Single Lap Composite Joints Research Papers (original) (raw)

2025, Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science

The joining techniques of lightweight and strong materials in the transport industry (e.g. automotive, aerospace, shipbuilding industries) are very important for the safety of the entire structure. In these industries, when compared with other joining methods, the use of adhesively bonded joints presents unique properties such as greater strength, design flexibility, and reduction in fuel consumption, all thanks to low weight. The aim of this study was the analysis of the tensile fatigue behavior of adhesively bonded glass fiber/epoxy laminated composite single-lap joints with three different specimen types including 30, 40 and 50 mm overlap lengths. In this study, composite adherents were manufactured via vacuum-assisted resin transfer molding and were bonded using Loctite 9461 A&B toughened epoxy adhesive. The effect of a surface treatment method on the bonding strength was considered and it led to an increment of about 40%. A numerical analysis based on a finite element model was...

2025, international journal of advanced design and manufacturing technology

Purpose of this study is to obtain failure modes and failure loads of two Parallel pin loaded holes in unidirectional glass fibre/epoxy by adding nanoclay in the absence of nanoclay composite laminates using finite element analysis; the results are validated through experiment. The geometrical parameters studies in this survey include the distance between the diameter of the hole (e/d) and the free edge of specimen, the distance between two holes-to-hole diameter (M/d). The samples were exposed to constant speed tensile loading. The results showed that by adding nanoclay, failure load increases and failure modes varies from shear out to bearing failure. Furthermore, increasing distance from the free edge of the pin centre's increases load bearing capacity of two type of composite materials and changes the failure mode from shear to the bear, it increases and decreases the distance from canter's of pin in layers with and without nanoclay particles, respectively and changes failure mode from shear to bear mode. In order to find morphology of specimens and dispersion quality, Scanning Electron Microscope (SEM) was used. For predicting failure load and differentiating failure modes, Tsai-hill failure criteria associated with material property degradation is used. Experimental and FEM results indicate importance of considering the impact of e/d and M/d ratios in the design of two Parallel pin joints. ANSYS was used to carry out numerical simulation and the results denote a good agreement between numerical and experimental results. In this study, by designing an experimental and numerical procedure to estimate the effect of nanoclay, on failure mode and failure load of typical composite material, glass-epoxy, we could illustrate that adding nanoclay brought with it improvement of shear and tensional strength of glass-epoxy about 10 %.

2025, international journal of advanced design and manufacturing technology

2025, International Journal of Materials and Product Technology

Due to their longevity, ease of instalation and reduced stress concentration, among several other positive attributes, adhesively bonded joints are being widely used in mating fibre-reinforced plastic (FRP) composite adherends in petrochemical industry. The study of bonded joints, as opposed to the conventional mechanically fastened joints, has therefore gained great importance. The work presented in this paper follows a comprehensive series of studies being conducted within our research group in characterising the performance of bonded joints in pipes subjected to torsional loading. The study of bonded joints under static and cyclic torsional loading is extremely scarce in the literature, thus, it has been the motivation for this work. This study examines the influence of bond (overlap) length on the performance of single lap adhesively bonded joint within FRP tubular adherends subject to static and cyclic torsional loading conditions. Both experimental and computational methods are used in the investigation to characterise the behaviour of the joint. Different failure modes are observed as a result of issues related to the overlap length and bond fabrication. The concept of 'effective bond length' is also discussed in detail, with a critical view on its usage in practice.

2024, International Journal of Adhesion and Adhesives

The simplicity and efficiency of the adhesive joints have increased more and more their use in many fields. In ship construction the need to join different materials, such as the bonding of the hull/deck, the sea chest, the portholes, the windshields, the panels of cabins, etc. leads to choosing increasingly the adhesive joints. In this work we have evaluated the effects of both SMP (Silyl Modified Polymer) based adhesives and sealants on single lap joints (SLJs) with dissimilar substrates. Three pairs of single lap joints were taken into account among dissimilar adherends: stainless steel (AISI 316) with PMMA (or Altuglas s) and monolithic composite laminates bonded with glass or PMMA. Before tensile testing some SLJ samples were subjected to a three-dimensional computed tomographic analysis to evaluate how the presence of possible defects in the adhesive layer affects the failure mode. A design of experiments was defined in order to quantify the effect of the considered factors and their correlation. The obtained maximum tensile stress values confirm the data provided by the manufacturer, approximately between 2 and 2.5 MPa, showing generally cohesive fracture. Finally the considered SMP adhesives and sealants are well suited for the chosen different substrates, although special attention should be placed on the glass-GFRP joint as it is confirmed by statistical analysis.

2024

Adhesively bonded joints are increasingly being used in joining various structural components made of FRP laminated composites. Adequate understanding of the behavior of adhesively bonded joints is necessary to ensure efficiency, safety and reliability of such joints. While single lap joint has received considerable attention, very little work has been carried out on the double lap joint configuration. The present investigation deals with the static analysis of adhesively bonded double lap joint in laminated FRP composites using three-dimensional theory of elasticity based finite element method. The finite element model is validated with the theoretical concepts. The double lap joint made of generally orthotropic laminates subjected to longitudinal loading is analyzed. The out-of-plane normal and shear stresses are computed at the interfaces of the adherend and adhesive, and at mid surface of the adhesive for different ply orientations in the double lap joint are considered for the ...

