• Journal of Welding and Joining
• /
• v.17 no.2
• /
• pp.104-111
• /
• 1999

The interfacial microstructure and bond strength were examined for WC-Co/Cu/SM45C steel join using a nickel-plated copper in vacuum at 1323K for 0.6ks∼3.6ks. After bonding, microstructure in bonding interface was observed by OM(Optical Microscopy), SEM(Scanning Electron Microscopy) and EPMA(Eelectron Probe Micro Analyzer). The oil cooling was carried out at 353K, the cooling rate in air and furnace was 22K/s and 4.4K/s. respectively. It was found that dendritic widths increased with the content of cobalt and bonding times at 1323K. As a whole, bond strength values at the same bonding condition decreased in this order: WC-13wt.%Co/SM45Csteel. WC-8wt.%Co/SM45Csteel and WC-4wt.%Co/SM45Csteel. The bond strength of WC-13wt.%Co/S45C steel joint in oil cooling was 273MPa. This value was greatly higher than those of 125MPa in furnace cooling and 93MPa in air cooling at 1323K for 0.6ks. The bond strength values were found to be closely associated with the content of cobalt in WC-Co and cooling rate.

• Korean Journal of Materials Research
• /
• v.20 no.9
• /
• pp.478-482
• /
• 2010

A series of molecular dynamic (MD), finite element (FE) and ab initio simulations are carried out to establish suitable modeling schemes for the continuum-based analysis of aluminum matrix nanocomposites reinforced with carbon nanotubes (CNTs). From a comparison of the MD with FE models and inferences based on bond structures and electron distributions, we propose that the effective thickness of a CNT wall for its continuum representation should be related to the graphitic inter-planar spacing of 3.4${\AA}$. We also show that shell element representation of a CNT structure in the FE models properly simulated the carbon-carbon covalent bonding and long-range interactions in terms of the load-displacement behaviors. Estimation of the effective interfacial elastic properties by ab initio simulations showed that the in-plane interfacial bond strength is negligibly weaker than the normal counterpart due to the nature of the weak secondary bonding at the CNT-Al interface. Therefore, we suggest that a third-phase solid element representation of the CNT-Al interface in nanocomposites is not physically meaningful and that spring or bar element representation of the weak interfacial bonding would be more appropriate as in the cases of polymer matrix counterparts. The possibility of treating the interface as a simply contacted phase boundary is also discussed.

• Restorative Dentistry and Endodontics
• /
• v.20 no.1
• /
• pp.289-302
• /
• 1995

The purpose of this study was to estimate the shear bond strength and observe the fractured and interfacial surfaces of various dentin bonding agents used conjunction with a visible light cured composite. The senentytwo human premolars and molars extracted due to periodontal or orthodontic reasons were used and randomely divided into six groups. All the prepared dentin surfaces were treated with Superbond D-liner, Scotchbond Multi-Purpose, All-Bond 2 and Prisma Universal Bond 3 accroding to the manufacturer's instructions. Six specimens were then demineralized in 10 % HCl for 24 hours and the other six specimens were not demineralized in order to observe the interfacial surfaces with Hitachi X-450 SEM at 25Kv. Also shear bond strength were obtained using an Instron Testing Machine with a crosshead speed of 1mm/min. The following results were obtained : 1. Although shear bond strength of Superbond D-Liner(17.35 MPa) and Scotch-bond Multi-Purpose group(17.29 MPa) were higher than the All-Bond 2(12.80 MPa) and Prisma Universial Bond 3 (13.43 MPa), there were no significant statistic differences in the shear bond strength between 4 groups.(P<0.05) As a result of etching to dentin in Prism a Universial BOND 3 experimentally, the resin tag was formed, but shear bond strength was decreased. 2. The resin tag into the opened dentinal tubule was formed in Superbond D-Liner, Scotchbond Multi-Purpose, All-Bond 2(etching) and Prisma Universial Bond 3(etching), but not in the All-Bone 2 and Prism a Universial Bond 3(non-etching). 3. Strong, durable bonds between dentin and dentinal bonding agents are essential, not only resin tag into the dentinal tubules, but also hybrid layer.

