Experimental Assessment of the Dynamic Behavior of Polyolefin Thermoplastic Hot Melt Adhesive

2018 ◽  
Author(s):  
Raffaele Ciardiello ◽  
Andrea Tridello ◽  
Luca Goglio ◽  
Giovanni Belingardi
Keyword(s):  
Failure Modes ◽  
Industrial Applications ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Dynamic Tests ◽  
Cohesive Failure ◽  
Static Tests ◽  
Piping Systems ◽  
The Many ◽  
Hot Melt

In the last decades, the use of adhesives has rapidly increased in many industrial fields. Adhesive joints are often preferred to traditional fasteners due to the many advantages that they offer. For instance, adhesive joints show a better stress distribution compared to the traditional fasteners and high mechanical properties under different loading conditions. Furthermore, they are usually preferred for joining components made of different materials. A wide variety of adhesives is currently available: thermoset adhesives are generally employed for structural joints but recently there has been a significant increment in the use of thermoplastic adhesives, in particular of the hot-melt adhesives (HMAs). HMAs permit to bond a large number of materials, including metal and plastics (e.g., polypropylene, PP), which can be hardly bonded with traditional adhesives. Furthermore, HMAs are characterized by a short open time and, therefore, permit for a quick and easy assembly process since they can be easily spread on the adherend surfaces by means of a hot-melt gun and they offer the opportunity of an ease disassembling process for repair and recycle. For all these reasons, HMAs are employed in many industrial applications and are currently used also for bonding polypropylene and polyolefin piping systems. In the present paper, the dynamic response of single lap joints (SLJ) obtained by bonding together with a polyolefin HMA two polypropylene substrates was experimentally assessed. Quasi-static tests and dynamic tests were carried out to investigate the strain rate effect: dynamic tests were carried out with a modified instrumented impact pendulum. Relevant changes in the joint performance have been put in evidence. Failure modes were finally analysed and compared. A change in the failure mode is experimentally found: in quasi-static tests SLJ failed due to a cohesive failure of the adhesive, whereas in dynamic tests the SLJ failed due to an interfacial failure, with a low energy absorption.

Experimental and numerical analysis of dual-adhesive stepped-lap aluminum joints

2020 ◽  
Vol 234 (5) ◽  
pp. 454-464
Author(s):  
CL Ferreira ◽  
RDSG Campilho ◽  
RDF Moreira
Keyword(s):  
Cohesive Zone ◽  
Failure Modes ◽  
Cohesive Zone Model ◽  
Stress Gradient ◽  
Maximum Load ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Zone Model ◽  
Behavior Prediction ◽  
Adhesive Bonds

The use of adhesive bonds has attracted considerable interest from the scientific community. Stepped-lap joints have the advantage of decreasing stress gradients along the bond length, although the outer steps still encounter stress levels above the steps in the inner zone of the joint. One possible way to reduce this stress gradient is to combine this type of joint with the use of two adhesives. This work consists of an experimental and numerical evaluation of stepped-lap dual-adhesive joints between aluminum adherends, for various overlap lengths ( LO), and comparison with stepped-lap single-adhesive joints. The adhesives Araldite® AV138, Araldite® 2015, and Sikaforce® 7752 were evaluated. Numerically, cohesive zone models with a triangular damage law were applied in the joint behavior prediction. The analysis of the results is presented in the form of failure modes, stress analysis, damage variable analysis, load–displacement ( P–δ) curves and maximum load ( Pm), and energy required to failure ( U). It was concluded that, in general, cohesive zone model presented precise predictions. In general, no significant increase in strength was achieved with dual-adhesive joint but, on the other hand, significant energy increases were obtained.

Analysis and Characterization of Adhesively Bonded Mg-Steel Lap Joints

2004 ◽  
Author(s):  
Niat M. Rahman ◽  
Ahsan Mian ◽  
Golam M. Newaz
Keyword(s):  
Stress Distribution ◽  
Failure Modes ◽  
Lap Joints ◽  
Computational Method ◽  
Substrate Thickness ◽  
Cohesive Failure ◽  
Adhesively Bonded ◽  
Lap Shear ◽  
Out Of Plane

Dissimilar material joints are of significant interest in automotive applications. An investigation was carried out to determine the peculiarities of an adhesively bonded Mg-steel system for lap shear configuration. Both experimental approach and computational method (FEA) were utilized to evaluate and analyze the Mg-steel bond. The adhesive used was Betamate 1480 — an epoxy based adhesive. The tests were done according to ASTM D 1002-99 method using MTS machine at room temperature. For computational analysis, finite element modeling techniques using ABAQUS processor was utilized. Failure modes were studied for different systems. Results were compared with Mg-Mg and steel-steel systems. It is observed that Mg-Mg balanced system (system with equal adherend or substrate thickness) failed either at interface (adhesive failure) or at substrate and system is flexible with lower failure load. While steel- -steel balanced system failed only at substrate and system is rigid with higher load and lower displacement. Mg-steel system provides flexibility in between them and only adherend failure (either out of plane Magnesium failure or steel-betamate in plane substrate failure) observed. Cohesive failure was not observed in any of the systems. For Mg-Mg, the shear stress distribution in the adhesive is poor (stress distribution is steeper) while for steel-betamate-steel it is much better. The FEA models were compared and rationale was forwarded to assess the failure modes observed in each case.

