Results Of Lap Shear Tests Research Articles

Laser heat conduction joining of polycarbonate and aluminum alloy

The present work demonstrates the laser heat conduction joining (LHCJ) of polycarbonate and aluminum alloy. The experiments are performed to examine the impact of scan speed and laser power on the joint’s strength and quality. The bonding between the substrates was assessed by examining the cross-section using a scanning electron microscope and conducting energy-dispersive X-ray spectroscopy. The fractured surfaces are inspected by an optical microscope to explore the bond morphology. A finite-element-based numerical model is developed for the estimation of interface temperature and validated with the experimental results. Results of lap shear tests show that the weld strength is significantly affected by the laser power, scan speed, interface temperature, and bubble area. Microscopic observations of the joint interface disclose bubble area and mechanical interlocking between polycarbonate and aluminum. Through X-ray photoelectron spectroscopy (XPS) analysis, it was discovered that the interface experiences chemical bonding facilitated by the formation of Al-O-C bonds, which effectively enhances the strength of the joint.

Depriving friction stir weld defects in dissimilar aluminum lap joints

The contemporary automotive industry increasingly incorporates composite materials and innovative joining techniques to meet customer demands for lightweight, high-strength alloys. This research explores the feasibility of using friction stir welding (FSW) methods to fabricate dissimilar aluminum nanocomposite lap joints, integrating Al2O3 nanoparticles into the weld nugget. Lap joints were prepared with varying tool rotation speeds (1000–1600 rpm) and the mechanical and metallurgical behaviors of AA6061–AA7075-T6/Al2O3 lap joints were examined. The inclusion of filler material in the weld joint resulted in an 18% increase in shear strength compared to joints without filler. Dynamic crystallization impeded grain boundaries and reduced grain size in the weld stir zone (SZ), with the most enhanced mechanical characteristics observed at a tool rotation speed of 1400 rpm. The shear strength at 1400 rpm was 5780 N, representing a 17% increase compared to joints prepared at 1000 rpm. Field emission scanning electron microscopic examination revealed evenly dispersed Al2O3 nanoparticles within the weld zone, supporting the lap shear test results. Notably, joints created at lower (1000 rpm) and higher tool rotational speeds (1600 rpm) exhibited brittle fracture behavior. The addition of Al2O3 significantly improved lap joint tensile strength due to its uniform dispersion in the SZ. Increasing the FSW tool rotational speed from 1000 to 1400 rpm facilitated nanoparticle dispersion, further enhancing lap joint strength.

Enhanced interfacial bonding strength in K-300 adhesive joint between aluminum alloy and mild steel substrates through effective resin precoating treatment

In this work, two different surface treatments, such as grinding and acid-pickling, were applied to both mild steel and aluminum alloy substrates for performance comparison. A novel method known as resin precoating (RPC) has been used effectively to seal the micro-cavities surface and enhance substrate wetting. The RPC solution consists of 10 % resin, and 90 % acetone (without hardener) is applied onto the grinding and acid-pickling metal substrate. The acetone solution facilitates resin penetration into the micro-cavities formed through grinding and acid pickling. It enables effective coating and wetting of micro-debris, ultimately eliminating micro-voids or gaps between the metal substrate and the adhesive joint. Then, the standard K-300 adhesive (with hardener) is applied to the metal substrate surface. The adhesive bonding strength was determined using a single-lap shear test on varied surface conditions. The topography of surface-treated samples was analyzed using X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and Contact Angle Goniometer. The grinding and acid-picking surface treatment increased the surface roughness of the substrate, which reduced the contact angle and improved the mechanical interlocking effect. The single lap shear test results show that the bonding strength of the grinded samples was superior to that of the acid-pickled samples. The RPC treatment further enhanced the bonding strength of all the grinded samples by 16.83–19.77 % and for acid-pickled samples by 20.79–44.97 %, which is higher than the values observed without RPC treatment. The combination of grinding and RPC surface-treated samples exhibited a superior bonding strength of 14.05 MPa. This value was 12.38 % greater than the bond strengths of acid-pickled samples, and the failure mode shifted from adhesive to cohesive failure mode. Thus, RPC treatment enhanced the wettability of metal substrates and maximized the utilization of contact areas on roughened substrate surfaces, consequently improving adhesive bond strength. These grinding and acid-pickling surface treatments are effective and well-suited for aerospace, automobile, and aviation applications.