• Korean Journal of Metals and Materials
• /
• v.47 no.1
• /
• pp.26-31
• /
• 2009

The effects of $Ar/O_2$ ion-beam pre-treatment conditions on the interfacial adhesion energy of sputterdeposited Cu thin film to FR-4 substrate were systematically investigated in order to understand the interfacial bonding mechanism for practical application to advanced chip-in-substrate package systems. Measured peel strength increases from $45.8{\pm}5.7g/mm$ to $61.3{\pm}2.4g/mm$ by $Ar/O_2$ ion-beam pre-treatment with anode voltage of 64 V. Interfacial bonding mechanism between sputter-deposited Cu film and FR-4 substrate seems to be dominated by chemical bonding effect rather than mechanical interlocking effect. It is found that chemical bonding intensity between carbon and oxygen at FR-4 surface increases due to $Ar/O_2$ ion-beam pretreatment, which seems to be related to the strong adhesion energy between sputter-deposited Cu film and FR-4 substrate.

• The Journal of Korean Academy of Prosthodontics
• /
• v.30 no.2
• /
• pp.135-154
• /
• 1992

This study was performed to analyze bond strength, the alterations of the interfaces between metal films which are populary used and considered to contribute to the chemical reaction with porcelain, according to constant ion- beam- mixing, and the relation between interfacial chemical reactions and bond strength in metal/porcelain specimens. For this study, three seperate metals : selected-gold, indium and tin were chosen ; each to be bonded to a seperate body porcelain. Bonding occurs when the metal is deposited to the body porcelain using a vacuum evaporator. The vacuum evaporator used $10^{-5}\sim10^{-6}$ Torr vacuum states for the evaporation of various metals (Au, Sn, In). Ion-beam-mixing of the porcelain/metal interfaces caused reactions when the Ar+ was implanted into thin films using a 80 KeV accelerator. These ion-beam-mixed specimens were then compared with an unmixed control group. An analysis of bond strength and ionic changes between the the metal and porcelain was performed by electron spectroscopy of chemical analysis (ESCA) and scratch test. The finding led to the following conclusions : 1. Light microscopic views of the scratch test : The ion-beam-mixed Au/porcelain specimen showed narrower scratched streams than the unmixed specimen. However, the Sn/porcelain, In/porcelain specimens showed no differences in the two conditions. 2. Acoustic emissions in scratch tests : The ion-mixed Au/porcelain, In/porcelain specimens showed signals closer to the metal/porcelain interfaces than unmixed specimens. Conversely, the ion-mixed Sn/porcelain specimen showed more critical signals in superficial portions than unmixed specimens. 3. After ion- beam-mixing, the Au/porcelain specimen showed apparently increased bond strength, and the In/porcelain specimen showed very slightly increased bond strength. However, the Sn/porcelain specimen showed no differences between ion mixed specimen and the unmixed one. 4. ESCA analysis : The ion-beam-mixed Au/porcelain specimen showed a higher peak separated value (4.3eV) than that of the unmixed specimen(3.65eV), the ion-beam-mixed In/porcelain specimen showed a higher peak separated value (9.43eV) than that of the unmixed specimen(7.6eV) and the ion-beam-mixed Sn/porcelain specimen showed a higher peak separated value (8.79eV) than that of the unmixed specimen(8.5eV). 5. Interfacial changes were observed in the ion-mixed Au/porcelain, In/porcelain and Sn/porcelain specimens. Especially, significant interfacial changes were measured in the ion- mixed Sn/porcelain specimen. Tin dioxide(SnO2) and a combination of pure tin and tin dioxide (Sn+SnO2) were produced. 6. In the Au/porcelain specimen, the interfacial chemical reaction showed increased bond strength between gold and porcelain substrate. But, in the In/porcelain, Sn/porcelain specimens, interfacial chemical reactions did not affected the bond strength between metal and porcelain substrate. Especially, bonding strength on the ion mixed Sn/porcelain specimen showed the least amount of difference.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2005.04a
• /
• pp.111-115
• /
• 2005

Recently, natural fibers draw much interests in composite industry due to low cost, light weight, and environment-friendly characteristics compared with glass fibers. In this study, mechanical properties were evaluated for two extreme cases of jute fiber orientations, i.e. the unidirectional yarn composites and the felt fabric composites. Samples of jute fiber composites were fabricated by RTM process using epoxy resin, and tensile, compression, and shear tests were conducted. As can be expected, unidirectional fiber specimens in longitudinal direction showed the highest strength and modulus. Compared with glass/epoxy composites of the similar fabric architecture and fiber volume fraction, the tensile strength and modulus of jute felt/epoxy composites reached only 40% and 50% levels. However, the specific tensile strength and modulus increased to 80% and 90% of the glass/epoxy composites. The main reason for the poor mechanical properties of jute composites is associated with the weak interfacial bonding between fiber and matrix. The effect of surface treatment of jute fibers on the interfacial bonding will be examined in the future work.