Experimental Investigation on Adhesive Bonded Joints of Carbon Fiber Composite Laminates Containing Disbond Defect

2017 ◽  
Author(s):  
Ping Qiu ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Carbon Fiber ◽  
Adhesive Bonding ◽  
Phased Array ◽  
Failure Modes ◽  
Fiber Composite ◽  
Failure Process ◽  
Tensile Load ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Image Correlation

Adhesive bonding technology is widely used for connecting composite pipes recent years, for the adhesive joints have many advantages such as weight reduction, ease of manufacture, and more importantly, uniform stress distribution and less stress concentration within the joint region. Nevertheless, one of the limitations of adhesive joints is the difficulty in predicting the joint strength due to the presence of defects in the adhesive due to improper curing process. This paper presents an experimental study of single-lap joints with disbond defects at the adherend-adhesive interface. Different sets of adhesively-bonded singlelap joints containing varied disbond conditions were prepared and tested. The joints used carbon fiber reinforced polymer (CFRP) laminates as substrates and epoxy resin as adhesive, with ultrathin aluminum foil (10um) as disbond defects in different sizes and locations. The full deformation fields were measured using the digital image correlation (DIC) method. The samples were subjected to tensile load till failure to determine the bond strength. Before the tensile test, the defective adhesive joints were detected by a phased-array ultrasonic instrument to identify the bond-line quality of joints. The results show that the disbond defects can be detect by ultrasonic phased-array technique, and the detriment of disbond defect to the failure process can be observed and recorded by DIC system. Based on the findings, the failure modes and failure mechanism of bonded CFRP joint were further discussed.

A robotic chewing simulator supplying six-axis mandibular motion, high occlusal force, and a saliva environment for denture tests

2021 ◽  
pp. 095441192110056
Author(s):  
Wenlong Qin ◽  
Ming Cong ◽  
Dong Liu ◽  
Xiang Ren
Keyword(s):  
Flow Rate ◽  
Failure Modes ◽  
Testing Machine ◽  
Dynamic Test ◽  
Dynamic Tests ◽  
Occlusal Force ◽  
Static Tests ◽  
Static Test ◽  
Axis Parallel

Six-axis motion is essential for the evaluation of the wear failure modes of dental prostheses with complete teeth morphologies, and a high occlusal force capacity is vital for static clenching and dynamic bruxism. Additionally, the saliva environment influences abrasive particles and crack growth. The present research was aimed at the development of a six-axis masticatory and saliva simulator with these capacities. The masticatory simulator was designed based on a six-axis parallel mechanism, and the saliva simulator consisted of a saliva circuit and a temperature control loop. A control system of the masticatory and saliva simulators was constructed. The operating interface includes a centric occlusal position search, a static test, a dynamic test, a saliva supply, and data reporting. The motion and force performances of the masticatory simulator were evaluated. The flow rate and temperature change of the saliva simulator were calculated. For the occlusal position-searching, the driving amplitude is linear with the moving variables during minor one-axis motion. For the static tests, the force capacity of the driving chain is 3540 N, while for the dynamic tests, the force capacity is 1390 N. The flow rate of the saliva is 0.18–51.84 mL/min, and the saliva can effectively wet the prosthesis without the risk of overflow. Moreover, the saliva temperature can increase from room temperature (23°C) to body temperature (37°C) in about 6 min. The proposed DUT-2 simulator with six-axis motion, high force, and a salvia environment provides an in vitro testing approach to validate numerical simulation results and explain the clinical failure modes of prostheses. The centric occlusal position-searching, static tests, and dynamic tests could therefore be executed using a single testing machine. Moreover, the proposed device is more compact than previously reported six-axis masticatory simulators, including the Bristol simulator and DUT-1 simulator.

scholarly journals Effect of Holes in Overlap on the Load Capacity of the Single-Lap Adhesive Joints Made of EN AW-2024-T3 Aluminium Alloy

2021 ◽  
Vol 21 (4) ◽  
pp. 112-121
Author(s):  
Władysław Zielecki ◽  
Katarzyna Burnat ◽  
Andrzej Kubit ◽  
Tomáš Katrňák
Keyword(s):  
Load Capacity ◽  
Epoxy Adhesive ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Front Part ◽  
Tensile Shear ◽  
Static Tests ◽  
Structural Modifications ◽  
Structural Adhesive ◽  
Strength Of Adhesive Joints