Constructing quasi-vertical carbon nanotubes fiber bridging on aluminum alloy with micro-channels to improve adhesive bonding with carbon fiber reinforced polymer composites

The poor wettability and compatibility, and weak mechanical interaction of bonding interface are main concerns for adhesive bonding of aluminum (Al) alloy and carbon fiber reinforced polymer (CFRP) composite, limiting its high strength developing and industrialization. In this study, the united treatments of anodizing, chemical vapor deposition (CVD) and resin pre-coating (RPC) were adopted to construct the quasi-vertically distributed carbon nanotube (CNT) fiber bridging for reinforcing the adhesive bonding joints. The results exhibited that better surface properties including morphology, roughness and wettability were obtained after anodizing. CNTs could be in-situ grown via the novel CVD method in the channels or micro-cavities formed by anodizing treatment. Acetone-diluted epoxy resin solution enabled to flow into the root of micro-cavities or the gap of growing CNT fibers to reduce potential void defects. Single lap shear test results indicated that Al-CFRP composites treated by anodizing, CVD and RPC performed up to 136.1 % increment in strength compared to the base. While the original debonding failure on Al alloy surface was changed into the complete delamination failure of CFRP composites, verifying the stronger bonding interface and strength. Thus, the novel united treatments were effective and might be an alternative solution in developing high-performance Al-CFRP composites.

A novel epoxy adhesive with metal organic framework (MOF) and poly(butyl acrylate‐block‐styrene) for bonding aluminum–aluminum joints: A complete overview of mechanical, thermal, and morphological properties

AbstractIn this study, MIL‐101 (Cr) and NH2‐MIL‐101 (Cr) nanoparticles were synthesized by hydrothermal method. Butyl acrylate‐styrene copolymer was used along with these nanoparticles to improve the mechanical properties of epoxy adhesive. The results of the Fourier Transform Infrared (FTIR) and X‐ray diffraction (XRD) test showed that the synthesis and functionalization of the metal organic framework (MOFs) were successful. The mechanical properties and adhesion features in the lap joint bonding of aluminum foil to the aluminum foil of modified epoxy adhesives were investigated by tensile and lap shear tests. The results of the tensile test showed that by adding 0.3 wt% of NH2‐MIL‐101 (Cr) and 2.5 wt% of poly(butyl acrylate‐block‐styrene) to epoxy adhesive, the tensile strength, modulus and toughness of dumbbell samples were increased up to 34.46%, 31.74% and 58.53%, respectively. Furthermore, based on the lap shear test results, by adding 0.3 wt% NH2‐MIL‐101 (Cr) along with 2.5% poly(butyl acrylate‐block‐styrene) to the epoxy adhesive, the lap shear strength of samples increased from 1.05 ± 0.08 MPa to 5.25 ± 0.06 MPa compared to the neat epoxy adhesive. According to the TGA test, the highest thermal stability is related to the sample containing 0.3 wt% of NH2‐MIL‐101 nanoparticles and 2.5 wt% of the copolymer. The image of the fracture surface of the sample containing 0.3 wt%. NH2‐MIL‐101 (Cr) and 2.5 wt% block copolymer shows that the interface of nanoparticles and the matrix improved due to the chemical reaction of functional groups of nanoparticles and adhesive matrix.

Enhancing adhesive bond strength of CFRP/titanium joints through NaOH anodising and resin pre-coating treatments with optimised anodising conditions

Adhesively Bonded Carbon Fibre Reinforced Plastic (CFRP) and titanium alloy have been extensively used as a hybrid structure in modern aircrafts due to their excellent combination of mechanical properties and chemical stabilities. This study utilised NaOH anodising method to create micro-rough titanium surfaces for enhancing adhesive bonding between titanium alloy and CFRP laminates. A special and simple technique named Resin Pre-Coating (RPC) was also employed to improve the surface wetting of anodised titanium and grinded CFRP substrates. The influences of anodising temperature and duration on the surface morphology, wettability and adhesive bond strength were investigated. The single lap shear test results showed that the bond strength of specimens anodised at 20 °C for 15 min improved by 135.9% and 95.4%, respectively, in comparison with that of acid pickled and grinded specimens (without RPC treatment). Although increasing the anodising temperature and duration produced rougher titanium surfaces, the adhesively bonded joints were not strong enough due to relatively friable titanium oxide layers.