• Composites Research
• /
• v.27 no.5
• /
• pp.196-200
• /
• 2014

A novel, simple and totally recyclable method has been developed for the synthesis of nontoxic, biocompatible and biodegradable bio-composite films from soy protein and silk protein. Bio films are defined as flexible films prepared from biological materials such as protein. These materials have potential application in medical and food as a packaging material. Their use depends on various parameters such as mechanical (strength and modulus), thermal, among others. In this study, prepare and characterization of bio films made from Soy Protein Isolate (SPI) (matrix) and Silk Fiber (SF) (reinforcement) through solution casting method by the addition of plasticizer and crosslinking agent. The obtained SPI and SPI/SF composites were subsequently subjected to evaluate their mechanical and thermal properties by using Universal Testing Machine and Thermal Gravimetric Analyzer respectively. The tensile testing showed significant improvements in strength with increasing amount of SF content and the % elongation at break of the composites of the SPI/SF was lower than that of the matrix. Though the interfacial bonding was moderate, the improvement in tensile strength and modulus was attributed to the higher tensile properties of the silk fiber.

• Journal of Welding and Joining
• /
• v.29 no.6
• /
• pp.49-55
• /
• 2011

With the development of pre-painted steel sheets for automotive body application, a new joining method is required such as hybrid joining with combination of adhesive bonding and mechanical joining. The objective of this study is to investigate the effect of pre- and post-baking of adhesive bonding on failure mode and strength of hybrid joining of automotive steel sheets. Experiments show that the hybrid joining exhibits better bonding strength and displacement than conventional adhesive joining and mechanical fastening each. Comparison of pre- and post-baked hybrid joining results suggested that baking at $160^{\circ}C$ after mechanical joining was found to have higher joining properties than pre-baking condition. The prebaking condition changed its fracture mode from interfacial to button fracture. The changes in fracture mode with post-baking of hybrid joining was attributed to variation in neck thickness and undercut of joint.

• International Journal of Korean Welding Society
• /
• v.4 no.1
• /
• pp.53-60
• /
• 2004

Adhesive-bonded joints are widely used in the industry. Recently, applications of adhesive bonding joints have been increased extensively in automobile and aircraft industry. The strength of adhesive joints is influenced by the surface roughness, adhesive shape, stress distribution, and etc. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, as the fundamental research of adhesive bonding joints, the effects of adhesive shape and loading speed on bonding strength properties and durability of aluminum to polycarbonate single-lap joints were studied. To evaluate the effect of adhesive shape, several modified shapes were used, and loading speeds were varied from 0.05 to 5mm/min. As a result, the load distribution showed a brittle fracture tendency. The trigonal edged single lap and bevelled lap joints showed the higher strength than the plain single lap, trigonal single lap, joggle lap and double lap joints in same adhesive area. The fractures of trigonal single lap and trigonal edged single lap joints that had the higher strength level were shown as the mixture type of the cohesive and interfacial-failure, mostly joggle lap joints that had the lower strength level were shown as the adhesive-failure.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.6
• /
• pp.783-790
• /
• 2004

Adhesive-bonded joints are widely used in the industry. Recently, applications of adhesive bonding joints have been increased extensively in automobile and aircraft industry. The strength of adhesive joints is influenced by the surface roughness, adhesive shape, stress distribution, and etc. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, as the fundamental research of adhesive bonding joints, the effects of adhesive shape and loading speed on bonding strength properties and durability of aluminum to polycarbonate single-lap joints were studied. To evaluate the effect of adhesive shape, several modified shapes were used, and loading speeds were varied from 0.05 to 5 mm/min. As a result, the load-displacement distribution was shown a brittle fracture tendency. The trigonal edged single lap and bevelled lap joints showed the higher strength than the plain single lap, trigonal single lap, joggle lap and double lap joints in same adhesive area. The fractures of trigonal single lap and trigonal edged single lap joints that had the higher strength level were shown as the mixture type of the cohesive and interfacial-failure, mostly joggle lap joints that had the lower strength level were shown as the adhesive-failure.