2024, International journal of applied research

2024

In this work, the effect of an Ytterbium fibre laser treatment on the adhesive properties of scarf bonded carbon fibre reinforced plastics (CFRP) joints has been investigated. The surfaces were scarfed and afterwards laser treated. The effect of laser treatment on the surface morphology was investigated with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The laser treatment resulted in a morphological and chemical change on the CFRP surface. The introduced thermal energy was able to partly strip and roughen up the carbon fibres. The laser treatment increased the carbon and decreased the oxygen, nitrogen and sulphur content on the surface. With the laser treatment the static and fatigue strength of the scarf bonded joints could be improved.

2024, International Journal of Adhesion and Adhesives

This work emphasizes the critical need of surface preparation to improve the performance of adhesively bonded 3D printed Acrylonitrile Butadiene Styrene (ABS) adherends obtained using Fused Filament Fabrication (FFF). In particular, mechanical abrasion and two different plasma pretreatments, i.e., Atmospheric Pressure Plasma (APP) and Low-Pressure Plasma (LPP), were compared through the qualitative analysis of surface wettability, using static and dynamic contact angle measurements, and the quantitative evaluation of surface roughness measured using optical profilometry. In addition, mechanical tests were carried out using the single lap joint configuration and the interaction between the treated ABS substrates and three different adhesive materials, epoxy, polyurethane and modified silane, were carefully ascertained. The results indicated that the plasma process at low pressure (LPP) enabled a substantial decrease of contact angle (<10 o), with little modifications of surface morphology and topography with respect to the reference solvent cleaned surface (>80 o). The improved wetting was accompanied by a relevant increase in the joint strength. The actual mechanism of fracture shifted from adhesive failure, typical of solvent cleaned and abraded surfaces, to full cohesive failure within either the substrates of the adhesive layer. Besides, a strong influence of the adhesive selected for manufacturing was reported. Indeed, using a tough bi-component epoxy adhesive in conjunction with the LPP pre-treatment led to substrate failure, representing the largest possible enhancement of joint strength. The shear strength was over 300% of that obtained with reference solvent cleaned, and 80% larger than that recorded on abraded surfaces.

2024

Adhesively bonded joints are increasingly being used in joining various structural components made of FRP laminated composites. Adequate understanding of the behavior of adhesively bonded joints is necessary to ensure efficiency, safety and reliability of such joints. While single lap joint has received considerable attention, very little work has been carried out on the double lap joint configuration. The present investigation deals with the static analysis of adhesively bonded double lap joint in laminated FRP composites using three-dimensional theory of elasticity based finite element method. The finite element model is validated with the theoretical concepts. The double lap joint made of generally orthotropic laminates subjected to longitudinal loading is analyzed. The outof-plane normal and shear stresses are computed at the interfaces of the adherend and adhesive, and at mid surface of the adhesive for different ply orientations by varying the width of the double lap joint are considered for the analysis. It was predicted that when the fiber angle increases the stiffness of the plate in the longitudinal direction decreases and the interlaminar stresses at joint interfaces increases due to the effect of coupling and also the longitudinal displacement increases.

2024, International Journal of Adhesion and Adhesives

This paper presents systematic numerical study of stresses in the adhesive of a single-lap joint with the objective to improve understanding of the main material and geometrical parameters determining performance of adhesive joints. For this purpose a 3D model as well as 2D model, optimized with respect to the computational efficiency by use of novel displacement coupling conditions able to correctly represent monoclinic materials (off-axis layers of composite laminates), are employed. The model accounts for non-linearity of materials (adherend and adhesive) as well as geometrical nonlinearity. The parameters of geometry of the joint are normalized with respect to the dimensions of adhesive (e.g. thickness) thus making analysis of results more general and applicable to wide range of different joints. Optimal geometry of the single-lap joint allowing to separate edge effect from end effects is selected based on results of the parametric analysis by using peel and shear stress distributions in the adhesive layer as a criterion. Three different types of single lap joint with similar and dissimilar (hybrid) materials are considered in this study: a) metal-metal; b) compositecomposite; c) composite-metal. In case of composite laminates, four lay-ups are evaluated: unidirectional ([0 8 ] T and [90 8 ] T) and quasi-isotropic laminates ([0/45/90/-45] S and [90/45/0/-45] S). The influence of the abovementioned parameters on peel and shear stress distributions in the adhesive layer is examined carefully and mechanical parameters governing the stress concentrations in the joint have been identified, this dependence can be described by simple but accurate fitting function. The effect of the used material model (linear vs non-linear) on results is also demonstrated.

2024, Composites Part B: Engineering

The Fiber-Tear-Failure (FTF) is a common mode of failure in the adhesively bonded single lap joint having continuous fiber reinforced composite. Within single lap joints, presence of material and geometric discontinuities restrict the applicability of strength of material based approach for failure load prediction. Zone based approach appears promising in tackling discontinuity issues provided the right failure criterion and critical zone size are known. In this paper, a right failure prediction criterion is identified that can be used for the Fiber-Tear-Failure load prediction using zone based approach. Using a carbon fiber composite and an epoxy paste adhesive, failure modes were generated experimentally using different dimensions of lap joints. Several stress/strain based failure criteria for composite were tested. Critical zone size was calculated by performing the finite element analysis on a single lap joint with known failure load. For other joints, failure loads were calculated by adjusting the input loads in the analysis such that the failed zone size became the same as the critical zone size. The result reveals that Azzi-Tsai (Norris) criterion is capable of predicting failure loads of single lap joints with FTF.