Abstract The paper presents the results of experimental research aimed at determining the possibilities of strengthening structural adhesive joints. Techniques to improve the strength of adhesive joints was to make holes in the front part of the adherends in order to make the joint locally more flexible in the area of stress concentration at the joint edges. The tests were carried out for the lap joints of EN AW-2024-T3 aluminum alloy sheets, which were bonded with Loctite EA3430 epoxy adhesive. Static tests were carried out on the basis of the tensile/shear test. It has been shown that the applied structural modifications allow for an increase in the strength of the joint, in the best variant, an increase in strength of 14.5% was obtained. In addition, it has been shown that making holes in the adherends allows to reduce the spread of strength results.

BOND STRENGTH DEGRADATION OF ADHESIVE- BONDED CFRP COMPOSITE LAP JOINTS AFTER LIGHTNING STRIKE

2021 ◽  
Author(s):  
WENHUA LIN ◽  
YEQING WANG ◽  
SPENCER LAMPKIN ◽  
SRIHARI GANESH PRASAD ◽  
OLESYA ZHUPANSKA ◽  
...  
Keyword(s):  
Bond Strength ◽  
Failure Modes ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Current Work ◽  
Lightning Strike ◽  
Adhesively Bonded ◽  
Shear Tests ◽  
Lap Shear ◽  
Lightning Current

Adhesive bonding to join fiber reinforced polymer matrix composites holds great promise to replace conventional mechanical attachment techniques for joining composite components. Understanding the behavior of these adhesive joints when subjected to various environmental loads, such as lightning strike, represents an important concern in the safe design of adhesively bonded composite aircraft and spacecraft structures. In the current work, simulated lightning strike tests are performed at four elevated discharge impulse current levels (71.4, 100.2, 141, and 217.8 kA) to evaluate the effects of lightning strike on the mechanical behavior of single lap joints. After documentation of the visually observed lightning strike induced damage, single lap shear tests are conducted to determine the residual bond strength. Post-test visual observation and cross-sectional microscopy are conducted to document the failure modes of the adhesive region. Although the current work was performed on a limited number of specimens, it identified important trends and directions for future more comprehensive studies on lightning strike effects in adhesively bonded composites. It is found that the lightning strike induced damage (extent of the surface vaporization area and the delamination depth) increases as the lightning current increases. The stiffness of the adhesive joints and shear bond strength did not show a clear correlation with the lightning current levels, which could be due to many competing factors, including the temperature rise caused by the lightning strike and the surface conditions of the adherends prior to bonding. The failure modes of the adhesive regions for all specimens demonstrate a mixed mode of adhesive and cohesive failure, which may be due to inconsistent surface characteristics of the adherends before bonding. The energy absorbed during the lap shear tests generally increases as the lightning current increases.

scholarly journals Optimization of Joint Strength of Adhesively Bonded Glass Fiber Epoxy Based Double Strap Butt Joint

2019 ◽  
Vol 8 (6) ◽  
pp. 5022-5025
Keyword(s):  
Glass Fiber ◽  
Composite Laminates ◽  
Joint Strength ◽  
Failure Modes ◽  
Adhesive Layer ◽  
Industrial Applications ◽  
Butt Joint ◽  
Fiber Reinforced ◽  
Cohesive Failure ◽  
Adhesively Bonded

Fiber reinforced composite laminates has various industrial applications. It is important to investigate the joining methods of composite laminates. In this research paper, the effect of overlap length (OL), surface roughness (SR) and adhesive layer thickness (ALT) on the strength and failure modes of adhesively bonded double strap GFRP (glass fiber reinforced epoxy based composite laminate) butt joint was investigated. The adhesively bonded double strap GFRP butt joints were prepared from unidirectional glass fiber and epoxy by hand layup technique as per ASTM standard. The number of experiments was optimised using Taguchi’s L9 approach. It is observed that the variation in overlap length has significant effect on butt joint strength. It is also observed that SR and ALT are less significant factors in comparison to OL. It is concluded that increase in ALT adversely affect the butt joint strength. The failure mode in specimens was generally thin layer cohesive failure or light fiber tear failure.