Simultaneous improvement of heating efficiency and mechanical strength of a self-healing thermoplastic polymer by hybridizing magnetic particles with conductive fibres

Radio-Frequency (RF) induction heating is a versatile in-situ method for contactless heating of structures by utilizing either magnetic hysteresis loss or eddy-current loss mechanism. Achieving high heating efficiency without degrading mechanical properties is a major challenge. Herein, a RF induction compatible self-healing composite was developed by hybridizing iron oxides (Fe3O4) nanoparticles with carbon fibre veils (CFVs) in poly(ethylene-co-methacrylic acid) (EMAA), which could possess both high magnetic and electrical properties. Owing to the multiscale conductive networks built by Fe3O4 nanoparticles and CFVs, the electrical conductivity of the nanocomposite was found to be higher than the linear combination of the individual contributions, thus creating a synergistic improvement in electrical conductivity and heating efficiency. Furthermore, single lap shear test results demonstrated that the combination of Fe3O4 nanoparticles and CFVs could significantly improve the bonding strength of EMAA polymer. Therefore, the hybridization of magnetic particles with conductive fibres offers a promising technology for a wide range of applications, such as self-healing, reversable bonding, and multiple use bonded composites.

Influence of Maleinized Polybutadiene on Adhesive Strength and Toughness of Epoxy Resins

This study explored the effect of maleinized polybutadiene (MPB) on the mechanical properties of epoxy resins. Diglycidyl ether of bisphenol-A, an epoxy resin, was modified by incorporating MPB having different molecular weights in order to improve the fracture toughness and peel strength. MPB was mixed with epoxy resin at several concentrations (5, 10, and 15 phr), with the epoxy resin as the major phase and MPB as the minor phase. A comparative study was performed to investigate the influence of MPB on epoxy resins based on their molecular weight difference. Lap shear test results showed that the shear strength of the MPB-modified epoxy resins was superior to that of the neat epoxy resin. At 10 wt% MPB loading, the modified epoxy resin exhibited an 87% enhancement in T-peel strength relative to that of the neat epoxy resin. Moreover, the fracture energy of the modified epoxy system increased proportionally with the amount of MPB in the epoxy matrix. These results indicate that MPB incorporation is a simple and effective method for designing multifunctional epoxy resins, thus facilitating their industrial application in various spheres.

Performance and failure assessment of adhesively bonded non-crimp fabric carbon fiber/epoxy composite single lap joints

Carbon fiber-reinforced plastic (CFRP) composite materials have experienced increased use for load-bearing structures in automobiles owing to their high specific mechanical properties. However, critical to widespread adoption of CFRPs are the development of robust joining methods with appropriate surface preparation to maximize joint strength, as well as an improved understanding of failure mechanisms to enable computational modeling for supporting design. In the present study, an adhesively bonded non-crimp fabric CFRP single lap joint (SLJ) was investigated to quantify the effect of the composite adherend surface treatment and stacking sequence on the lap shear strength, and to assess the corresponding failure mechanisms. Single lap shear test results revealed that the highest lap shear strength was achieved by abrading the surface with sandpaper, relative to an unprepared surface or one treated by grit blasting. Similarly, an adherend with a higher effective flexural longitudinal modulus, achieved through stacking sequence, increased the lap shear strength owing to reduced Mode I loading on the adhesive joint. Distinct failure processes were observed for CFRP adherends with different stacking sequences, where the locations of intra-ply and inter-ply cracks varied as a result of variations in the in-plane and out-of-plane stresses. Notwithstanding, the final failure event for all SLJ specimens was failure of the thin layer of matrix in the 0° ply of the adherends. Three-dimensional finite element analyses of the SLJ specimens were employed to determine the local stress components driving the observed failure mechanisms within the plies of the CFRP adherends. The results of this study provide a recommended surface treatment to maximize adhesive joint strength for CFRP adherends, along with a comprehensive assessment of failure mechanisms, to inform the design and application of CFRP materials in lightweight structures.

A Numerical and Experimental Study of Adhesively-Bonded Polyethylene Pipelines.

