Mechanical behaviour of adhesively bonded composite single lap joints under quasi-static and impact conditions with variation of temperature and overlap

2018 ◽  
Vol 52 (26) ◽  
pp. 3621-3635 ◽  
Author(s):  
JJM Machado ◽  
EAS Marques ◽  
LFM da Silva
Keyword(s):  
Automotive Industry ◽  
Full Range ◽  
Testing Temperature ◽  
Unidirectional Composite ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Impact Loads ◽  
Adhesively Bonded ◽  
Impact Performance ◽  
Rate Dependent

The use of adhesively bonded joints in structural components for the automotive industry has significantly increased over the last years, supported by the widespread integration of composite materials. This synergy allows vehicle manufacturers to offer a significant weight reduction of the vehicle allowing for fuel and emissions reduction and, at the same time, providing high mechanical strength. However, to ensure vehicle safety, the crashworthiness of these adhesive joints must be assessed, to evaluate if the structures can sustain large impact loads, transmitting the load and absorbing the energy, without damaging the joint. The novelty of this work is the study of the strain rate dependent behaviour of unidirectional composite adhesive joints bonded with a ductile epoxy crash resistant adhesive, subjected to low and high testing temperatures and using different overlap lengths. It was demonstrated that joints manufactured with this type of adhesive and composite substrates can exhibit excellent quasi-static and impact performance for the full range of temperatures tested. Increasing the overlap length, and independently of the testing temperature, it was observed an increase of energy absorbed for both quasi-static and impact loads, this is of considerable importance for the automotive industry, demonstrating that composite joints exhibit higher performance under impact.

Experimental analysis of adhesively bonded joints in synthetic- and natural fibre-reinforced polymer composites

2019 ◽  
Vol 54 (9) ◽  
pp. 1245-1255 ◽  
Author(s):  
HFM de Queiroz ◽  
MD Banea ◽  
DKK Cavalcanti
Keyword(s):  
Polymer Composites ◽  
Automotive Industry ◽  
Natural Fibre ◽  
Lap Joints ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Reinforced Polymer ◽  
Fibre Composites ◽  
Fibre Reinforced Polymer

The application of adhesively bonded joints in automotive industry has increased significantly in recent years mainly because of the potential for lighter weight vehicles, fuel savings and reduced emissions. The use of composites in making automotive body components to achieve a reduced vehicle mass has also continuously increased. Natural fibre composites have recently attracted a great deal of attention by the automotive industry due to their many attractive benefits (e.g. high strength-to-weight ratio, sustainable characteristics and low cost). However, the literature on natural fibre-reinforced polymer composite adhesive joints is scarce and needs further investigation. The main objective of this study was to evaluate and compare the mechanical performance of adhesively bonded joints made of synthetic- and natural fibre-reinforced polymer composites. Similar and dissimilar single lap joints bonded with a modern tough structural adhesive used in the automotive industry, as well as the epoxy resin AR260 (the same resin used in composite fabrication) were tested. It was found that the average failure loads varied significantly with adhesive material strength and adherend stiffness. Furthermore, it was also observed that failure mode has a significant effect in failure load. The jute-based natural fibre composites joints, both hybrid and purely natural, were superior in strength compared to the sisal-based natural composites joints.

Effect of Impact-Fatigue on Damage in Adhesive Joints

2007 ◽  
Vol 347 ◽  
pp. 653-658 ◽  
Author(s):  
Juan Pablo Casas-Rodriguez ◽  
Ian A. Ashcroft ◽  
Vadim V. Silberschmidt
Keyword(s):  
Damage Evolution ◽  
Weight Ratio ◽  
High Strength ◽  
Fatigue Loading ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Bonded Joints ◽  
Impact Fatigue ◽  
Adhesively Bonded ◽  
Low Velocity

In recent decades the use of structural adhesive joints in the aerospace industry has increased considerably thanks to their high strength-to-weight ratio, low stress concentration and capacity to join different adherends. There is increasing interest in damage due to low-velocity impacts produced in adhesively bonded components and structures by vibrating loads. This type of loading is known as impact fatigue. The main aim of this paper is to investigate damage evolution in adhesive joints subjected to impact-fatigue and to compare this with damage evolution in standard fatigue (i.e. non-impacting, constant amplitude, sinusoidal fatigue). In this work, adhesively bonded lap joints were subjected to multiple tensile impacts tensile and it was seen that this type of loading was extremely damaging compared to standard fatigue. A number of methods of studying damage evolution in bonded joints subjected to fatigue and impact fatigue loading have been investigated and various parameters have been used to characterise these processes. Two modifications of the accumulated time-stress model [1-4] are proposed and it is shown that both models provide a suitable characterization of impact-fatigue in bonded joints.

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.

The Effects of Inherent Flaws on the Time and Rate Dependent Failure of Adhesively Bonded Joints

1982 ◽  
Vol 104 (3) ◽  
pp. 643-650 ◽  
Author(s):  
E. Sancaktar ◽  
S. Padgilwar
Keyword(s):  
Lap Joints ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Concentration Effects ◽  
Adhesively Bonded Joints ◽  
Single Lap Joints ◽  
Creep Stress ◽  
Rate Dependent ◽  
Dependent Failure ◽  
Creep Loading

Experiments on single lap joints bonded with viscoelastic adhesives reveal that the effects of rate and time and inherent flaws are as critical in joint failure as are the environmental and stress concentration effects. Experimental data reveal that random inherent flaws and loading rate changes may result in as much as 40 percent reduction in joint strength. Furthermore when creep loading is used, the asymptotic creep stress, below which no delayed failure will occur, may have to be as much as 45 percent less than the adhesive maximum strength.

