Strategies for the Analysis of the Behavior of an Adhesive in Bonded Assemblies

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Jean Yves Cognard ◽  
Romain Créac’hcadec ◽  
Laurent Sohier
Keyword(s):  
Experimental Data ◽  
Edge Effects ◽  
Nonlinear Behavior ◽  
Bonded Joints ◽  
Stress Singularities ◽  
Tensile Shear ◽  
Adhesively Bonded ◽  
Shear Tests ◽  
Lap Shear ◽  
Initiation And Propagation

Experimental and numerical analyses of the mechanical behavior of bonded joints can be made particularly difficult by the influence of edge effects. Therefore, understanding the stress distribution in an adhesive joint can lead to improvements in adhesively-bonded assemblies. Such an analysis is proposed in the case of usual single lap shear specimens. Stress singularities can contribute to the initiation and propagation of cracks in the adhesive. Thus, in order to obtain reliable experimental data to analyze the nonlinear behavior of an adhesive in an assembly, tests which strongly limit the influence of stress singularities must be proposed. The design and the abilities of such a device for shear tests are presented. Moreover, some experimental results obtained using a modified Arcan fixture, which has been designed to strongly limit edge effects, are presented in the case of monotonic and complex history loadings. Furthermore, a 2D non associated elasto-visco-plastic model is proposed to accurately describe the experimental behavior under tensile-shear monotonic loadings. An extension of this model is also proposed to represent relaxation type effects under shear loadings.

Effect of aluminium substrate thickness on the lap-shear strength of adhesively bonded and hybrid riveted-bonded joints

2020 ◽  
pp. 095440892091343
Author(s):  
VC Beber ◽  
N Wolter ◽  
B Schneider ◽  
K Koschek
Keyword(s):  
Shear Strength ◽  
Failure Process ◽  
Lap Joints ◽  
Substrate Thickness ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Lap Shear Strength ◽  
Lap Shear ◽  
Definition Of ◽  
Structural Adhesive

For lightweight materials, e.g. aluminium, the definition of proper joining technology relies on material properties, as well as design and manufacturing aspects. Substrate thickness is especially relevant due to its impact on the weight of components. The present work compares the performance of adhesively bonded (AJ) to hybrid riveted-bonded joints (HJ) using aluminium substrates. To assess the lightweight potential of these joining methods, the effect of substrate thickness (2 and 3 mm) on the lap-shear strength (LSS) of single lap joints is investigated. An epoxy-based structural adhesive is employed for bonding, whilst HJs are produced by lockbolt rivet insertion into fully cured adhesive joints. The stiffness of joints increased with an increase of substrate thickness. HJs presented two-staged failure process with an increase in energy absorption and displacement at break. For HJs, the substrate thickness changed the failure mechanism of rivets: with thicker substrates failure occurred due to shear, whereas in thinner substrates due to rivet pulling-through. The LSS of 2 mm and 3 mm-thick AJs is similar. With 2 mm-thick substrates, the LSS of HJs was lower than AJs. In contrast, the highest LSS is obtained by the 3 mm-thick HJs. The highest lightweight potential, i.e. LSS divided by weight, is achieved by the 2 mm-thick AJs, followed by the 3 mm-thick HJs with a loss of ca. 10% of specific LSS.

scholarly journals Numerical evaluation of crack stopping mechanisms in composite bonded joints due to corrugation and bolts

2019 ◽  
Vol 304 ◽  
pp. 01003 ◽  
Author(s):  
Konstantinos Tserpes
Keyword(s):  
Crack Growth ◽  
Cohesive Zone ◽  
Cohesive Zone Modeling ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Static Loads ◽  
Lap Shear ◽  
Crack Growth Simulation ◽  
Zone Modeling ◽  
Fatigue Loads

In this paper, the crack stopping mechanisms in corrugated composite bonded joints and hybrid bonded/bolted joints were evaluated numerically using the cohesive zone modeling approach. For the study, the DCB (double-cantilever beam) and the CLS (crack-lap shear) specimens were modelled. The first two specimens were subjected to static loads and the latter both to static and fatigue loads. The analysis was performed using the LS-DYNA explicit FE code. Fatigue crack growth simulation was performed using an in-house developed user-defined subroutine (UMAT). The numerical results reveal a crack stopping in the corrugated DCB, no crack stopping in the corrugated CLS and a reduction of crack growth rate in the bonded/bolted CLS for both static and fatigue loads. The methods and the findings of the present study can be used for the design of crack stopping features in adhesively bonded primary composite aircraft structures.

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.

