scholarly journals The Effect of Adhesive Layer Thickness on Joint Static Strength

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1499
Author(s):  
Marek Rośkowicz ◽  
Jan Godzimirski ◽  
Andrzej Komorek ◽  
Michał Jasztal
Keyword(s):  
Layer Thickness ◽  
Adhesive Joint ◽  
Elastic Strain ◽  
Joint Strength ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Failure Stress ◽  
Adhesive Failure ◽  
Adhesive Layers

One of the most relevant geometrical factors defining an adhesive joint is the thickness of the adhesive layer. The influence of the adhesive layer thickness on the joint strength has not been precisely understood so far. This article presents simplified analytical formulas for adhesive joint strength and adhesive joint coefficient for different joint loading, assuming, inter alia: linear-elastic strain of adhesive layer, elastic strain of adherends and only one kind of stress in adhesive. On the basis of the presented adhesive joint coefficient, the butt joint was selected for the tests of the influence of adhesive thickness on the adhesive failure stress. The tests showed clearly that with an increase in the thickness of the tested adhesive layers (up to about 0.17 mm), the value of their failure stress decreased quasi linearly. Furthermore, some adhesive joints (inter alia subjected to shearing) may display the optimum value of the thickness of the adhesive layer in terms of the strength of the joint. Thus, the aim of this work was to explain the phenomenon of optimal adhesive layer thickness in some types of adhesive joints. The verifying test was conducted with use of single simple lap joints. Finally, with the use of the FE method, the authors were able to obtain stresses in the adhesive layers of lap joints for loads that destroyed that joints in the experiment, and the FEM-calculated failure stresses for lap joints were compared with the adhesive failure stresses determined experimentally using the butt specimens. Numerical calculations were conducted with the use of the continuum mechanics approach (stress-based), and the non-linear behavior of the adhesive and plastic strain of the adherends was taken into account.

Effect of Bond Thickness on the Fracture Toughness of Adhesive Joints

2004 ◽  
Vol 126 (1) ◽  
pp. 14-18 ◽  
Author(s):  
Deok-Bo Lee ◽  
Toru Ikeda ◽  
Noriyuki Miyazaki ◽  
Nak-Sam Choi
Keyword(s):  
Fracture Toughness ◽  
Adhesive Joint ◽  
Damage Zone ◽  
Crack Tip ◽  
Adhesive Layer ◽  
Compact Tension ◽  
Optical Microscope ◽  
Adhesive Joints ◽  
Adhesive Layers ◽  
Modified Epoxy

The effect of bond thickness on the fracture toughness of adhesive joints was investigated from a microstructural perspective, using compact tension (CT) adhesive-joint specimens with different bond thicknesses. The adhesive material was a rubber-modified epoxy resin with 12.5 wt% carboxy-terminated butadiene acrylonitrile (CTBN) elastomer. The shapes of the rubber particles dispersed in adhesive layers of damaged and undamaged specimens were observed with an optical microscope. The damage was distributed along the interfaces between the adhesive layer and the two adherends. The results show that the primary causes of variations in the fracture toughness of an adhesive joint with the bond thickness are not only a damage zone around a crack tip but also the combination of a damage zone around a crack tip and additional damage zones along the interfaces.

scholarly journals Effect of Lap Length and Stiffness of Peel-Stop Fasteners in Single Lap Joints

2021 ◽  
Vol 11 (3) ◽  
pp. 1086
Author(s):  
Atsushi Takano ◽  
Chao Li ◽  
Ryuta Kitamura
Keyword(s):  
Shear Strength ◽  
Layer Thickness ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Failure Stress ◽  
Joint Failure ◽  
Single Lap Joints ◽  
Strength Tests ◽  
Strength And Stiffness

Strength tests on single lap joints with one adhesive (AV138/HV998) and one adhesive layer thickness (0.5 mm), three peel stoppers (brass bolt, nylon bolt and steel pin), and four lap lengths (12.5 mm, 25 mm, 40 mm and 100 mm) were conducted to investigate the effects of varying the lap length and stiffness of the peel-stop fasteners. Joint failure stress decreased, but failure force increased with lap length. Furthermore, joint failure stress was higher with the peel stopper. The effect of the brass-bolt peel stoppers was significant, whereas the effects of the nylon bolts and steel pins were smaller than that of the brass bolts. This indicates that the axial clamp strength and stiffness of the peel stopper are important factors in the shear strength of the lap. In addition, the effect of the stopper was negligible for the 12.5 mm lap. The reason is that the shear strength in the case of the 12.5 mm lap was large and thus the effect of the peel stopper was comparatively small. Moreover, the strength of the 100 mm lap reached the adherent material’s strength.