EFFECTS OF TEMPERATURE AND FORMING SPEED ON PLASTIC BENDING OF ADHESIVELY BONDED SHEET METALS

2008 ◽  
Vol 22 (31n32) ◽  
pp. 6253-6258 ◽  
Author(s):  
MICHIHIRO TAKIGUCHI ◽  
TETSUYA YOSHIDA ◽  
FUSAHITO YOSHIDA
Keyword(s):  
High Speed ◽  
Lap Joints ◽  
Sheet Metals ◽  
Adhesively Bonded ◽  
Plastic Bending ◽  
Single Lap Joints ◽  
Rate Dependent ◽  
Lap Shear ◽  
High Speed Forming ◽  
Lower Temperature

This paper deals with the temperature and rate-dependent elasto-viscoplasticity behaviour of a highly ductile acrylic adhesive and its effect on plastic bending of adhesively bonded sheet metals. Tensile lap shear tests of aluminium single-lap joints were performed at various temperature of 10-40°C at several tensile speeds. Based on the experimental results, a new constitutive model of temperature and rate-dependent elasto-viscoplasticity of the adhesive is presented. From V-bending experiments and the corresponding numerical simulation, it was found that the gull-wing bend is suppressed by high-speed forming at a lower temperature.

Fatigue Analysis of Adhesively Bonded Single Lap Joints Under Vibration Loads

2012 ◽  
Author(s):  
Weidong Li ◽  
Kunyue Wu ◽  
Yu Du ◽  
Jian Pang ◽  
Ping Hu
Keyword(s):  
Shear Strength ◽  
Fatigue Damage ◽  
Structural Damage ◽  
Fatigue Analysis ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Adhesively Bonded ◽  
Structural Applications ◽  
Vibration Fatigue ◽  
Vibration Loads

Many structural applications of adhesive joints experience vibration loads. The dynamic loads due to vibration motions are therefore one of the primary causes for structural damage, especially when the outside cyclic stir vibration frequency is adjacent to the natural frequencies of the adhesive joint frame. This is so called the vibration fatigue. In this paper, the fatigue behavior of adhesively bonded single lap joint (SLP) subject mainly to normal stresses induced by vibration excitations is investigated. Combining with static tests, the NI PXI-1045 vibration measurement and analysis system are used to analyze the effect of vibration loading on the fundamental modal frequency with long-term fatigue cycle. Furthermore, a virtual fatigue analysis approach for the fatigue damage prediction of adhesive joints subject to vibration loads is performed in this study. It is found that the joint stiffness decreases with the cyclic durations under which the vibration loads are applied. As a result, a stable decrease of the fundamental resonance frequency of the joint structure is observed during the tests. The experimental data demonstrate a significant correlation between the shear strength of adhesive joints and the vibration cycling time. A gradual decrease in the shear strength with increasing load cycles is seen in vibration fatigue, the maximum shear strength of adhesively bonded joints drops about 12% after 1.35e8 cycles. Based on the test data, a new approach called virtual fatigue analysis modeling (VFAM) is proposed for the fatigue damage of the adhesive joints under vibration loads. The VFAM shows that the fatigue damage occurs first at the end of the overlap area of the adhesive layer.

Functionally graded adhesive joints under impact loads

2021 ◽  
pp. 095440702110045
Author(s):  
Mateus dos Reis ◽  
Ricardo Carbas ◽  
Eduardo Marques ◽  
Lucas da Silva
Keyword(s):  
Stress Distribution ◽  
Experimental Testing ◽  
Dissimilar Materials ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Functionally Graded ◽  
Impact Loads ◽  
Stress Concentrations ◽  
The Impact

The industrial application of adhesively bonded joints has increased significantly in the last few years, driven by benefits such as the increased design flexibility, high vibration damping, the capability of joining dissimilar materials and the possibility of being used in combination with other joining techniques. However, the presence of stress concentrations at the overlap ends, especially in single lap joints, is one of the major issues associated with this technique, reducing joint strength. To solve this drawback, several techniques have been proposed, such as the use of adhesive spew, adhesive and adherend shaping, mixed adhesive joints and functionally graded adhesive joints. Functionally graded adhesive joints use an adhesive layer where the properties gradually change along the bondline, which results in the reduction of stress concentration peaks at the ends of the overlap, leading to a more uniform stress distribution. Multiple techniques for the creation of a functionally graded bondline have been presented in the literature, such as the inclusion of particles and nanoparticles and the use of functionally graded curing. However, the experimental works available in the literature only report results for quasi-static loading conditions, with the impact behaviour of these joints being an unstudied topic. The main objective of the present work is to fill this gap and study the mechanical behaviour of functionally graded adhesive joints loaded under impact conditions, using both experimental testing and numerical modelling. The results obtained show that, unlike what is found for quasi-static loads, graded joints do not offer significant strength improvement under impact loads. In contrast, energy absorption is significantly increased. This behaviour is explained by the completely different stress distribution on the adhesive layer for quasi-static and impact conditions, leading to the lower effectiveness of functionally graded adhesive joints under impact loads.

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