A New Finite Fracture Mechanics Approach for Assessing the Strength of Bonded Lap Joints

For the widespread use of adhesive joints an exact and reliable prediction of the strength is mandatory. In this work, a new approach to assess the strength of single lap joints is presented. The approach is based on the hybrid criterion as postulated by Leguillon in the framework of finite fracture mechanics. It strictly combines a consideration of an energy release balance and a fulfillment of a strength criterion. The present work is based on a simple model of the joint behavior and assumptions about crack initiation. From the stress distribution of the classical shear lag theory an incremental energy release rate is derived and is used to formulate the optimization problem of the failure load. The resulting predictions of critical failure loads are compared to experimental results of single lap joints. It is shown that the new approach is able to physically describe crack formation and the corresponding critical load within the framework and limitations of the underlying assumptions and simplifications. The work closes with a discussion of the limitations and an outlook on possible improvements of the underlying models and assumptions.

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Failure analysis of simple overlap bonding joints and numerical investigation of the adhered tip geometry effect on the joint strength

Materials Testing ◽

10.1515/mt-2021-0035 ◽

2021 ◽

Vol 63 (11) ◽

pp. 1007-1011

Author(s):

İsmail Saraç

Keyword(s):

Finite Element Analysis ◽

Experimental Study ◽

Finite Element ◽

Reference Model ◽

Lap Joints ◽

Shear Stresses ◽

Element Analysis ◽

Single Lap Joints ◽

Failure Loads ◽

Previous Experimental Study

Abstract This study was carried out in two stages. In the first step, a numerical study was performed to verify the previous experimental study. In accordance with the previous experimental study data, single lap joints models were created using the ANSYS finite element analysis program. Then, nonlinear stress and failure analyses were performed by applying the failure loads obtained in the experimental study. The maximum stress theory was used to find finite element failure loads of the single lap joints models. As a result of the finite element analysis, an approximate 80 % agreement was found between experimental and numerical results. In the second step of the study, in order to increase the bond strength, different overlap end geometry models were produced and peel and shear stresses in the adhesive layer were compared according to the reference model. As a result of the analyses, significant strength increases were calculated according to the reference model. The strength increase in model 3 and model 5 was found to be 80 % and 67 %, respectively, relative to the reference model.

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Verification of Selected Failure Criteria for Adhesive Bonded Elements with Different Stiffness through the Use of Methacrylic Adhesive

Materials ◽

10.3390/ma13184011 ◽

2020 ◽

Vol 13 (18) ◽

pp. 4011

Author(s):

Paweł Maćkowiak ◽

Bogdan Ligaj ◽

Dominika Płaczek ◽

Maciej Kotyk

Keyword(s):

Strength Criterion ◽

Failure Criteria ◽

Lap Joints ◽

Adhesive Joints ◽

Stress And Strain ◽

Stress Distributions ◽

Calculation Methods ◽

Single Lap Joints ◽

Tension Testing ◽

Precise Assessment

This study presents the testing results of methacrylic adhesive single-lap joints made from elements with different stiffness and of the adhesive itself, using cast specimens. Methods for the preparation and testing of material specimens of the adhesive joints have been presented. Moreover, an attempt was undertaken to determine the strength criterion and find out which of the presented calculation methods enables the most precise assessment of strength in the tested group of single-lap joints, that differ in terms of the adhered stiffness and thickness. For this purpose, C45 steel and 5754 aluminium flat bars were bonded. Stress distributions were determined for failure forces obtained in the experiment by means of three basic analytic and numerical methods. Stress and strain states were compared, indicating the highest consistency for the value of normal peel stresses acting in the direction perpendicular to the direction of the joint tension. Reduced stresses provided by the analyses reached values higher than those which were achieved during the specimen tension testing.

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Predicting static strength in adhesively bonded single lap joints using a critical distance based method: Substrate thickness and overlap length effects

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420716666427 ◽

2016 ◽

Vol 231 (1-2) ◽

pp. 237-246 ◽

Cited By ~ 2

Author(s):

H Khoramishad ◽

A Akhavan-Safar ◽

MR Ayatollahi ◽

LFM da Silva

Keyword(s):

Longitudinal Strain ◽

Critical Value ◽

Critical Distance ◽

Static Strength ◽

Lap Joints ◽

Substrate Thickness ◽

Adhesively Bonded ◽

Single Lap Joints ◽

Failure Loads ◽

Two Parameters

A critical distance based method was proposed for predicting the strength of adhesive single lap joints. Using this method, the failure of SLJs was predicted when the longitudinal strain along the adhesive mid-plane reached a critical value at a specific critical distance. The two parameters of the method including the critical longitudinal strain and the critical distance can be determined using experimental results. Several single lap joints with different overlap lengths and substrate thicknesses were manufactured and tested under quasi-static loading. It was found that the critical distance was independent of the overlap length and the substrate thickness while the critical longitudinal strain was found to be dependent on the substrate thickness. However, the effect of substrate thickness on the critical longitudinal strain decreased by increasing the substrate thickness. The correlation between the experimental and predicted failure loads was found to be very well.

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Strength Prediction of RTM Single-Lap Joints With Transverse Stitching

Journal of Engineering Materials and Technology ◽

10.1115/1.2807018 ◽

1998 ◽

Vol 120 (4) ◽

pp. 300-303 ◽

Cited By ~ 3

Author(s):

Liyong Tong

Keyword(s):

Analytical Model ◽

Bending Moment ◽

Lap Joints ◽

Single Lap Joints ◽

Rtm Process ◽

Percent Improvement ◽

Energy Release Rates ◽

Failure Loads ◽

Transfer Moulding ◽

Transverse Stitching

It was experimentally shown that transverse stitching can provide an over 20 percent improvement in the strength of composite single-lap joints manufactured using the Resin Transfer Moulding (RTM) process. In this study, an analytical model is presented to predict the strength of the RTM single-lap joints with and without transverse stitching. Simple formulas are used to calculate the energy release rates of mode I and II using longitudinal membrane force and bending moment in a continuous adherent at an overlap end. The strengths of single-lap joints are determined using an interactive mixed-mode based failure criterion. A good correlation between the measured and the predicted failure loads validates the present analytical model.

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

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.754.252 ◽

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.

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