MPa In Shear Strength Research Articles

Unveiling the strengthening effect of Nb in Ti3SiC2/Ti25Zr25Ni25Cu25 + Nb/GH3536 brazed joint

In order to achieve the ceramic/metal brazed joint with excellent mechanical properties, many kinds of high-entropy alloy (HEA) filler have been developed to acquire the joint. However, in some HEAs with high content of active element, such as Ti25Zr25Ni25Cu25 amorphous HEA, the metallurgical reaction between active element and base materials resulted in the formation of continuous intermetallics (IMCs) layer in the brazing seam inevitably, embrittling the brazed joint. In this study, Nb element was added into Ti25Zr25Ni25Cu25 amorphous HEA filler to improve the microstructure of Ti3SiC2/GH3536 brazed joint, promoting the application of Ti3SiC2 and GH3536 in the aerospace industry. After detailed characterizations, the strengthening effect of Nb in the brazed joint was unveiled. The formation of Nb-base solid solution in the brazing seam was achieved owing to the addition of Nb, which effectively inhibited the generation of large brittle IMCs bulk. Moreover, the Nb-strengthened ZrSi2 and Ni2Ti phases were generated in the reaction zone, which was also favor in promoting the mechanical properties of brazed joints. When Ti25Zr25Ni25Cu25 amorphous HEA filler with 20 vol% Nb was applied to braze Ti3SiC2 to GH3536, a maximum value of 85.36 ± 2.39 MPa for shear strength was achieved. This study illustrates the optimization mechanism of Nb in Ti25Zr25Ni25Cu25 +Nb composite filler and promotes the further application of Ti25Zr25Ni25Cu25 in brazing system.

Microstructure of Ag Nano Paste Joint and Its Influence on Reliability

In this paper, the microstructure of Ag nano paste joint was investigated in pressure-less sintering conditions, and the influence of the microstructure on the joint’s reliability was studied. Firstly, silver nanoparticles (Ag NPs) were synthesized using the redox reaction method. To tightly stack the Ag NPs in nano paste, Ag NPs with sizes of 30~50 nm and submicron-sized Ag particles were mixed. It was found that increasing the sintering temperature or sintering time can reduce the porosity of the bonding layer and the interfacial crack simultaneously, resulting in higher shear strength. When sintering at a temperature of 250 °C, a complete bonding interface was formed, with a 0.68 μm interdiffusion layer. At a higher temperature (300 °C), the bonding interface reached 1.5 μm, providing 35.9 ± 1.7 MPa of shear strength. The reliability of the die attachment was analyzed under thermal shocking from −65 °C to 150 °C for 50 cycles. As the crack could quickly grow through the interfacial defects, the separation ratio was 85% and 67% when sintered at 150 °C and 200 °C, respectively. Because of the reliable bonding interface between the die and the substrate, the Ag nano paste joint formed a slight crack on the edge of the die when sintering at 250 °C. When the joint was sintered at 300 °C, the small voids became large voids, which featured lower resistance to crack growth. Thus, instead of further improved reliability, the separation ratio increased to 37%.

In-Plane Shear Strength of Single-Lap Co-Cured Joints of Self-Reinforced Polyethylene Composites.

The present study introduces the analysis of single-lap co-cured joints of thermoplastic self-reinforced composites made with reprocessed low-density polyethylene (LDPE) and reinforced by ultra-high-molecular-weight polyethylene (UHMWPE) fibers, along with a micromechanical analysis of its constituents. A set of optimal processing conditions for manufacturing these joints by hot-press is proposed through a design of experiment using the response surface method to maximize their in-plane shear strength by carrying tensile tests on co-cured tapes. Optimal processing conditions were found at 1 bar, 115 °C, and 300 s, yielding joints with 6.88 MPa of shear strength. The shear failure is generally preceded by multiple debonding-induced longitudinal cracks both inside and outside the joint due to accumulated transversal stress. This composite demonstrated to be an interesting structural material to be more widely applied in industry, possessing extremely elevated specific mechanical properties, progressive damage of co-cured joints (thus avoiding unannounced catastrophic failures) and ultimate recyclability.

Analysis of the Impact on the Mechanical Properties of Modification of Oligohydroxyethers in Organic Solvent Solution with Rubbers.