Strength and Finite Element Analysis of Single-Lap Joints With Adhesively Filled Columns

2002 ◽  
Author(s):  
Jiemin Liu ◽  
Songjian He ◽  
Toshiyuki Sawa
Keyword(s):  
Finite Element ◽  
Joint Strength ◽  
Fiber Composite ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Strength Increase ◽  
Element Analysis ◽  
Single Lap Joints ◽  
Novel Approach

This paper introduces a novel approach to increasing the loading ability of adhesive joints by adding adhesively filled columns. Following procedures are taken for making adhesive joints with adhesively filled columns: At first, holes are drilled at the overlap region of adherends, and then these holes are filled with adhesive or reinforced columns (such as reinforced fiber composite, metal columns, etc.). At the same time, adhesive is also applied on the surfaces of the overlap of adherends. After cured, the reinforced columns and adhesive in the holes form so-called adhesively filled columns. In this study, strengths of single-lap adhesive joints with adhesively filled columns were measured experimentally. Stress and strain distributions at typical positions in adhesive layer were analyzed by using Finite Element Method (FEM). Failure mechanics of the joint were analyzed. It was found that to well-bonded joints, the metal columns make the joint strength increase obviously and the joint strength increases with increasing of adherend thickness. Therefore, using reinforced columns in adhesive joints is an effective approach to generalizing adhesive joints from thin-walled joints to loading sizable bulk ones.

scholarly journals Strength and Failure Mechanism of Composite-Steel Adhesive Bond Single Lap Joints

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Kai Wei ◽  
Yiwei Chen ◽  
Maojun Li ◽  
Xujing Yang
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Failure Load ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Adhesive Failure ◽  
Interface Failure ◽  
Element Analysis ◽  
Single Lap Joints ◽  
Structural Adhesive

Carbon fiber-reinforced plastics- (CFRP-) steel single lap joints with regard to tensile loading with two levels of adhesives and four levels of overlap lengths were experimentally analyzed and numerically simulated. Both joint strength and failure mechanism were found to be highly dependent on adhesive type and overlap length. Joints with 7779 structural adhesive were more ductile and produced about 2-3 kN higher failure load than MA830 structural adhesive. Failure load with the two adhesives increased about 147 N and 176 N, respectively, with increasing 1 mm of the overlap length. Cohesion failure was observed in both types of adhesive joints. As the overlap length increased, interface failure appeared solely on the edge of the overlap in 7779 adhesive joints. Finite element analysis (FEA) results revealed that peel and shear stress distributions were nonuniform, which were less severe as overlap length increased. Severe stress concentration was observed on the overlap edge, and shear failure of the adhesive was the main reason for the adhesive failure.

Fracture Characterization of Adhesive Joints in Carbon/Epoxy Wind Turbine Blades

2012 ◽  
Author(s):  
Yi Hua ◽  
Linxia Gu
Keyword(s):  
Shear Modulus ◽  
Wind Turbine ◽  
Adhesive Joint ◽  
Turbine Blades ◽  
Adhesive Layer ◽  
Adhesive Joints ◽  
Wind Turbine Blades ◽  
Fracture Characterization ◽  
Initiation And Propagation

The objective of this work is to predict the fracture behavior of adhesive joints in the 4-ply carbon/epoxy wind turbine blades through finite element method. The influence of through-thickness flaw in the adhesive layer was examined. The contour integral method was used for evaluating the stress intensity factors (SIF) at the flaw tips, while the strength of the joint was assessed through the crack initiation and propagation simulation. The effect of adhesive shear modulus has also been investigated. Results suggested that the maximum stress occurred at the adhesive-shell interface and increased stress levels were observed in the case of adhesive layer with flaw. It also highlighted distinct edge effects along the thickness of the adhesive joint. Compared to the perfect adhesive, the static strength of the adhesive joint with flaw remained unchanged. Large shear modulus of the adhesive diminished the strength of the adhesive joint with the increased SIF.

A Theoretical Model for Nondestructive Evaluation of Damage of Adhesive Joints

2006 ◽  
Vol 324-325 ◽  
pp. 339-342 ◽  
Author(s):  
Guo Shuang Shui ◽  
Yue Sheng Wang ◽  
Jian Min Qu
Keyword(s):  
Elastic Modulus ◽  
Theoretical Model ◽  
Adhesive Joint ◽  
Integral Transform ◽  
Nonlinear Coefficient ◽  
Adhesive Layer ◽  
Adhesive Joints ◽  
Ultrasonic Waves ◽  
Transform Method ◽  
Nonlinear Ultrasonic

In this paper, a new theoretical model is developed to characterize the damage of the adhesive joint. Elastic modulus of adhesive joints is an important parameter to represent damage characteristics. Based on the fact that the thickness of the adhesive layer is very small, it is reasonable to believe that damage will decrease the tension modulus of the adhesive joint while the compression modulus will keep unchanged. Modeling the adhesive joint as an interface with different modulus in tension and compression, and applying integral transform method, we solve the associated nonlinear boundary problem to obtain the nonlinear ultrasonic waves transmitting through the adhesive layer. With this nonlinear ultrasonic wave, variation of elastic modulus and damage variable of the adhesive layer are thereafter characterized nondestructively by a nonlinear coefficient.