2024, Muğla journal of science and technology

This paper aims to determine of thermal shear stresses on thermoplastic adherents which are joined by hybrid type. It is designed both adhesive and two parallel pins. Both plotting and solving of this problem were done using ANSYS software. Therefore solutions were performed with finite element methods (FEM). Modeling of hybrid joint was established as three dimensional. Thermal stresses were caused to apply uniform thermal loads on designed structure. Determined results pointed out that thermal shear stresses were strictly affected of increasing uniform thermal loads. Briefly, their values were increased by increasing of thermal loadings.

2024, Advances in Science and Technology Research Journal

This paper presents the experimental results of a study investigating the effect of holes and notches made on the overlap ends on the strength of adhesive joints. Single-lap joints made of S235JR steel sheets bonded with Araldite 2024-2 epoxy adhesive were tested. For comparative reasons, static shear strength tests and high-cycle fatigue strength tests were performed. Adhesive-filled joints having three holes, each with a diameter of 3 mm, and notches, each 3 mm wide and 4 mm long, were tested and compared with reference joints, i.e. without modification. The assumption was to determine whether the structural modifications would reduce the peak peel and shear stresses that are typical of this type of joints. Results of the static strength tests showed no significant effect of the applied modifications on the strength of the joints. However, in terms of fatigue strength, the results demonstrated a significant improvement in fatigue life, the value of which increased in the low-cycle fatigue region by 328.6% for the joint with notches and by 640.8% for the joint with holes. A smaller yet still positive effect of the applied modifications was shown for high-cycle fatigue. For a variable load with the maximum value of 9 MPa, the fatigue life increased by 215.9% for the variant with notches and by 183.3% for the variant with holes. Surface topography of fatigue fractures was examined by determining roughness parameters on the overlap ends in the samples. Significant differences were shown, with the selected roughness parameters being significantly lower for the reference variant than for the variants with notches and holes. It was shown that the applied structural modifications led to increasing the fatigue strength to 8.5 MPa for the limit number of cycles equal to 2•106, when compared to the reference variant for which the fatigue strength was 8 MPa.

2024, Composite Structures

Durability of composite assemblies under extreme conditions: Thermomechanical damage prediction of a doublelap bonded composite assembly subject to impact and high temperature, Composite Structures (2019), doi:

2024, Lecture Notes in Mechanical Engineering

The three-dimensional (3-D) variation of stresses of the single lap joint (SLJ) made from hard steel and epoxy (AV119) under tensile loading is studied using 3-D FE (finite element) analysis. The peel (tension) stress, direct shear (inplane shear) stress and transverse shear (out-of-plane shear) stress are the responsible for opening (mode-I), sliding (mode-II) and tearing (mode-III) mode of failures, respectively, are computed in the overlap region of the joint. Thin adhesive layer used to join the upper (lap) adherend and the lower (strap) adherend is modelled by surface to surface contact elements. The nonlinear material properties of adhesive and adherend (stress and strain graph obtained from the experiments) are input to the finite element programme. The results show that the variations of peel stress and shear stresses in the overlap region are very complicated in nature and hence a 3-D FE analysis is recommended to have a clear visualisation of these stress variations. The peel stress among all the failure-inducing stresses at the overlap ends are dominant and important for adhesive bonded joint as adhesives are weaker than the stronger adherends. The results of the 3-D FE analysis of the SLJ are in good agreement with the experimental results. This research work is may be considered as detail study of the stress distributions in the vulnerable region of the joint under tensile loading.

2024, Progress in additive manufacturing

A number of different parts for mechanical testing were produced using composite metal foil manufacturing (CMFM). This process is a combination of laminated object manufacturing and brazing technology. Aluminium is one of the toughest metals to join and CMFM can achieve this task with ease. By using aluminium 1050 foils of 0.1 mm thickness, various parts were made according to British and International Standards, including lap joints, peel specimens, dog-bone specimens and tested for their mechanical properties. A special, 80 % zinc and 20 % aluminium by weight, brazing paste was utilized for joining the foils together. The test of the single lap joints show that none of the specimens failed at the bonded area and the failure was always due to fracture of the parent metal. Cohesive failure was also observed for the single lap joints by using 10 mm thick aluminium metal plates. It helped in calculating the lap shear strength which is a useful design parameter. The peel test showed good bond consistency in all the specimens with an average peel strength of 20 MPa. Comparative tensile test was conducted with a dog-bone specimen machined from a solid block of aluminium 1050 and specimens made with CMFM. The results showed that the specimens made by CMFM fracture at force values that are higher than that of the parent metal. This demonstrates that CMFM has the capability to produce high quality and stronger parts as compared to conventional machining methods employed for the production of metal parts. The effect of using different number of layers for the same cross-sectional area has also been investigated. Keywords Additive manufacturing Á Brazing Á Laminated object manufacturing Á Lap-shear testing Á Metal foil Á Metal parts Á Peel test Á Tensile testing & Javaid Butt

2023

In this paper by employing ANSYS Workbench software and three-dimensional finite element simulation, failure analysis of hybrid bonded and bolted single and double lap joints with laminated composite adherends subjected to axial, shear and bending loads were performed. In order to select an appropriate and optimized element number, the convergence behavior of single and double lap joints were investigated. Then the failure study of each single and double lap hybrid composite joints for the three time dependent loading cases were performed. To demonstrate the validity and precision of the presented simulations, the obtained results were compared with the results presented in the available literatures. The results of this research indicated that, in the single lap joint subjected to axial load, the replacement of hybrid bonded bolted joint instead of adhesive joint leads to significant increase of 56% in the load bearing capacity of the joint.