This paper proposes and presents the chemical modification of linear hydroxyethers (LHE) with different molecular weights (380, 640, and 1830 g/mol) with the addition of three types of rubbers (polysulfide rubber (PSR), polychloroprene rubber (PCR), and styrene-butadiene rubber (SBR)). The main purpose of choosing this type of modification and the materials used was the possibility to use it in industrial settings. The modification process was conducted for a very wide range of modifier additions (rubber) per 100 g LHE. The materials obtained in the study were subjected to strength tests in order to determine the effect of the modification on functional properties. Mechanical properties of the modified materials were improved after the application of the modifier (rubber) to polyhydroxyether (up to certain modifier content). The most favorable changes in the tested materials were registered in the modification of LHE-1830 with PSR. In the case of LHE-380 and LHE-640 modified in cyclohexanol (CH) and chloroform (CF) solutions, an increase in the values of the tested properties was also obtained, but to a lesser extent than for LHE-1830. The largest changes were registered for LHE-1830 with PSR in CH solution: from 12.1 to 15.3 MPa for compressive strength tests, from 0.8 to 1.5 MPa for tensile testing, from 0.8 to 14.7 MPa for shear strength, and from 1% to 6.5% for the maximum elongation. The analysis of the available literature showed that the modification proposed by the authors has not yet been presented in any previous scientific paper.

Brazing of tungsten based alloy/superalloy GH907 with lean Cu-Ag based fillers: Wetting, interfaces and performance evaluation

Vacuum brazing of tungsten based alloy and superalloy GH907 using lean Cu-Ag based fillers (CuAg30, CuAg30V0.2, CuAg30V0.4, wt%) at 1050 °C for 20 min was investigated. CuAg30V0.4 filler showed a maximum spreading area of 132.4 mm2 and minimum contact angle of 15.94° on tungsten based alloy during wetting process. The reduction of solid–liquid surface tension and the accelerated spreading rate driven by the diffusion of V atoms synergistically promoted the wettability and brazeability. Furthermore, the formation of (Fe, Ni) diffusion layer as well as Cu-rich infiltration zone seem to be responsible for high performance of joints, which exhibited 223.83 MPa of shear strength with V content of 0.4%.

Laser-assisted conduction joining of carbon fiber reinforced sheet molding compound to dual-phase steel by a polycarbonate interlayer

This study was performed to investigate the feasibilities, characteristics and mechanisms of laser bonding heterogeneous joints from thermoset carbon fiber reinforced sheet molding compound (SMC) and dual-phase steel (DP590) with the aid of an intermediate polycarbonate (PC) mid-layer. The single lap-joint showed that the load at failure reached up to 3.31 kN (i.e. 4.9 MPa for shear strength). Morphological analysis of four fracture modes as well as mechanical characterization of the heterogeneous joints were carried out to understand the effect of laser line energy on the joint quality including defects and strength. By analyzing the relationship between the area percentage of four fracture modes and ultimate shear force (USF) of the joints with various line energies, the contribution of each fracture mode to the joint strength was determined and discussed. In addition, cross-sectional analysis indicates that bubble expansion caused by SMC substrate degradation results in carbon fibers being squeezed into molten PC, which increases the bonding area by creating wavy contacts and generates a mechanical interlock at the SMC/PC interface.

Weldability modification of conductive silver adhesion for piezoelectric composite material by co-doping of metal material and oxide material

The weldability is essential for the practical applications of conductive adhesion. In this paper we focused on the weldability through microstructure, bonding strength, and shear strength of welding spot with co-doping of metal material Al and oxide material ZnO. When Al and ZnO doped separately, it can be seen from the results that Al-doping would increase the volume resistivity and adhesion strength for welding spot, and a proper amount of ZnO-doping would decrease the volume resistivity and improve adhesion strength for welding spot. Co-doping with Al and ZnO could decrease volume resistivity and enhance adhesion strength of welding spot concurrently, and the typical properties were 1.119 × 10−4 Ω cm for volume resistivity, 34.84 MPa for shear strength, and 17.00 MPa for bonding strength with addition of 4 wt% Al and 7 wt% ZnO.

Effects of nano-TiO2 on bonding performance, structure stability and film-forming properties of starch-g-VAc based wood adhesive

The nano-TiO2 was utilized to improve the bonding performance, structure stability and film-forming properties of renewable starch-based wood adhesive. The results showed that 4% nano-TiO2 (nano-TiO2:starch, w;w) resulted in 6.5 MPa of shear strength and 6437 Pa.s of viscosity. The thermal stability was measured by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, low-field nuclear magnetic resonance (NMR) and rheological results exhibited the enhancement of nano-TiO2 on the pseudoplasticity and structure which determined the state and migration of water. Besides, the structural characterization of copolymer was analyzed via fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD). Furthermore, the film-forming property was evaluated by small angle X-ray scattering (SAXS) and dynamic mechanical analysis (DMA). The morphological structures of adhesive were observed by scanning electron microscopy (SEM). In conclusion, the 4% nano-TiO2 (nano-TiO2:starch, w;w) can be employed to prepare starch-based wood adhesives with superior properties for wood application.