The Behaviour Of Square Sandwich Panel Part I: Under Static Loading

2012 ◽  
Author(s):  
Amran Alias ◽  
Nor Azlan Ahmad Nor ◽  
Mohd Radzai Said
Keyword(s):  
Static Loading ◽  
Sandwich Panel ◽  
Failure Modes ◽  
Dynamic Tests ◽  
Concentrated Load ◽  
Static Tests ◽  
Static Test ◽  
Pu Foam ◽  
Materials Used ◽  
Observed Damage

Kajian mengenai panel apit segi empat terdiri daripada dua bahagian. Dalam bahagian pertama, prestasi dan kelakuan panel apit segi empat yang dikenakan beban statik dikaji. Panel apit ini sokong oleh unit sokongan dan dikenakan bebanan dibahagian tengahnya dengan menggunakan penakuk separa bulat dan penakuk rata. Panel apit spesifik yang digunakan untuk projek ini ialah kepingan keluli lembut, foam PVC yang dinamakan R55 dan teras daripada busa poli uretana (PU). Tujuan kajian ini adalah untuk mendapatkan bukti secara eksperimen tentang corak serta jenis kegagalan panel apit segi empat yang dikenakan beban tumpu di tengah–tengahnya dan disokong pada setiap bucunya. Selepas ujian statik dilakukan, lengkungan bagi setiap panel ditentukan. Hubungan antara pertumbuhan kerosakan dan kelakuan kerosakan semasa ujian statik ke atas panel dikaji. Dalam bahagian kedua, ujian dinamik dijalankan untuk menentukan prestasi, kelakuan, dan kesan bagi jenis busa serta hubungan antara tenaga masukan daripada ujian statik dan dinamik. Kata kunci: Panel apit segi empat, foam PU, foam PVC (R55), mod kegagalan This series of papers on behaviour of square sandwich panel consists of two parts. In part I, the performance and behaviour of the square sandwich panel under static loading was first examined. The sandwich panel was centrally loaded by using hemispherical and flat indenters on their respective support units. The panel materials used specifically for this project are mild steel skin and PVC foam namely R55 and polyurethane (PU) foam cores. The aim of this study is to obtain experimental evidence of the failure modes of square sandwich panels under concentrated load at the centre of panels, simply supported at the four edge corners for the square panel. After static tests, the whole curves for each panel were determined. The relation between the observed damage evelopment, the property of degradation during the static test of the panels was investigated. In part II, the dynamic tests will be conducted in order to determine the performance, behaviour, effect of foam’s type and the correlation between input energy from static and dynamic tests. Key words: Square sandwich panel, PU foam, PVC foam (R55), failure modes

A Novel Micro Capacitance Sensor for Studying Hydrodynamics of Particle Laden Flow

2000 ◽  
Author(s):  
Z. Pokusevski ◽  
I. G. Evans ◽  
T. A. York ◽  
T. Dyakowski
Keyword(s):  
Industrial Applications ◽  
Dynamic Tests ◽  
Capacitance Sensor ◽  
Particle Detection ◽  
Cfd Simulations ◽  
Static Tests ◽  
Dispersed Particles ◽  
Wide Range ◽  
Particle Laden Flow ◽  
Good Agreement

Abstract Particle laden flows occur in a wide range of industrial applications. Detection of dispersed particles and drops is of enormous importance since they may cause “erosion-corrosion effects” in industrial equipment. This paper presents a novel technique for particle detection. The results show 20 and 50 micron particles detected in the static tests. CFD simulations were carried out in order to design the sensor mounting and its optimal inclination to the flow. It was shown that sensor inclination of 5 or 10 degrees to the flow is highly beneficial. Dynamic tests were carried out and the full results show good agreement with the predicted particle tracks. 50 and 20 micron polyamide particles were detected at air velocities up to 12 metres per second.

scholarly journals Effect of Service Temperature on Mechanical Properties of Adhesive Joints after Hygrothermal Aging

Polymers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3741
Author(s):  
Wei Tan ◽  
Jingxin Na ◽  
Zhaofeng Zhou
Keyword(s):  
Mechanical Properties ◽  
Normal Stress ◽  
Failure Modes ◽  
Failure Load ◽  
Adhesive Joints ◽  
Service Temperature ◽  
Polyurethane Adhesive ◽  
Interface Failure ◽  
Static Tests ◽  
Hygrothermal Aging

Polyurethane adhesive and aluminum alloy were selected to make adhesive joints. Butt joints tested at different loading angles (0°, 45°, and 90°) using a modified Arcan fixture were selected to represent three stress states (normal stress, normal/shear combined stress, and shear stress, respectively). Firstly, the accelerated aging tests were carried out on the joints in a hygrothermal environment (80 °C/95% RH). The quasi-static tests were carried out at different temperatures (−40 °C, 20 °C, and 80 °C) for the joints after hygrothermal aging for different periods. The variation rules of the joints’ mechanical properties and failure modes with different aging levels were studied. The results show that the failure load of the joints was obviously affected by stress state and temperature. In the low-temperature test, the failure load of the joints decreased most obviously, and the BJ was the most sensitive to temperature, indicating that the failure load decreased more with the increase of the normal stress ratio in the joint. Through macroscopic and SEM analysis of the failure section, it was found that the hydrolysis reaction of polyurethane adhesive itself and the interface failure of the joints were the main reasons for the decrease of joint strength. The failure models were established to characterize the adhesive structure with different aging levels at service temperature.

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