Performance Of Single-lap Joints Research Articles

Experimental and numerical study on mechanical behavior of 3D printed adhesive joints with polycarbonate substrates

AbstractAdhesive joints play a crucial role in enhancing the structural integrity and performance of 3D printed parts. The purpose of this study is to investigate the failure load and behavior of polycarbonate (PC) single lap joints (SLJs) produced by fused deposition modeling (FDM) using experimental and finite element analysis (FEA) methods. The FEA of joints presents a new approach by integrating PC substrates with Hill yield criterion, transversely isotropic material and adhesive layer with cohesive zone modeling (CZM). The study focused on the effect of printing angles (0°, 45°, and 90°) and overlap lengths (12.5 and 25 mm) on the performance of SLJs. The influence of 3D printing parameters on the mechanical behavior of PC joints was investigated by tensile testing of SLJs. The experimental failure load was 1586 N for a 12.5 mm joint at 90° and 4115 N for a 25.4 mm joint at 0°. Comparison of the experimental and FEA failure loads of the joints showed maximum and minimum differences of 11.98% and 1.34%, respectively. This result showed that the proposed model is applicable for determining the joint strength as a function of the printing angle and monitoring the joint damage behavior.

Long‐term performance of single‐lap joints: Review, challenges and prospects in civil engineering

AbstractCompared with traditional technology, bonding technology is more suitable for civil structure reinforcement because of its cost‐efficiency and superior mechanical properties. However, research on the long‐term performance of single‐lap joints (SLJs) requires better organization and comprehension. This article aims to investigate the long‐term performance and optimization design of SLJs. The main factors influencing the long‐term performance of SLJs from both material and component levels are discussed. The moisture diffusion mechanisms of bulk adhesives and the degradation mechanisms of SLJs are explored. Moreover, the optimization design of SLJs focuses on evaluating the overlap length, adhesive layer thicknesses, and changes in adhesives along the overlap length based on available literature. It is found that the applicability of diffusion models should be validated, and the selection of the models should consider working environments and types of adhesives. Exploring failure mechanisms and design criteria for the mixed SLJs in hygrothermal environments with/without sustained or alternating load is significant for the optimization design. This article indicates the limitations on the shear strength and long‐term performance of SLJs in available studies and provides insights into the challenges and prospects of their optimization design.

The W-Zn-Co-Y2O3 alloys synthesized by a secondary ball milling method and their effects on adhesion performance of single lap joints of aluminum composites

W-Zn-Co-Y2O3 tungsten heavy alloys were produced using a two-step mechanical milling method. In the first step, Zn-Co raw materials were milled for 24 h. Then, in the second stage, the Zn-Co compounds obtained were mechanically milled with tungsten (W) and yttrium(III) oxide (Y2O3). This study compared the new W-Zn-Co-Y2O3 alloy, obtained through two-stage mechanical alloying, with the same alloy produced using classical mechanical milling. The aim was to investigate and compare their structural, morphological, and mechanical properties. Yttrium oxide was used to promote the formation of in-situ oxide dispersoids during mechanical alloying. Oxide dispersion-strengthened tungsten heavy alloys are known for their exceptional mechanical properties, making them suitable for various high-temperature applications. The structures were analyzed using XRD, crystallite size, TEM, SEM, and EDX techniques. The microstrain of the final alloys was calculated as 15.79 × 10−3 and 13.12 × 10−3 for the classically obtained alloy and secondary milled alloys after 24 h of milling, respectively. Additionally, the reinforcing effects of the produced alloy on single-lap joints of aluminum composites were investigated. The results demonstrated that the tungsten alloy produced using the secondary ball method exhibited better mechanical performance.

MWCNT and nano-silica hybrids effect on mechanical and fracture characterization of single lap joints of GFRP plates

The current study aimed to explore the effects of nanoparticle hybridization on the shear and flexural performance of single lap joints (SLJs) of glass fiber reinforced polymer (GFRP) substrates. To this end, the hybridizations of multi-walled carbon nanotubes (MWCNT) and silica nanoparticles at various concentration rates were incorporated into the epoxy adhesive. Three-point bending tests and single-lap shear tests were performed to analyze in detail the effects of hybrid nanoparticle inclusions on adhesion performance under different loads. The maximum values for both shear and flexural strengths were achieved from the samples containing the combination of 0.5 wt.% MWCNT and 0.25 wt.% Nano-silica particles. The enhancements in shear strength and flexural strength were 45.4% and 63.2%, respectively, compared to pure samples. Furthermore, damage surfaces were examined via scanning electron microscopy (SEM) to investigate fracture mechanisms and failure modes. The findings demonstrated that almost all nanoparticle-doped samples, regardless of hybrid or single nanoparticle, exhibited higher load-bearing capability by increasing the adhesion ability of the additive and the adhesive. It was observed that the failure mechanisms such as crack deviation, crack pinning, pull out, bridging, etc. occurred in the nanoparticle doped adhesive joints as seen in SEM images.

