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Open access

Stanisław Karczmarzyk

Abstract

The aim of this paper is to compare some geometric parameters and deflections of a sandwich meta-structure with its classic, three-layer counterpart. Both structures are composed of the same materials and have the same external dimensions and mass, but their middle layers (cores) are different. The core of the sandwich meta-structure is a new spatial structure itself, consisting of there-layer bars. The core of the classic sandwich structure is a layer of the continuum. To make the comparison more general and convincing, three geometrical parameters, i.e., ratio of interfacial contact (Ric), interlayer bonding factor (Ibf) and coefficient of impact sensitivity (Cis), were introduced and applied. Deflections of the structures, simply supported at the edges and loaded in the mid-span by a static force, have been measured and are presented in the paper. Potential advantages of the new meta-structure are briefly outlined.

Open access

S.H. Park, D.B. Kim, R.G. Lee and I.J. Son

Abstract

This study focuses on the fabrication of thermal management material for power electronics applications using graphite flake reinforced copper composites. The manufacturing route involved electroless plating of copper in the graphite flake and sintering process are optimized. The microstructures, interface, thermal properties, and relative density of graphite/Cu composites are investigated. The relative density of the composites shows 99.5% after sintering. Thermal conductivities and coefficients of thermal expansion of this composites were 400-480 Wm−1K−1 and 8 to 5 ppm k−1, respectively. Obtained graphite nanoplatelets-reinforced composites exhibit excellent thermo-physical properties to meet the heat dispersion and matching requirements of power electronic devices to the packaging materials.

Open access

D. Szczech and R. Kotynia

, Volume 39, Issue 5, July 2008, Pages 747-755. 7. Kotynia, R., Szczech, D., Kaszubska, M. “Bond behaviour of GRFP bars to concrete in beam test”. Procedia Engineering 2017, (193), 401–408. 8. Lee JY, Kim TY, Kim TJ, Yi CK, Park JS, et al. „Interfacial bond strength of glass fibre reinforced polymer bars in high-strength concrete”. Composites: Part B 2008;39(2):258–70. 9. Pecce M, Manfredi G, Realfonzo R, Cosenza E. “Experimental and analytical evaluation of bond properties of GFRP bars”. Journal of Materials in Civil Engineering 2001

Open access

Qijie Xu, Fangfei Chen, Xiaohong Li and Zhijun Zhang

Abstract

The present study investigated the effect of the surface functional groups of nanosilica on the interfacial, crystallization, and thermal stability of polyamide 6/SiO2 (PA6/SiO2) nanocomposite, in which nanosilica was modified in situ with both 3-triethoxysilylpropylamine and 3-methacryloxypropyltrimethoxy silane¬ (KH-550 and KH-570). The FTIR analysis results showed the chemical bonding action between the reacting amino groups of nanosilica and end carboxyl groups of polyamide 6 enhanced with increasing the ratio of KH-550 and KH-570. The XRD spectrum indicated that the crystal structure of PA6/SiO2 nanocomposites tended to form α crystal type that was beneficial to an improvement of mechanical properties, and which was in agreement with the results of mechanical strength measurements. It was also found that crystallization temperature and crystallization rate of PA6/SiO2 nanocomposites were lower than that of neat polyamide 6.

Open access

Ivana Schwarzová

Abstract

The effort to achieve sustainable development using renewable materials instead of limited ones is the current trend in the construction industry. Need for the development of environmentally friendly products is related to industrial interest in using natural plant fibres as reinforcement in composites. The combination of organic filler and inorganic matrix creates high-quality products such as fibre boards and composites. Industrial hemp fibres are one of the mostly used natural fibres and due to their unique mechanical, thermal insulation, acoustic and antiseptic properties have a great potential in composite materials. However, improving the interfacial bond between fibre and matrix is an important factor in fibre-reinforced composites. Optimizing the adhesion between fibre and inorganic matrix is related to surface treatment processes. This paper deals with morphology characterization, study changes in the chemical composition and structure of hemp fibres using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) before and after physico-chemical treatment.