Adhesive bonding of polyethylene gas pipelines is receiving increasing attention as a replacement for traditional electrofusion welding due to its potential to produce rapid and low-cost joints with structural integrity and pressure tight sealing. In this paper a mode-dependent cohesive zone model for the simulation of adhesively bonded medium density polyethylene (MDPE) pipeline joints is directly determined by following three consecutive steps. Firstly, the bulk stress-strain response of the MDPE adherend was obtained via tensile testing to provide a multi-linear numerical approximation to simulate the plastic deformation of the material. Secondly, the mechanical responses of double cantilever beam and end-notched flexure test specimens were utilised for the direct extraction of the energy release rate and cohesive strength of the adhesive in failure mode I and II. Finally, these material properties were used as inputs to develop a finite element model using a cohesive zone model with triangular shape traction separation law. The developed model was successfully validated against experimental tensile lap-shear test results and was able to accurately predict the strength of adhesively-bonded MPDE pipeline joints with a maximum variation of <3%.

Effects of coarse aggregate volume on CFRP-concrete bond strength and behavior

A major challenge in using fiber reinforced polymer (FRP) composites for repair and strengthening of concrete structures has been debonding of FRP from concrete substrate. It is, therefore, essential to identify the parameters involved in FRP-concrete bond behavior to predict the loading capacity of the bond and, thereby, possibly postpone the debonding of the strengthening sheet. One such important parameter is the coarse aggregate at the interface between the substrate concrete and the FRP sheet which becomes exposed after surface preparation of the concrete for adhering FRP sheets; the coarse aggregate might affect FRP-concrete bond behavior and strength. The present study was designed and implemented to investigate the effects of coarse aggregate volume on FRP-concrete bond strength and behavior. To achieve this objective, 52 concrete specimens were cast and strengthened with carbon FRP (CFRP) sheets 200 mm long and 50 mm wide using the externally-bonded reinforcement (EBR) technique. To better understand the effect of coarse aggregate, a parameter called “fine fraction” was defined as the ratio of fine aggregate to total concrete aggregate, with values in the range of zero to 1.0; zero for concrete mixes containing only coarse aggregate and 1.0 for those with only fine aggregate. The specimens thus prepared were then subjected to direct single lap-shear test. Particle image velocimetry (PIV) technique was also utilized to determine the displacement fields. The single lap-shear test results revealed that variations in fine fraction led to changes in bond strength such that fine fraction values of 0.3–0.6 led to reduced bond strength while those from 0.6 to 1.0 increased it. Comparison of experimental results obtained from the current study and those predicted by codes indicated the underestimation of bond strength by the codes in the absence of such surface parameters as fine fraction.

Shear strength and fracture surface analysis of Sn58Bi/Cu solder joints under a wide range of strain rates

The influences of the strain rate on the shear strength and failure mode of Sn58Bi/Cu solder joints were investigated. After reflowing, some Kirkendall voids were observed at the neighborhood of the Cu3Sn/Cu interface or in the inner Cu3Sn layer. In addition, another type of void could also be observed inside the Sn58Bi eutectic solders, and its size was much larger than that of Kirkendall voids. Some Bi particles were obviously found to segregate at the interface between the Cu-Sn IMC and the Sn58Bi solder. The single lap shear test results indicated that the strain rate had an important influence on the shear strength and failure mode of Sn58Bi/Cu solder joints. The shear strength of joints demonstrated increment at first and then decrement as the strain rate increased from 3.33 × 10−4 s−1 to 3.33 s−1. It was observed that all Sn58Bi/Cu solder joints broke in a mixed-type fracture mode under a wide range of strain rates. Additionally, more broken IMC grains were exposed on the fracture face and more fracture occurred within the IMC layer with increasing strain rate. Furthermore, the fracture path gradually moved from the solder side to the inner IMC side as the strain rate increased.

Improvement in Adhesive Performance of Single-Lap Joining Composite Lamınates by Using Nano-Montmorillonite Modified Epoxy

Nanoparticles have been widely used as reinforcing materials related to polymer matrices for outstanding performance. In this paper expresses modified epoxy adhesives which are enhanced conventional adhesives widely used in industry. In this study, nano-montmorillonite (nano-MMT) (1% to 5% by weight) was mixed into the epoxy resin by using ultrasonication to obtain toughened adhesives. Carbon fiber reinforced composites was used as adherent material and it’s were prepared according to ASTM D5868-01. It has been clearly revealed that the additions of low concentrations of nanosized particles (2 % by weight) performed higher mechanical strength than others and also show lower adhesive performance with increased nano-MMT weight percentage. According to the lap shear test results, shear strength was significantly increased with addition of 2wt% nano-MMT and the strengths of the joints were found to be 12.5% higher than neat epoxy adhesives.