Fatigue performance of single lap joints with CFRP and aluminium substrates prior and after hygrothermal aging

AbstractAdhesive bonding has been extensively used to join composites and aluminium alloys in the automotive industry, but a deeper understanding of its fatigue behaviour is still required. This work presents a novel evaluation of the combined performance of joints manufactured with carbon fibre reinforced plastic (CFRP) and aluminium substrates subjected to fatigue loads in the unaged, hygrothermally aged, and dried after hygrothermal aging states. The experimental results allowed to conclude that the fatigue performance of joints can be affected by changes induced by the drying process or losses in the interface strength and that dissimilar combination of substrates sustains higher number of cycles to failure. The fatigue performance of joints with dissimilar substrates was found to be better than that of joints with similar substrates, which can be attributed to the lower stresses acting on the adhesive layer. The presence of water has also noticeably changed the fatigue performance of joints with dissimilar substrates.

Effect of adhesive thickness and overlap on the behavior of composite single-lap joints

The effect of adhesive thickness and adherent overlap on behavior of composite single-lap joints (SLJ) under tensile load is studied by using a 3D finite-element model. A bilinear Cohesive Zone Model (CZM) law is used to represent the adhesive behavior and its parameters are determined as a function of adhesive thickness by carrying out Double Cantilever Beam and End-Notched Flexure tests. The performance of SLJ is defined by peak load, maximum shear, and peel stresses. For the range of adhesive thicknesses considered, both maximum shear and peel stresses decrease with increasing adhesive thickness, while they increase with increasing overlap length.

Fatigue Performance of Friction Stir Weld-Bonded Al-Mg joints

The need for weight reduction and leaner manufacturing and assembly processes in aircraft construction has led to the pursuit of alternative joining processes to conventional riveting. One such technology that has been considered for this application is friction stir welding (FSW). Since it is a solid-state joining method, it results in high performing joints in a wide range of materials while avoiding overlap lengths and added weight from fasteners, crack stoppers, doublers, etc. However, the adoption of this technology to the assembly of large fuselage shell components is challenging, due to geometric tolerance management requirements. A hybrid friction stir weld-bonding method combining overlap friction stir welding and adhesive bonding (AB) has been proposed as an alternative, aims to incorporate properties and characteristics of both joining technologies, as well as improving damage tolerance. Fatigue performance of single lap joints of AA6082-T6 Al-Mg alloy was assessed and benchmarked against FSW overlap and hybrid friction stir weld-bonding joints. Significant strength and ductility increase were achieved through the hybridization of the overlap FSW joints. Fatigue strength of the hybrid joints was also higher than FSW overlap joints.

Effect of nanoclay and bolt preloads on the strength of bolted joints in glass epoxy nanocomposites

The present work deals with the effect of different molding parameters and bolt pretension on the performance of single-lap joints. Bolt joints were prepared from woven glass fiber reinforced laminates incorporating nanoclay content which was varied from 0 to 5 wt%. Curing parameters for the nanocomposite manufacturing were optimized using the Taguchi method. Different geometric parameters, i.e., edge distance-to-hole diameter (E/D) ratio and width-to-hole diameter (W/D) ratio, were varied over the range of 2–5. To analyze the effect of bolt preloads, different levels of preloads, i.e., 0, 3, and 5 Nm, were considered for the failure analysis of the joint. Progressive damage analysis along with the characteristic curve method and Hashin failure criteria was performed to predict the failure load and failure modes in the bolted joints, numerically. Failure load was improved by 19 and 37% for joints with 3 and 5 Nm torque, respectively.

Three-Dimensional Modeling of Single-Lap Joints with Variable Interfacial Crack Length <sup></sup>

This paper investigated the performance of single-lap joints with interfacial crack through the finite element method. The finite element method was validated by the G-R solutions at first. And then the influence of geometric parameter of the joint as well as the length of the interfacial crack were discussed. Results showed that the presence of a spew fillet can reduced the stress intensity factors (SIF).The relationship of the crack length ratio and SIF, adhesive thickness ratio and SIF were built.

