the tensile test of composites with adhesive specimens. The mechanical response behavior, damage and failure characteristics, and the corresponding AE characteristics of the composites have been investigated. The results show that the load of the join with defect in the adhesive layer is lower than the join with no defect. The higher AE relative energy and the AE amplitude were obtained in the adhesive specimen with defect in the adhesive layer whereas the variation of the AE relative energy is different from the adhesive specimen with on defect. The characteristics such as AE amplitude distribution, relative energy and cumulative hits are connected with the tensile damage and failure of the adhesively bonded single-lap joints of composite laminate. In the actual AE monitoring, these feature parameters should be considered entirely assess the damage and failure of the composites structures.

A Coupled Peel and Shear Stress-Diffusion Model for Adhesively Bonded Single Lap Joints

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Emad Mazhari ◽  
Sayed A. Nassar
Keyword(s):  
Shear Stress ◽  
Diffusion Model ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Fickian Diffusion ◽  
Lap Joint ◽  
Adhesively Bonded ◽  
Single Lap Joints ◽  
Single Lap Joint ◽  
Stress Diffusion

In this study, the Fickian diffusion formulation is extended to the adhesive layer of a single lap joint (SLJ) model, in order to develop a coupled peel and shear stress-diffusion model. Constitutive equations are formulated for shear and peel stresses in terms of adhesive material properties that are time- and location-dependent. Numerical solution is provided for the effect of diffusion on shear and peel stresses distribution. Detailed discussion of the results is presented.

‘Please make your verdict speak the truth’: Insights from an Appraisal analysis of the closing arguments from a rape trial

2020 ◽  
Vol 40 (4) ◽  
pp. 421-442
Author(s):  
Leanne Victoria Bartley
Keyword(s):  
Common Knowledge ◽  
Case Scenario ◽  
Worst Case ◽  
Non Profit ◽  
Closing Arguments ◽  
Language Choices ◽  
Rape Trial ◽  
Appraisal Analysis ◽  
Set Up ◽  
A Minor

AbstractIt is common knowledge that language use inside the courtroom is an effective tool of persuasion; thus, even in cases where evidence is unreliable, men and women have found themselves facing charges, standing trial and, in the worst case scenario, wrongfully convicted of a crime. In this paper I examine one such case, in which a young American finds himself accused and, later, imprisoned for the rape of a minor, despite evidence to suggest otherwise. The case is taken from a database set up by The Innocence Project, a non-profit organisation comprising a team of volunteers working towards proving the innocence of over 200 individuals currently serving time for a crime that they insist they did not commit. More specifically, my analytical focus is on the closing arguments of the selected case for the purposes of acquiring insights into how the attorneys for each side make particular language choices in a final attempt to maximise the credibility of their version of events. To reveal how the defendant and the victim are portrayed by each of the lawyers and, moreover, whose feelings and/or character traits are brought to the forefront, an Appraisal analysis is carried out on the dataset.

scholarly journals Experimental and Numerical Study of Low-Velocity Impact and Tensile after Impact for CFRP Laminates Single-Lap Joints Adhesively Bonded Structure

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1016
Author(s):  
Chunxing Hu ◽  
Guibin Huang ◽  
Cheng Li
Keyword(s):  
Lap Joints ◽  
Low Velocity Impact ◽  
Adhesively Bonded ◽  
Low Velocity ◽  
Adhesive Film ◽  
Velocity Impact ◽  
Cfrp Laminates ◽  
Single Lap Joints ◽  
Impact Energies ◽  
The Impact