Utilization of Cellulose Nanofibrils as a Binder for Particleboard Manufacture

Cellulose nanofibrils (CNF) were investigated as a binder in the formulation of particleboard (PB) panels. The panels were produced in four different groups of target densities with varying amounts of CNF binder. The produced panels were then tested to determine the modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), water absorption (WA), and thickness swelling (TS) properties. Density gradients through the thickness of the panels were evaluated using an X-ray density profiler. The effect of drying on the strength development and adhesion between CNF and wood particles (WP) was investigated, and the effect of surface roughness on the wood-CNF bonding strength was evaluated through lap shear testing and scanning electron microscopy. It was found that at lower panel densities, the produced samples met the minimum standard values recommended for particleboard panels. Medium-density panels met the standard levels for IB, but they did not reach the recommended values for MOR and MOE. The possible bonding mechanism and panel formation process are discussed in light of microscopic observations and the results of lap shear tests were presented.

Defect features, texture and mechanical properties of friction stir welded lap joints of 2A97 Al-Li alloy thin sheets

1.4mm 2A97 Al-Li alloy thin sheets were welded by friction stir lap welding using the stirring tools with different pin length at different rotational speeds. The influence of pin length and rotational speed on the defect features and mechanical properties of lap joints were investigated in detail. Microstructure observation shows that the hook defect geometry and size mainly varies with the pin length instead of the rotational speed. The size of hook defects on both the advancing side (AS) and the retreating side (RS) increased with increasing the pin length, leading to the effective sheet thickness decreased accordingly. Electron backscatter diffraction analysis reveals that the weld zones, especially the nugget zone (NZ), have the much lower texture intensity than the base metal. Some new texture components are formed in the thermo-mechanical affected zone (TMAZ) and the NZ of joint. Lap shear test results show that the failure load of joints generally decreases with increasing the pin length and the rotational speed. The joints failed during the lap shear tests at three locations: the lap interface, the RS of the top sheet and the AS of the bottom sheet. The fracture locations are mainly determined by the hook defects.

Miniaturization of Micro-Solder Bumps and Effect of IMC on Stress Distribution

As the joints become smaller in more advanced packages and devices, intermetallic (IMCs) volume ratio increases, which significantly impacts the overall mechanical behavior of joints. The existence of only a few grains of Sn (Tin) and IMC materials results in anisotropic elastic and plastic behavior which is not detectable using conventional finite element (FE) simulation with average properties for polycrystalline material. In this study, crystal plasticity finite element (CPFE) simulation is used to model the whole joint including copper, Sn solder and Cu6Sn5 IMC material. Experimental lap-shear test results for solder joints from the literature were used to validate the models. A comparative analysis between traditional FE, CPFE and experiments was conducted. The CPFE model was able to correlate the experiments more closely compared to traditional FE analysis because of its ability to capture micro-mechanical anisotropic behavior. Further analysis was conducted to evaluate the effect of IMC thickness on stress distribution in micro-bumps using a systematic numerical experiment with IMC thickness ranging from 0% to 80%. The analysis was conducted on micro-bumps with single crystal Sn and bicrystal Sn. The overall stress distribution and shear deformation changes as the IMC thickness increases. The model with higher IMC thickness shows a stiffer shear response, and provides a higher shear yield strength.

Effects of water immersion on the bond behavior between CFRP plates and concrete substrate

Effects of water immersion on the behavior of bond between CFRP plates and concrete substrate were experimentally investigated and analytically modeled. The finite element method was used to simulate the distribution of the moisture content in the interfacial zone. Single lap shear test results showed that water immersion decreases the maximum bond stress, bond capacity, and fracture energy as well as the maximum slip. Increasing the immersion time led to more moisture uptake in the adhesive layers, and more degradation of the bonding properties. The thickness of the adhesive layers (i.e., 0.2mm and 1mm) affects the bonding properties and the resistance to the water immersion. The thinner the adhesive layer, the higher moisture content is found at the adhesive/concrete interface. Water immersion altered the debonding mode from cohesive concrete fracture to adhesive separation from the concrete substrate, which was attributed to the weakening of the bonding strength between silica and epoxy adhesive due to moisture ingress.