Open access

H. Ates and N. Kaya

Abstract

Rotary Friction welding is one of the most popular methods of joining similar and dissimilar materials. It is widely used with metals and thermoplastics in a wide variety of aviation, transport and aerospace industrial component designs. This study investigates the influence of friction and upsetting pressures on the hardness, tensile properties and microstructure of the welds. The experimental results showed that as the friction and upsetting pressures increased, the hardness and tensile strength values increased, as well. The tensile fracture of welded joint occurred in the AISI 1060 side. The friction processed joints were evaluated for their integrity and quality aspects by optical and scanning electron microscopy. For the perfect interfacial bonding, sufficient upsetting and friction pressures are necessary to reach the optimal temperature and severe plastic deformation to bring these materials within the attraction range.

Open access

G. Szabó

REFERENCES [1] N. Bay, Cold welding Part I Characteristic bonding mechanisms bond strength, Met. Const. 369 (1986). [2] M. Eizadjou, H. Danesh Manesh, K. Janghorban, Mechanism of warm and cold roll bonding of aluminum alloy strips, Mat. and Des. 4156 (2009). [3] W. Zhang, N. Bay, Cold welding-theoretical modeling of weld formation, J. Weld. 417 (1997). [4] P.K. Wright, D.A. Snow, C.K. Tay, Interfacial conditions and bond strength in cold pressure welding by rolling, Met. Technol. 24 (1978). [5] H.Y. Wu, S. Lee, J.Y. Wang

Open access

J.J. Oak, Y.C. Lee and Y.H. Park

Abstract

In this study, the newly designed Al-9Si/SiC particles (SiCp) + Ti-fiber (2step-reinforced Al-9Si alloy matrix) metal matrix composites (MMCs) were fabricated by hot-pressing sintering at 560°C. 2step-reinforced Al-based MMCs were characterized by thermal shrinkage, phase transition, microstructure and tensile strength. The addition of Ti-fiber reduced thermal shrinkage was caused by temperature difference in sintering process as well as enhanced assistance for tensile strength and plastic deformation at room temperature. Experimental results reveal that the 2step-reinforcment sintering by ceramic and metal has a significant effect to increase interface bonding in boundary of each component material and the improved mechanical properties were due to the influence of interfacial product by diffusion. Tensile strength and elongation at room temperature by 2step-reinforcement were improved in 19.5% and 26.2% more than those of Al-9Si/SiCp, respectively. Especially, it reveals that diffusion direction may be varied by sintering methods at low temperature in this study.

Open access

M. Behera and G. Giri

Abstract

Herein, we report a facile green synthesis of Cu2O nanoparticles (NPs) using copper sulfate as precursor salt and hydrazine hydrate as reducing agent in presence of bio-surfactant (i.e. leaves extract of arka — a perennial shrub) at 60 to 70 °C in an aqueous medium. A broad band centered at 460 nm in absorption spectrum reveals the formation of surfactant stabilized Cu2O NPs. X-ray diffraction pattern of the surfactant stabilized NPs suggests the formation of only Cu2O phase in assistance of a bio-surfactant with the crystallite size of ∼8 nm. A negative zeta potential of −12 mV at 8.0 pH in surfactant stabilized Cu2O NPs hints non-bonding electron transfer from O-atom of saponin to the surface of NP. Red-shift in the vibrational band (Cu-O stretching) of Cu2O from 637 cm−1 to 640 cm−1 in presence of bio-surfactant suggests an interfacial interaction between NPs and O-atoms of -OH groups of saponin present in the plant (i.e. Calotropis gigantean) extract. From X-ray photoelectron spectroscopy spectra, a decrease in binding energy of both 2p3/2 and 2p1/2 bands in Cu2O with saponin molecules as compared to bulk Cu atom reveals a charge transfer interaction between NP and saponin surfactant molecules. Transmission electron microscopy images show crystalline nature of Cu2O NPs with an fcc lattice.

Open access

H. Soflaei and S.E. Vahdat

References [1] A.S.M. Handbook, Vol. 6, (1993). Welding, Brazing, and Soldering , 9 ed., ASM International, Ohio, USA. [2] Liu, Z.H., Zhang, D.Q., Sing, S.L., Chua, C.K. & Loh, L.E. (2014). Interfacial characterization of SLM parts in multimaterial processing: Metallurgical diffusion between 316L stainless steel and C18400 copper alloy, Materials Characterizatio. 94. 116-125. [3] Atabaki, M.M. Wati, J.N., Idris, J.B. (2011). Transient liquid phase diffusion bonding of stainless steel 304 using copper and aluminium filler interlayers, ASM Heat