2023, Mechanics of Advanced Composite Structures‎

Adhesive joint Adherend Transient dynamic Laminated Composite Peel and shear stresses A novel semi analytical method is developed for transient analysis of single-lap adhesive joints with laminated composite adherends subjected to dynamical loads. The presented approach has the capability of choosing arbitrary loadings and boundary conditions. In this model, adherends are assumed to be orthotropic plates that pursuant to the classical lamination theory. Stacking sequences can be either symmetric or asymmetric. The adhesive layer is homogenous and isotropic material and modelled as continuously distributed normal and shear springs. By applying constitutive, kinematics, and equations of motions, sets of governing differential equations for each inside and outside of overlap zones are acquired. By solving these equations, the time dependent shear and peel stresses in adhesive layer as well as deflections, stress resultants, and moment resultants in the adherends are computed. The developed results are successfully compared with the experimental research presented in available literates. It is observed that the time variations of adhesive peel and shear stress diagrams are asymmetric for the case of symmetric applied load with high variation rate. Moreover, it is reported that although the magnitude of applied transverse shear force is reduced to 10% of applied axial force, however a significant increase of 40% in the maximum peel stress attained.

2023, International Journal of Engineering

In this paper, considering an adhesively bonded composite single-lap joint, a novel approach is presented to predict the peel and shear stress distributions of the adhesive layer for an ASTM standard test sample. In the current method, the equilibrium equations are derived using the energy method and based on the Timoshenko's beam theory. Two solution procedures then are discussed; one of them represents a solution approach based on the direct variational method allied with use of the Ritz approximation; while the second one is based on a linear estimating function. Unlike previous methods, in which the variation of stress through the thickness of adhesive is neglected or is assumed to be linear and they cannot be used to analyze the joints with thick adhesive layers; considering the effects of adhesive thickness makes it possible to employ present method to analyze the joints with thick adhesive layers as well as thin ones.

2023, Journal of Applied Mechanics and Technical Physics

Three-dimensional explicit dynamic simulations are carried out to study the failure of hybrid bolted-bonded vertical T-and L-joints under noncontact underwater explosion shock pressure. In this modelling, adherends are fibrous laminated composites having an orthotropic behavior, while bolts and adhesive layers exhibit an isotropic behavior. It is found that hybrid vertical T-and L-joints display appreciably higher joint resistance to underwater explosion shock pressure than adhesive Tand L-joints.

2023

An integral shaft bearing is popular for carrying higher specific load capacity, preventing misalignment defects and eliminating the risk of undesirable distortion of bearings, in compression to any other bearings. Integral shaft bearing are used to reduced rotational friction and support, axial and radial loads which generate friction and increased temperature and stresses inside the bearings. If the generated heat cannot be properly removed from the inside bearing ,the temperature might exceed certain limit. Due to which the bearing should be fail. That why I analyze heat flow, temperature distribution and stress in a bearing system, a typical integral shaft bearing and its environment has been design and analyze the system using the famous finite elements tool ANSYS workbench 14.0. In this research, structural and thermal characteristics performance of integral shaft bearing to Analyze stress, thermal elongation and temperature distribution due to friction also its effect on bear...

2023, Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications

Growing awareness about sustainable development and the environmental problems involved in using nonbiodegradable materials has motivated the research community to develop environment-friendly materials. Developments have been achieved in the field of natural fibers and biopolymers, still there remain unanswered questions regarding the high-quality cost-effective manufacturing of natural fiber reinforced composites. The natural fiber-based polymeric composites are being used extensively in engineering applications, especially in the nonstructural parts and components. Near-net processing techniques such as compression molding, extrusion, and injection molding are well-developed for natural fiber reinforced composites. However, secondary processes such as joining, machining, and surface modification are still unexplored and need to be investigated in detail. The present research endeavor is an attempt to experimentally investigate the adhesive joining behavior of jute/sisal reinforced epoxy composites. The laminates based on three different material configurations in woven mat form, namely, pure jute, pure sisal, and hybrid jute/sisal reinforced epoxy have been fabricated by hand layup process. Different lap joint configurations with through holes in adherends overlapping area have been investigated. It has been established experimentally that the holes in the adherends provide a hinge-effect in the overlapping area and help in defining the failure load of the composite joint. The different arrangement of holes has been investigated and the best design of hole arrangement has been proposed for adhesive joining of jute/ sisal fiber reinforced epoxy laminates. It was found that the holes (filled with an epoxy adhesive) in the overlap area result in 6-18% improvement in the failure load for different materials as compared to the joints with only adhesive bonding. Moreover, the field-emission scanning electron microscopy micrographs have been used to understand the failure mechanism of the adhesively bonded natural fiber reinforced composite laminates.

2023, American journal of mechanical engineering

Single Lap Joints are used extensively in the aerospace industry due to their lower weight and absence of stress concentration due to drilled holes. However, their lesser strength remains an important limitation. Different modes of failures have been reviewed in this article. The bond strength of a single lap joint can be varied by varying its overlap length, while, the strength does not strictly increase with increasing bonding length. Rather, it increases up to an optimum value and decreases further. This optimum value was obtained, which is found to be in agreement with previous studies in this regard. The surfaces of the bonded aluminum plates were modified by generating notch shaped pattern on bonding area. Due to notch pattern of bonding, the bond strength increases up to 75˚ notch angle and then decreases with further increase in the notch angle. The experimental results of bonded joints without notch also were obtained by software analysis. Maximum strength of joint length reached at optimum length and optimum notched surface pattern.