Welding of Aluminum to DP600 Steel Plates by Refill Friction Stir Spot Welding Process (Refill FSSW): Preliminary Results

The main objective of the current work was to produce sound Refill FSSW joints between AA6181-T4 aluminum and DP600 steel plates. The steel plates were used in two different surface conditions: with and without galvanized surface layer. The Taguchi statistical method was used to find out the set of parameters indicated to produce joint with higher mechanical resistance. Then, the possibility of joining these dissimilar metals using the Refill FSSW process was verified. Tool rotation speed and welding time were varied to observe its effect over the joint behavior. The results of lap shear tests showed that galvanized layers do not cause any substantial change on the final joint mechanical resistance, even though different joining mechanisms had been observed.

Shear strengths and fracture behaviors of Cu/Sn37Pb/Cu soldered joints subjected to different displacement rates

The effects of displacement rate and reflow duration on the shear strengths of the Cu/Sn37Pb/Cu soldered joints as well as the interfacial microstructure were investigated after reflowing. The samples were reflowed at 300°C for different durations (5min, 15min and 30min) and then shear tested with different displacement rates ranging from 2.5×10−3 to 5×10−2mms−1. The intermetallic compounds (IMCs), including Cu6Sn5 and Cu3Sn phases were observed between Sn37Pb solder and Cu substrate, and their thicknesses increased with increasing reflow duration up to 30min. The single lap shear test results indicated that the shear forces of the joints increased with increasing displacement rate, but decreased with increasing reflow duration. Failure mechanisms of soldered joints in different displacement rate regimes were investigated based on the fractography analysis. After reflowing for 5 and 15min, the fractures of the Sn37Pb soldered joints mainly occurred inside the bulk solder irrespective of the displacement rate. While some broken Cu6Sn5 particles could be observed at the bottom of dimples in solder bulk as the high displacement rates were adopted (such as 1×10−2 and 5×10−2mms−1). In case of reflow duration of 30min, as the low displacement rates (such as 2.5×10−3 and 5×10−3mms−1) were adopted, the fracture patterns of soldered joints were similar to that of soldered joints reflowed for 5 and 15min. In contrast, little solder and many IMCs were detected on the fracture surface under high displacement rates condition (such as 1×10−2 and 5×10−2mms−1), which indicated that the fracture mainly occurred in the interior of Cu–Sn IMC layer. The displacement rate sensitivities of the soldered joints reflowed for different durations were also investigated, and it is found that the displacement rate sensitivity decreased with increasing reflow duration due to the increased interfacial IMC layer thickness.

High Performance Adhesive Bonding of High Temperature Resistant Polymer

This paper highlights effects of atmospheric pressure plasma treatment on adhesive joints of poly (ether ether ketone) (PEEK) fabricated with high temperature resistant epoxy adhesive and nano-adhesive, i.e., by dispersing carbon nanofibers (CNFs) into the adhesive matrix. Thermogravimetric analysis (TGA) demonstrates that there is an increase in thermal stability up to 15% for nano-adhesive. Substantial improvement in the surface energy of PEEK is observed after the atmospheric pressure plasma treatment. It is observed that polar component of surface energy leading to higher total surface energy of PEEK increases considerably. Atomic force microscopic (AFM) analysis of untreated and atmospheric plasma treated specimens was carried out to examine topography of the polymer surfaces. After atmospheric plasma treatment, surface roughness of the polymer increases which helps in improving the adhesion properties of the polymer. Atmospheric pressure plasma treatment results in significant increase in oxygen functionalities as detected by X-ray photoelectron spectroscopy (XPS). The improvement in adhesion properties of polymer is correlated with lap shear strength of adhesive bonded joints. Adhesive bonded joints were fabricated by employing recently developed ultrahigh temperature resistant epoxy adhesive, DURALCO 4703. Lap shear test results show that adhesion characteristic of PEEK improves considerably after atmospheric plasma treatment. Finally, the fractured surfaces of the joints were examined by scanning electron microscopy to investigate the failure mechanism.