Lap joining of TC4 titanium alloy to 304 stainless steel with fillet weld by GTAW using copper-based filler wire

TiFe and TiFe2 intermetallic compounds (IMCs) were effectively suppressed with copper-based filler wire when joining TC4 titanium alloy to 304 stainless steel by gas tungsten arc welding (GTAW). A Ti/Cu reaction zone, consisting of various IMCs like Ti2Cu, AlCu2Ti, TiCu, Ti3Cu4 phases, formed between TC4 substrate and the weld. Increasing welding heat input induced the formation of TiFe, TiFe2 and complex TiCuAlFe IMCs in the Ti/Cu reaction zone. The highest shear fracture load occurred at welding heat input of 2.34 kJ/cm reached 341 N/mm corresponding to 107 MPa in shear strength, and the microhardness in the Ti/Cu reaction zone was about 619 HV. Further increasing welding heat input deteriorated the shear fracture load and increased the microhardness in the Ti/Cu reaction zone. All joints fractured at the Ti/Cu reaction zone with cleavage characteristics on the fracture surface due to the brittle IMCs and micro cracks generated in the Ti/Cu reaction zone.

Preparation of Ag coating reduced graphene oxide and its application as a conductive filler to polyacrylate

By taking the advantage of the wide surface area of reduced graphene oxide (rGO), a type of carbon/metal hybrids composed by rGO coated with silver nanoparticles (Ag–rGO) has been synthesized via an easy chemical coating method. Then the Ag–rGO hybrids are filled into polyacrylate (PA) as elelctrically conductive fillers to survey the application of the hybrids in polymer based composites. Compatible research indicates the hybrids could evenly disperse in PA with a Methyl Ethyl Ketone (2-MEK) enviroment for a long period. Property measurements suggest that the Ag–rGO dual fillers have greatly improved the electrical conductivity of PA matrix, enabling the conductive of the Ag–rGO/PA composites to rise more than ten orders while reducing the main bonding performance of the composites. With 10.0 wt% of Ag–rGO hybrids, the composites exhibited optimized electrically conducting and mechanical properties, which were 2.40 × 10−2 S/cm of conductivity, 0.62 KN/m of 180°peel strength and 0.67 MPa of shear strength. The great effect on PA is caused by the electrical conducting of nano-scaled Ag particles and the intermolecular forces between rGO and PA.

Wafer-Level Vacuum Packaging Enabled by Plastic Deformation and Low-Temperature Welding of Copper Sealing Rings With a Small Footprint

Wafer-level vacuum packaging is vital in the fabrication of many microelectromechanical systems (MEMS) devices and enables significant cost reduction in high-volume MEMS production. In this paper, we propose a low-temperature wafer-level vacuum packaging method based on plastic deformation and low-temperature welding of copper sealing rings with a small footprint. A device wafer with copper ring structures and a cap wafer with corresponding metalized grooves are placed inside a vacuum chamber and pressed together at a temperature of 250 °C, resulting in low-temperature welding of the copper, and thus, hermetic sealing of the cavities enclosed by the sealing rings. The vacuum pressure inside the fabricated cavities 146 days after bonding was measured using residual gas analysis to be as low as $2.6\times 10^{-2}$ mbar. Based on this value, the leak rate is calculated to be smaller than $ {3.6}\times {10}^{-16}$ mbarL/s using the most conservative assumptions, demonstrating the excellent hermeticity of the seals. Shear testing was used to demonstrate that the seals are mechanically stable with over 90 MPa in shear strength for $5.2~\mu \text{m}$ -high Cu sealing rings with widths down to $8~\mu \text{m}$ . The reported method is potentially compatible with complementary metal-oxide-semiconductor (CMOS) substrates and may be applied to vacuum packaging of 3-D heterogeneously integrated MEMS on state-of-the-art CMOS substrates. [2016-0252]

Highly Adhesive Phenolic Compounds as Interfacial Primers for Bone Fracture Fixations

Bone fractures are today stabilized with screws and metal plates. More complicated fractures require alternative treatments that exclude harsh surgical conditions. By adapting the benign and UV initiated thiol-ene reaction, we efficiently fabricated triazine-based, fiber-reinforced adhesive patches within 2 s. To enhance their bone adhesion properties, we found that a pre-treatment step of bone surfaces with phenolic dopamine and poly(parahydroxystyrene) compounds was successful. The latter display the greatest E-module of 3.4 MPa in shear strength. All patches exhibited low cytotoxicity and can therefore find potential use in future treatments of bone fractures.