2023, Advances in Science and Technology Research Journal

2023

Adhesively bonded joints are increasingly being used in joining various structural components made of FRP laminated composites. Adequate understanding of the behavior of adhesively bonded joints is necessary to ensure efficiency, safety and reliability of such joints. While single lap joint has received considerable attention, very little work has been carried out on the double lap joint configuration. The present investigation deals with the static analysis of adhesively bonded double lap joint in laminated FRP composites using three-dimensional theory of elasticity based finite element method. The finite element model is validated with the theoretical concepts. The double lap joint made of generally orthotropic laminates subjected to longitudinal loading is analyzed. The outof-plane normal and shear stresses are computed at the interfaces of the adherend and adhesive, and at mid surface of the adhesive for different ply orientations by varying the width of the double lap joint are considered for the analysis. It was predicted that when the fiber angle increases the stiffness of the plate in the longitudinal direction decreases and the interlaminar stresses at joint interfaces increases due to the effect of coupling and also the longitudinal displacement increases.

2023, Composites Part B: Engineering

This paper deals with the structural design of single lap joints (SLJs) with delaminated adherends using fracture mechanics principles. The interlaminar stresses and Strain Energy Release Rate (SERR) are considered as damage characterizing parameters used for designing the SLJ when delamination damages are pre-embedded in both the adherends at similar positions. Three dimensional geometrically non-linear finite element analyses (FEAs) of SLJ with delaminated adherends have been performed to determine the interlaminar and SERR values along the delamination fronts by simulating the simultaneous interaction delamination damages when pre-embedded at similar positions in both the adherends. SERR values are evaluated using Modified Crack Closure Technique (MCCI) which is based on energy principle. The delaminations are assumed to be of linear front, and have been considered to be embedded in both the laminated FRP composite adherends beneath the surface ply of the adhesively bonded SLJ. The delamination damages are presumed either to pre-exist or get evolved at the interlaminar locations. Such delaminations have been modelled using the sublaminate technique. The critical issues of modelling pre-embedded delamination damages are discussed in detail. The numerical results presented in this paper are based on the validated FE model compared with the available literature. Based on the present analyses, the structural design recommendations have been made for the SLJ when pre-embedded delamination damages are present in both the adherends. It is observed from the stress based design that the delamination damage when present in the bottom adherend is more detrimental for failure of SLJ compared to that for the case when it is present in the top adherend. Also, SERR based design reveals that the opening mode predominantly governs the propagation of delamination damage for all positions of the pre-embedded delaminations in both the adherends of the SLJ.

2023, American journal of mechanical engineering

2023, International Journal of Adhesion and Adhesives

This work encompasses the study of the mechanical behavior of single lap joints (SLJ) with similar and dissimilar materials, joined by epoxy adhesives. The objective was to analyze the effect of the variables overlap length (OL), adhesive thickness (AT) and adherends yield strength (YS) over the SLJ failure load (FL). The stress state of the joints was analyzed through an optical technique. Tensile tests were performed with samples containing three levels of the factors OL, AT and YS. This last variable analysis was performed using aluminum (AA5083 H111) and high strength steel (DP600) adherends, combined in three different levelssimilar AA, similar HSS and dissimilar. The digital image correlation (DIC) technique was used in order to analyze and quantify the incidence of deformation on the adherends and adhesive during the tensile tests, in order to verify how the tensile load was distributed through the SLJ of this work. All the variables had significance over the SLJ. The OL increased the SLJ FL, but the effect reduced as the length is increased. The adherends YS also increased the SLJ FL, but not as much as the OL. Plastic deformation of the adherends leaded to the onset of high peeling stress, which reduced considerably the joints FL. The AT had a negative effect over the SLJ FL. This relationship varied when the adherends faced remarkable plastic strain.

2023, Composite Structures

The aim of this study is to investigate the effect of the adherend material on the mode I fracture behaviour of bimaterial composite bonded joints. Both single-material (steel-steel and composite-composite) and bi-material (steel-composite) joints bonded with a structural epoxy adhesive are studied. Additionally, two adhesive bondline thicknesses are considered: 0.4 mm (thin bondline) and 10.1 mm (thick bondline). The Penado-Kanninen reduction scheme is applied to evaluate the mode I strain energy release rate. The results show that the mode I fracture energy, G Ic , is independent of the adherend type and joint configuration (single or bi-material). G Ic shows average values between 0.60 and 0.72 N/mm for thin bondlines and 0.90-1.10 N/mm for thick bondlines. For thin bondlines, the failure is cohesive and the similar degree of constraint that is imposed to the adhesive by the high-modulus (i.e., steel) and/or relatively thick (i.e., composite) adherends results in similar values of G Ic for both single-and bi-material joint types. For thick bondlines, the crack grows closer to one of the adhesiveadherend interfaces, but still within the adhesive. The results show that the adhesive could deform similarly, although the crack has been constrained on one side by different types of adherends, either a steel or composite.

2023

On the influence of overlap topology on tensile strength of composite bonded joints A multistacking design

2023, Composites Part B: Engineering

An essential question to predict the structural integrity of bi-material bonded joints is how to obtain their fracture properties under pure mode I. From open literature, it is found that the most commonly used design criterion to test mode I fracture is matching the flexural stiffnesses of the two adherents in a DCB coupon. However, the material asymmetry in such designed joints results in mode II fracture as well. In this paper, a new design criterion is proposed to obtain pure mode I fracture in adhesively bonded bi-material DCB joints by matching the longitudinal strain distributions of the two adherends at the bondline-longitudinal strain based criterion. A test program and Finite Element modelling have been carried out to verify the proposed design criterion using composite-metal bonded DCB joints. Both the experimental and numerical results show that pure mode I can be achieved in bi-material joints designed with the proposed criterion. G II /G I ratio is reduced by a factor of 5 when using the proposed longitudinal strain based criterion in comparison with the flexural stiffness based criterion.