Analysis of Adhesively Bonded Joints Between Panels of Composite Materials

1977 ◽  
Vol 44 (1) ◽  
pp. 101-106 ◽  
Author(s):  
W. J. Renton ◽  
J. R. Vinson
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Orthotropic Material ◽  
Structural Response ◽  
Lap Joints ◽  
Bonded Joints ◽  
Excellent Correlation ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Material Systems

A mathematical model is developed and methods of analysis are formulated for determining the structural response of the single-lap and symmetric-lap joints composed of generally orthotropic material systems. Analytical results are compared in both instances with experimental data and excellent correlation is seen to exist.

scholarly journals An experimental investigation on the effect of adhesive distribution on strength of bonded joints

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
A. P. Pisharody ◽  
B. Blandford ◽  
D. E. Smith ◽  
D. A. Jack
Keyword(s):  
Joint Strength ◽  
Adhesive Joints ◽  
Bonded Joints ◽  
Shear Tests ◽  
Lap Shear ◽  
Loading Direction ◽  
Distribution Shape ◽  
Adhesive Application ◽  
Pulse Echo ◽  
Overlap Area

AbstractAdhesive joints are widely used due to their higher strengths, lower weights, lesser expenses and ease of fabrication than other methods of joining. Hence, they are used extensively in aerospace and automobile industries. High quality bonds require the use of fixtures which are essential to ensure proper curing and to attain uniform thickness. Improper adhesive application and method of fixturing can cause irregularities in the distribution of the adhesive along the overlap which could affect the joint strength. This is especially critical for aerospace components as the replacement of parts can be costly and time consuming. This paper presents a nondestructive test (NDT) methodology to quantify the bonded joints where the adhesive does not completely cover the overlap area. Single lap adhesive joints with carbon fiber adherents were fabricated using a two-part epoxy based adhesive. The adhesive region was fabricated to have various shapes including elliptical and circular of different sizes and a joint with full coverage for comparison. Polytetrafluoroethylene (PTFE) cutouts were used to mask regions of adhesive to achieve the desired coverage pattern. After fabrication all samples were ultrasonically scanned with a 10 MHz spherically focused immersion transducer using pulse-echo ultrasonics to determine the actual as tested adhesive distribution shape. The scans were able to resolve the shape of adhesive distribution across the overlap region of 25.4 × 25.4 mm and were correlated with the actual adhesive distribution at the interface after lap shear tests. Lap shear tests were then performed on the samples fabricated and the samples were loaded to failure. It was found that the shape and the orientation of the adhesive shape relative to the loading direction had an effect on failure strength.

Nondestructive Evaluation of Adhesively Bonded Joints in Graphite/Epoxy Composites Using Acousto-Ultrasonics

1992 ◽  
Vol 114 (3) ◽  
pp. 344-352 ◽  
Author(s):  
S. Tanary ◽  
Y. M. Haddad ◽  
A. Fahr ◽  
S. Lee
Keyword(s):  
Mechanical Performance ◽  
Bonded Joints ◽  
Propagation Characteristics ◽  
Lap Joint ◽  
Adhesively Bonded ◽  
Shear Tests ◽  
Adhesively Bonded Joints ◽  
Testing Conditions ◽  
Single Lap Joint ◽  
Film Adhesive

This paper is concerned with the use of the acousto-ultrasonic technique to evaluate nondestructively the mechanical performance of composite bonded joints. In this context, acousto-ultrasonic measurements followed by destructive shear tests were performed on single lap joint specimens made from graphite/epoxy adherends joined with FM 300 film adhesive. The results indicate a good correlation between acousto-ultransonic wave propagation characteristics and the shear strength of the bonded joints under different testing conditions. These correlations suggest that an estimation of the joint strength can be made by using acousto-ultrasonics provided that the measurement system is calibrated for variations of the material and geometry of the specimen.

Experimental Investigation on Effective Bond Length of Flexurally CFRP-Strengthened RC Beams Failed by Intermediate Crack Debonding

2010 ◽  
Vol 163-167 ◽  
pp. 977-980
Author(s):  
Gui Bing Li ◽  
Ai Hui Zhang ◽  
Wei Liang Jin
Keyword(s):  
Experimental Data ◽  
Bond Length ◽  
Shear Test ◽  
Plastic Hinge ◽  
Experimental Results ◽  
Rc Beams ◽  
Shear Tests ◽  
Lap Shear ◽  
Test Models ◽  
Plastic Hinge Length

The models to calculate the effective bond length determined by single-lap or double-lap shear tests are more suitable for the end-debonding failure; and the improved models based on the simply shear test models to calculate the effective bond length of flexural CFRP-strengthened beams failed by intermediate crack debonding (IC debonding) are also lack of the support of experimental data. To investigate the effective bond length of flexural CFRP-strengthened beams, a total of 9 flexurally CFRP-strengthened beams were tested. The experimental results show that the existing models are very conservative for calculating the effective bond length in flexural FRP-strengthened RC beams failed by IC debonding. Based on the experimental results, this paper presents a model to calculate the effective bond length of flexural FRP-strengthened RC beams failed by IC debonding, and a model to calculate the plastic hinge length at the shear-flexure span.

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