Parametric Study of Combined Adhesive-Riveted Lap Joints

2004 ◽  
Vol 261-263 ◽  
pp. 399-404 ◽  
Author(s):  
Thongchai Fongsamootr ◽  
Charoenyut Dechwayukul ◽  
Notsanop Kamnerdtong ◽  
Carol A. Rubin ◽  
George T. Hahn
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Layer Thickness ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Adhesive Layer ◽  
Lap Joints ◽  
Single Row ◽  
Riveted Lap Joints ◽  
Panel Thickness

Riveted lap joints are widely used to assemble complex structures, e.g. aircraft fuselages. A thin layer of adhesive (sealant), is normally applied to lap joints in order to restrict the entry of moisture and retard corrosion. In this work, combined adhesive-riveted lap joints were studied to understand the effect of three parameters: panel thickness, adhesive stiffness and adhesive layer thickness, on single row non-countersunk riveted lap joints. Finite element analysis (FEA), along with Thin Adhesive Layer Analysis (TALA-developed for simulating the adhesive layer in lap joint models), were used to analyze the joint behavior. In previous studies, the stress concentration factor for single row riveted lap joints was found to be approximately 6.1, and the stress concentration factor for sealed riveted lap joints was approximately 5.2 for a 180 micron thick sealant layer. In this study, panel thickness, adhesive stiffness and adhesive layer thickness were varied parametrically in FEA analyses to determine their affects on the joints. The FEA/TALA results were used to predict the fatigue life of the joints as functions of the three parameters. The results show that the maximum tensile stress is smaller with a smaller panel thickness. The results also showed that the stress concentration factor in the joints was reduced when the stiffness of the adhesive layer was increased or when the thickness of the adhesive layer was decreased. Finally, fatigue tests showed that the fatigue life of the combined adhesive-riveted lap joints was greater than for riveted lap joints without adhesive.

Numerical modelling of functionally graded adherends

2020 ◽  
pp. 095440622096769
Author(s):  
MQ dos Reis ◽  
RJC Carbas ◽  
EAS Marques ◽  
LFM da Silva
Keyword(s):  
Joint Strength ◽  
Adhesive Bonding ◽  
Adhesive Layer ◽  
High Strength ◽  
Lap Joints ◽  
Bond Line ◽  
Functionally Graded ◽  
Metal Alloys ◽  
Adhesive Properties ◽  
Main Research

The development of lighter structures and materials has been one of the main research concerns of the transportation industry during the last decade, driven by the necessity to decrease fuel consumption and emissions. Therefore, the use of several different new lightweight materials, such as special metal alloys, reinforced polymers and new advanced composite materials has been explored, leading to optimized structures which combine these novel materials. To manufacture these multi-material structures, adhesive bonding is one of best joining techniques available, as fasteners add weight to the structure and require holes to be drilled and welding is not easily applicable to reinforced plastics, composites and some high strength metal alloys. However, adhesive bonding also presents some limitations that need to be considered, such as the appearance of singularities and the resultant stress concentration at the edges of the bond line, which result in a reduction of the joint strength. In order to mitigate this effect, several techniques have been proposed, being the use of functionally graded adherends one of them. Functionally graded adherends consist in an adherend where the mechanical properties gradually change throughout the material, usually in the thickness or length direction. The present work introduces the concept of a layered functionally graded adherend, varying the flexibility of each layer through the thickness direction. Different ratios of stiffness variation, combined with different adhesive properties, were numerically evaluated for single lap joints, comparing the stress distribution of the adhesive layer and the resultant joint strength, using cohesive zone modelling. Moreover, an optimization process of typical graded material properties, where different distribution laws that consider material weight and strength are considered, is presented.

Use of the Fokker Bond Tester on Joints with Varying Adhesive Thickness

1987 ◽  
Vol 201 (1) ◽  
pp. 41-49 ◽  
Author(s):  
C C H Guyott ◽  
P Cawley ◽  
R D Adams
Keyword(s):  
Layer Thickness ◽  
Natural Frequencies ◽  
Adhesive Layer ◽  
Adhesive Joints ◽  
Cohesive Strength ◽  
Piezoelectric Crystal ◽  
Adhesive Properties ◽  
Resonant Frequencies ◽  
Wide Range ◽  
Adhesive Thickness

The operation of the Fokker bond tester has been investigated. The instrument monitors one of the natural frequencies of the system comprising a piezoelectric crystal coupled to the joint under test. The resonant frequencies of two different sizes of transducer coupled to both plain plates and adhesive joints have been investigated both theoretically and experimentally, the measured values being in line with the predictions. It has been concluded that the method is satisfactory for the location of disbonds in a multi-layer construction but that it cannot distinguish between adhesive modulus and adhesive layer thickness. Both of these parameters affect the adhesive stiffness and hence the measured resonant frequencies. However, they have different effects on the cohesive strength of the adhesive so unless independent measurements of, for example, thickness are made, erroneous strength predictions may be obtained. Also, the measured frequencies are independent of adhesive stiffness over a wide range of typical stiffnesses, so changes in adhesive properties will not be measured in these cases.

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