2023, SN Applied Sciences

The high fracture strength and exceptional impact resistance of polymer-based composites are of paramount importance to various industries like aerospace, automotive, and construction. The resin transfer molding (RTM) process is used to produce composite samples of superior quality, minimal porosity, and reduced lamination defects. In the present study, the RTM method was employed to fabricate glass fiber-reinforced composites, aiming to investigate their specific mechanical properties and structural performance. The study initially determined the ballistic limit of the produced samples. Subsequently, experimental investigations were carried out to examine the impact of hole drilling on the tensile strength, flexural strength, and impact resistance of the samples. The results revealed that the produced polymer plate demonstrated a ballistic limit with a pressure of 11 bar and a speed of 104 m/s, leading to ball restriction in the plate. The sample without holes showed the highest fracture force, while samples with three and five holes exhibited reduced fracture forces. Additionally, bending force and impact resistance were lower in samples with multiple holes compared to the sample without holes. The impact resistance of the sample with five holes was the lowest among all configurations. The study revealed that the presence of three holes arranged in a row has a lesser impact on reducing the ultimate tensile force compared to the effect of five holes. Moreover, the bending test results indicated that sample failure occurred on the side under tension, resulting in higher bending forces than tensile forces. Article highlights • Using resin transfer molding (RTM) method to produce high quality polymeric composite samples. • Determination of ballistic limit of glass fiber-reinforced composite samples. • Evaluation of the influence of the hole drilling on the tensile strength, flexural strength, and impact resistance of the samples. • Analysis of bonding and microstructural of the samples by SEM and EDX tests.

2023, DergiPark (Istanbul University)

In this study, surface patterning with CNC vertical machining center was applied to the aluminum surface for the enhancement of the shear strength of the epoxy-bonded lap joints. It was found that the pattern shape affected shear strength and among vertical, square, horizontal, 45 degree and diamond patterns, 45-degree provided the highest shear strength of 24.6 MPa. Moreover, the pattern features also affected the shear strength. A decrease in the depth led to slightly lower shear strength, whereas an increase in the depth gave a slight enhancement. The optimum depth was found as 300 μm and the obtained shear strength was calculated as 25.5 MPa. Additionally, an increase in the width length led to lower shear strength. On the other hand, a decrease in the width length provided higher shear strength. The increment became smaller as the width length increased. Also, after a point, the trend reversed and the shear strength decrease slightly. The optimum width length and the corresponding shear strength were found as 1.0 mm and 28.0 MPa, respectively.

2023

According to the fracture mechanics concept, the distribution of three-dimensional (3-D) three major stresses, i.e. peel stress for mode I, direct shear stress for mode II and transverse shear stress for mode III, are computed at different interfacial layers on curved laminated FRP composite single lap joint (SLJ), subjected to different ply orientation in adherend with application of tensile load. The three interfacial adhesive layers have been considered as; bottom layer (in between lower adherend and adhesive layer), middle layer (mid plane of adhesive layer) and top layer (in between upper adherend and adhesive) for determining the critical location of damage initiation by using failure index criteria. The results show that the variations of peel stress and shear stresses in the overlap region are very complicated in nature and hence a 3-D finite element analysis (FEA) is recommended to have a clear visualization of these stress variations. A comparative analysis due to ply orientation of adherends of SLJ has been carried out. It has been observed that the adhesion failures (in between adherend and adhesive) are more dominated than cohesion failure (within the adhesive layer).

2023

Effect of combined tensile-torsional loads on the structural integrity of adhesively bonded curved laminated FRP composite single lap joint. Research aim: According to the fracture mechanics concept, the distribution of three major stresses, i.e. peel stress, direct shear stress and transverse shear stress are analysed of this single lap joint (SLJ) subjected to different ply orientation on adherend with application of both tensile and torsional loads.

2023

The present research aims to study the growth of the circular adhesion failure pre-existing at the interfaces of the strap adherend and the adhesive in a single lap joint. Three-dimensional nonlinear finite element analysis of adhesively bonded single lap joints made with high strength steel adherends under uniformly applied extension have been carried out. The interfacial stresses and strain energy release rate values, being indicative parameters, in the growth of the adhesion failures are computed in the vicinity of the pre-existing circular adhesion failure fronts when the load on single lap joint increases till failure. The magnitudes of the strain energy release rate are computed using the virtual crack closure technique. The results show that the sizes of the adhesion failure significantly influence the magnitudes of the interfacial stresses, the three modes of strain energy release rates and the load-bearing capacity of the single lap joint. The finite element analysis predicts that pre-embedded circular adhesion failures will not have grown from the pre-embedded circular adhesion failure front, instead the failure will be initiated from the overlap ends upon loading for the adhesive bonded single lap joint made with strong adherends and AV119 adhesive. The finite element analysis also proposes a method to calculate the strength of this type of joint configurations using the global shear strength of the adhesive and the intact bonded area. The finite element analysis predicted failure strength of the single lap joint is in good agreement with the experimentally obtained strength for the single lap joint containing pre-existing circular adhesion failure.