Influence of process parameters on mechanical performance and bonding area of AA2024/carbon-fiber-reinforced poly(phenylene sulfide) friction spot single lap joints

Abstract The effects of friction spot joining process parameters on the bonding area and mechanical performance of single lap joints were investigated using full-factorial design of experiments and analysis of variance. On one hand, the main process parameters with significant influence on the bonding area were joining pressure, tool rotational speed and joining time. On the other hand, tool rotational speed and joining pressure displayed the highest influence on the lap shear strength of the joints followed by tool plunge depth, whereas the joining time was not statistically significant. The interaction between the rotational speed and joining time was the only interaction with a significant effect on the mechanical performance. Joints with ultimate lap shear forces varying between 1698 ± 92 N and 2310 ± 155 N were obtained. It was observed that generally a larger bonding area as a result of higher heat input leads to an increased mechanical performance of the joints. The generated regression model by the analysis of variance was used to identify an optimized set of parameters for increasing the lap shear strength of the joints to 2280 ± 88 N. Furthermore, the process temperature was monitored, which varied in the range of 370–474 °C.

Solutions for Clamped Adhesively Bonded Single Lap Joint With Movement of Support End and Its Application to a Carbon Nanotube Junction in Tension

This article presents analytical solutions for a clamped-clamped adhesively bonded single lap joint with movement of supports and its application to studying the failure mechanism of carbon nanotube junctions in a tensile test. In the analytical model, the interface shear and normal stresses, movement of one support end, geometric nonlinearity, and the contact stresses between two cylinders are considered. Analytical solutions are derived for a clamped-clamped single lap joint with movement of one support end first, and then geometrically nonlinear finite element analysis is conducted to verify the present analytical solutions. An equivalent two-dimensional model is presented for a junction self-assembled by two carbon nanotubes, and the failure mechanism of the carbon nanotube junction is then studied by using the present analytical solutions. Structural performance of single lap joints with movement of support ends as boundary conditions is also investigated.

Adhesively bonded single lap joints with non-flat interfaces

A series of experiments and detailed finite element simulations were carried out to study the performance of single lap joints with non-flat interfaces loaded at a small angle to the mean bond plane. In the experimental part, fiber reinforced epoxy composite adherends with sinusoidal bonding surfaces (but no change to the exterior sample dimensions) were fabricated in a purpose-built mold. This construction method allowed the fibers to follow the sinusoidal profile for maximum strength. Then the sinusoidal surfaces were joined by a controlled-thickness layer of epoxy. Single lap joints with a flat interface were also fabricated using the same composite material and with the same overall shape. The experiments showed that the interface non-flatness has significant effect on the mechanical behavior and strength of the bonded joints. Finite element simulations of a simplified two-dimensional model with isotropic adherends were also carried out to estimate the distribution of shear and peeling stresses along the bonded joints, and the results were related to the experimental observations. Parametric variations were studied via FEA to highlight the role of interface shape, adhesive elastic modulus and a central void size on the distribution of stresses, and inherently the overall strength and behavior of the bonded joints.

Numerical Analysis of Co-Cured Composite Single Lap Joint with Spew Fillets

Spew fillet is common in co-cured composite single lap joint. It plays an important role in the safety of the joint. But few attentions were paid to the subject in former investigations. In this paper, co-cured composite single lap joints with spew fillets under static tensile load were investigated numerically using the commercial finite element code ANSYS. The submodeling technique was employed to overcome the problem caused by extra aspect ratio of elements. The computation results indicated that the existence of spew fillets will not change the possible failure location, but will improve the anti-failure performance of single lap joint.

Effect of Z-pins' diameter, spacing and overlap length on connecting performance of CMC single lap joint

The effect of through-thickness reinforcement by composite pins (Z-pins) on the static tensile strength and failure mechanisms of the joints made from ceramic matrix composite (CMC) is investigated. Overlap length of the single lap joint is 15 mm, 20 mm, 23 mm, 37 mm, and 60 mm, respectively. The experimental results indicate that the final failure modes of the joints can be divided into two groups, (a) the bond-line stops debonding until crack encounters Z-pins; and then the adherends break at the location of Z-pins, when overlap length is more than 20 mm; (b) the bond-line detaches entirely and Z-pins are drawn from adherends, when overlap length is equal to 15 mm. A simple efficient computational approach is presented for analyzing the benefit of through-thickness pins for restricting failure in the single lap joints. Here, the mechanics problem is simplified by representing the effect of the pins by tractions acting on the fracture surfaces of the cracked bond-line. The tractions are prescribed as functions of the crack displacement, which are available in simple forms that summarize the complex deformations to a reasonable accuracy. The resulting model can be used to track the evolution of complete failure mechanisms, for example, bond-line initial delamination and ultimate failure associated with Z-pin pullout, ultimate failure of the adherends. The paper simulates connecting performance of the single lap joints with different Z-pins' diameter, spacing and overlap length; the numerical results agree with the experimental results; the numerical results indicate enlarging diameter and decreasing spacing of Z-pins are in favor of improving the connecting performance of the joints. By numerical analysis method, the critical overlap length that lies between two final failure modes is between 18 mm and 19 mm, when Z-pins' diameter and spacing are 0.4 mm, 5 mm, respectively.