To investigate the mechanical behavior of the single-lap joints (SLJs) adhesively bonded structure of carbon fiber reinforced polymer (CFRP) laminates under the low-velocity impact (LVI) and tensile-after impact (TAI), tests and simulations were carried out. A finite element model (FEM) was established based on the cohesive zone model (CZM) and Hashin criterion to predict the damage evolution process of adhesive film, intra- and inter-laminar of the SLJs of CFRP laminates, and its effectiveness was verified by experiments. Moreover, three different overlap lengths (20 mm, 30 mm, and 40 mm) and four different impact energies (Intact joint, 10 J, 20 J, and 30 J) are considered in the present study. Finally, the effects of different impact energies and overlap lengths on the residual strength of SLJs after impact were discussed. The results divulged that numerical results of impact and TAI processes of SLJs were in good agreement with experiment results. During the impact process, the damage of the laminates was primarily fiber and matrix tensile damage, whereas the adhesive film was damaged cohesively; the areas of damage increased with the increase of impact energy, and the normal stress of the adhesive film expanded from the edge to the middle region with the increase of impact force. The influence of LVI on SLJs adhesively bonded structures was very significant, and it is not effective to obtain a higher impact resistance by increasing the overlap length. For the tensile process, the failure mode of TAI of the SLJs was interface failure, the surplus strength of the SLJs gradually decreased with the increase of the impact energy because of the smaller overlap length, the overlap length more than 30 mm, and the low energy impact has almost no effect on the residual strength of the SLJs.

scholarly journals NHS Nightingale North West: A Medical Student on the Front Lines

2020 ◽  
Author(s):  
Lewis Holt
Keyword(s):  
World Health Organisation ◽  
World Health ◽  
Support Worker ◽  
Case Scenario ◽  
Worst Case ◽  
North West ◽  
The United Kingdom ◽  
Great Insight ◽  
The World ◽  
Set Up

Seemingly overnight, on the 12th of March 2020, healthcare systems the world over changed as the World Health Organisation deemed COVID-19 a worldwide pandemic. I was moved directly into the fourth year of my medical studies without examination, and applied to work in one of the few field hospitals set up across the United Kingdom, designed to handle to worst case scenario of COVID-19. Here I tended to the most basic needs of patients as a care support worker and witness first hand the relentlessness of this awful disease.  Being able to help and work in a role I was not familiar with has given me great insight into the needs of patient’s whether they are going home or in their final days of life.  As the pandemic cools down and the incidence curve flattens, we have all been put on standby, hopefully not to be required again.

A Coupled Shear Stress-Diffusion Model for Adhesively Bonded Single Lap Joints

2016 ◽  
Vol 83 (10) ◽  
Author(s):  
Sayed A. Nassar ◽  
Emad Mazhari
Keyword(s):  
Shear Stress ◽  
Diffusion Model ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Fickian Diffusion ◽  
Equilibrium Equations ◽  
Adhesively Bonded ◽  
Adhesive Material ◽  
Single Lap Joints ◽  
Stress Diffusion

In this study, a coupled shear stress-diffusion model is developed for the analysis of adhesively bonded single lap joints (SLJs) by applying Fickian diffusion model to the adhesive layer. Differential equations of equilibrium are formulated in terms of adhesive material properties that are time and location dependent. By invoking a Volkersen approach on the equilibrium equations, a shear stress differential equation is formulated and numerically solved. Several scenarios are considered for investigating the effect of diffusion on shear stress distribution in adhesively bonded SLJs. Detailed discussion of the results is presented.

Experimental Investigation of Metallic Fiber-Reinforced Adhesively Bonded Joints under Bending

2017 ◽  
Vol 754 ◽  
pp. 252-255
Author(s):  
S.M.J. Razavi ◽  
F. Berto
Keyword(s):  
Adhesive Layer ◽  
Longitudinal Direction ◽  
Lap Joints ◽  
Experimental Investigations ◽  
Adhesively Bonded ◽  
Load Bearing ◽  
Single Lap Joints ◽  
Bonded Joint ◽  
Failure Loads ◽  
Fibers Orientation

In the current paper, the geometric and material parameters of metal fibers utilized for strengthening adhesively bonded single lap joints under flexural loading were investigated by using experimental investigations. According to the test results, incorporating metal fibers in the adhesive layer of a bonded joint can have a significant impact on the flexural load bearing of the joint. The distance between the fibers and also the fibers orientation were considered as the key parameters in this research. It was concluded that the load bearing of the joint can be improved by reducing the distance between the fibers and the highest failure loads were obtained for the joints reinforced by fibers in the longitudinal direction.

Sign in / Sign up

Export Citation Format

Share Document