2023

A detailed 3D finite element model incorporating geometric, material and friction-based full contact nonlinearities is developed in this paper to numerically investigate the temperature effects on the stiffness of a hybrid metal-composite countersunk bolted joint. To validate the temperature effects on the joint stiffness, experiments were conducted using an Instron testing machine coupled to a temperature-controlled chamber. Experimental tests reveal that at negative temperatures the axial stiffness remains about the same and decreases with the increase of temperature. In numerical simulations the axial stiffness decreases gradually with the increase of temperature.

2023, Composite Structures

The present paper reviews the novel area of composite to composite and composite to metal joining, utilizing novel 3D reinforcement technology. The 3D reinforcement pinned technology extends the use of micro-pins from through-the-thickness laminate reinforcement to joints, while introducing AM (Additive Manufacture) and CMT (Cold Metal Transfer) technologies to the joint research field. The great advantages that this novel joining technique provides are lightweight connection, increased strength and significant improvement in damage tolerance. However, the concept has not been extensively explored in all loading nor environmental conditions and on the effects of the various design and manufacturing parameters.

2023, Journal of Composites Science

Large composite structures manufactured out-of-autoclave require the assembly and bonding of multiple parts. A one-shot cure manufacturing method is demonstrated using powder epoxy. Lap shear plates were manufactured from powder epoxy and glass fiber-reinforced plastic with four different bonding cases were assessed: secondary bonding using standard adhesive film, secondary bonding using powder epoxy, co-curing, and co-curing plus a novel Z-pinning method. This work investigates the lap shear strength of the four cases in accordance with ISO 4587:2003. Damage mechanisms and fracture behavior were explored using digital image correlation (DIC) and scanning electron microscopy (SEM), respectively. VTFA400 adhesive had a load at break 24.8% lower than secondary bonding using powder epoxy. Co-curing increased the load at break by 7.8% compared to powder epoxy secondary bonding, with the co-cured and pinned joint resulting in a 45.4% increase. In the co-cured and co-cured plus pinned cas...

2023, International Journal of Adhesion and Adhesives

Conventional single-lap adhesive joints between identical adherends achieve ultimate strength only after significant inelastic deformation of the adhesive and perhaps also the adherends. However purely elastic analysis provides insights and is relevant to fatigue initiation or brittle failure. We extend classical beam-based elastic results, both 'within the bond' (deriving more-accurate peak peel stress from the joint-edge moment) and 'beyond the bond' (determining the edge moment from adherend dimensions, remote boundary conditions, and load). Within the bond, we show that peak adhesive equivalent stress and principal stress are minimized when the bond length exceeds four characteristic lengths of the elastic-foundation shear stress equation. This makes simplified 'long' joint formulas attractive for initial design. We then examine how well the long-joint predicted peak peel stress matches plane strain finite element analysis, and empirically capture a peel-stress end effect due to nonzero adhesive Poisson ratio. With this end-effect correction, the limit of useful accuracy can be expressed as a ratio R a of (adherend axial stiffness) to (adhesive axial stiffness) being > a number of order 10 2-10 3 depending on Poisson ratio. This limit supplements the Goland and Reissner proposed applicability limit for elastic foundation analysis, expressed as a limiting ratio R v of through-thickness or vertical stiffnesses. Outside the bond, Timoshenko-style beam-column expressions are used to derive a simplified joint-edge moment factor. While similar in spirit to the edge-moment determination of Goland and Reissner for infinitelength pinned adherends, treating the bond region as a rigid block leads to simpler nonlinear expressions, and captures the moment-reducing benefits of shorter (finite-length) adherends and fixed-slope end conditions. Joint rotation effects become dominant when TL EI > 2 (L is adherend free length, T is tensile load), then joint rotation magnitude depends on TD EI / 2 (D is lap length).

2023

This is the age of technological revolutions. For newer mechanisms, advancement in bonding procedures is desperately needed. The most famous bonding type is Adhesive bonding. Double lap joints are considered as a good category joint in many applications. This paper explains the investigation on double lap hybrid joint. This was done for the vertical loaded MS Steel specimens. Overlapping length was kept constant and equal to 400 mm and two other factors viz. Number of rivets and adhesive composition (Resin to Hardner ratio) were varied. Finite Element analysis is done by using Ansys to see the nature of changes in the joint. Further validation by Mechanical testing is done by using Universal Testing Machine for Max. Stresses induced. Load- Stress relation obtained by Ansys results is approximately closer to experimental results. https://journalnx.com/journal-article/20150239

2023, Aerospace

Single shear or single lap joints are the most prevalent type of adhesive joints used in advanced engineering applications, where they are exposed to fatigue loadings in their services. Although their mechanical performances under static loading have been investigated extensively, the studies related to the fatigue performances were limited. For that purpose, single lap joints’ (SLJs) reaction to fatigue tensile loading was studied by varying the adherend thickness (3 mm to 6 mm) and fatigue load (3250 N to 1500 N). ABAQUS/Standard was used to create its advanced FE model. To represent the progressive damage in the adhesive layer, the fatigue damage model via the Paris Law, which links the rate of the crack expansion to the strain energy release rate (SERR), was integrated into the cohesive zone model with bi-linear traction–separation characteristics. The model was written in a UMAT subroutine. The developed model was validated using experimental data from the literature. The crack...

2023, Polymer Composites

There are many different techniques to improve the adhesion between carbon fiber-reinforced plastics (CFRP) which are used in aircraft primary structures. One of the most common techniques is the specific surface structuring of the joining parts in order to obtain mechanical interlocking. In this study, laser-induced surface structuring effect on adhesion strength of CFRP/CFRP joints was investigated by single lap shear tests. Microholes were created by CO 2 laser with different configurations in x and y axis for the best mechanical interlocking effect on adhesive bonding. The effects of microhole numbers (309, 625, and 914) and microhole formations (triangle, inverted triangle, frame, and box) on the adhesive bonding strength of the CFRP/CFRP joints were determined by using single lap shear tests according to ASTM D5868-01 standard with 60 kN DAR-TEC universal test machine. Single lap shear tests showed that microhole structuring has a significant effect on mechanical interlocking for adhesive bonding of CFRP/CFRP joints. Results showed that the shear strength of CFRP/CFRP joints improved at 309 microholes and frame type microhole formations. After mechanical tests, damage mechanisms were observed by using the optical microscope. POLYM. COMPOS., 2018.

2023, Polymer Composites

Adhesion can be greatly improved by the correct surface preparation techniques. One of the most common and useful technique is specific surface structuring which leads to mechanical interlocking and greater adhesion. This work describes the effect of laser-induced line pattern surface structuring on the mechanical interlocking mechanism and so on the adhesive bonding of carbon fiber reinforced polymer (CFRP) composites. Surface patterns with different laser scribes were obtained by CO 2 laser treatment. The effect of the number of a laser shot, the scribe depth, the number of the scribe and the angle between the direction of the laser scribes and mechanical test direction on the adhesive bonding strength of CFRP/CFRP joints was investigated by performing the single lap shear tests according to the ASTM D5868-01. After destructive tests, damaged surfaces were analyzed for determining the failure mechanisms. Mechanical tests showed that laser scribe characteristics especially the number of laser shot and the number of scribes have significant effects on the mechanical interlocking mechanism and so on the adhesion bonding strength. It is suggested that in order to improve the adhesion strength of CFRP/CFRP joints, mechanical interlocking mechanism shall be obtained by optimized laser scribe patterns. POLYM. COMPOS.

2023, Composites Science and Technology

Adhesively bonded composite-composite single-lap joints, with cross-ply GFRP adherends, have been cyclically loaded to initiate disbonding at either end of the overlap length. Disbond initiation and growth have been monitored using a combination of in situ photography (the joint is transparent) and a single chirped fibre Bragg grating (CFBG) sensor embedded within one composite adherend (with the low-wavelength end of the sensor adjacent to the cut end) and not in the adhesive bondline. Sensors having the same spectral bandwidth (20 nm), and lengths in the range 15 mm to 60 mm have been tested. The experimental results have been modelled using a combination of finite-element analysis and commercial software for predicting FBG spectra, and the predictions are in very good agreement with the experimental results. In all cases, it has been shown that the position of the disbond front can be located using the CFBG sensors with a precision of about 2 mm.

2023, Composites Science and Technology

Structures made of carbon fiber-reinforced polymer (CFRP) can be assembled using adhesive bonding. However, such bonding is prone to brittle delamination, and a method to improve delamination resistance is desirable. Here, we propose a technique to introduce crack-arrest features that increase the R-curve response by engineering the adhesive bondline/interface. We specifically designed a wavy net-like thermoplastic insert that was embedded into the thermoset adhesive bondline where the new mechanisms of energy dissipation were generated. We demonstrate that the technique is effective at improving mode I fracture toughness of secondary bonded carbon/ epoxy by more than 400%. The hybrid thermoset/thermoplastic bondline architecture was carefully tailored to achieve its best performance. We demonstrate that introducing porosities in the adhesive bondline (by adding a limited amount of thermoset adhesive) further improves the fracture toughness. This toughness improvement originates from the extrinsic toughening of the crack-arrest feature, which is enabled by the insert ductility and microstructures (via strand formation, anchoring and stretching).

2023, Elsevier

Fiber Reinforced Plastics (FRPs) are being used extensively in various engineering applications ranging from aerospace to sports goods. In recent years, environmental concerns and awareness have challenged engineers and scientists to develop materials that are sustainable and have the potential to replace the traditional FRPs. Natural fiber-based polymeric composites (NFRPC) are now being investigated and proposed worldwide for various applications, especially automotive components and domestic products. To ensure the fabrication of highly intricate composite products, joining becomes inevitable. Adhesive joining is the most commonly employed fabrication process for composite joints. However, the performance of adhesive joints is susceptible to their exposure to different environmental conditions. In the present experimental investigation, the joint strength of woven fiber mat (sisal, jute, and hybrid) reinforced epoxy composites has been investigated in Three Months Cyclic Temperature Variation, and the natural fiber reinforced epoxy adherends have been successfully joined using adhesive along with two/four holes in the overlap area. The performance of the adhesive joints has been investigated under a daily thermal cycle from 5 • C (12 hrs.) to 40 • C (12 hrs.), for three consecutive months. It was observed that the hybrid composites recorded better-joining performance. Moreover, the Field Emission Scanning Electron Microscopy (FE-SEM) has been used to understand the failure mechanisms during tensile testing of adhesively bonded natural fiber-reinforced composite laminates. It has been found that the exposure of the composite joints to a variable temperature during the day has a significant effect on their tensile behavior. The major factors affecting the performance of joints exposed to the thermal cycle are; the type of natural fiber, the number of holes in the adherend area, and the duration of exposure. The results are important for the designers of composite structures with adhesively bonded joints.