Keywords : mechanical properties

Influence of Processing Induced Morphology on the Performance of PP Injected Intricate Pieces Modified with MWCNT as a Painting Aide

Alejandra Costantino; Leandro Ramajo; Julio Viana; Caren Rosales; Antonio Pontes; Valeria Pettarin

Advanced Materials Letters, 2021, Volume 12, Issue 4, Pages 1-10
DOI: 10.5185/amlett.2021.041618

Carbon nanotubes are currently added to polymers to avoid extra-stages in the electrostatic painting process. However, the attained particle network after processing a final part could affect the mechanical properties and thermal stability of nanocomposites. It is then important to evaluate not only the functional properties, but also the overall performance of these pieces. In this work, boxes of polypropylene (PP) modified with multi-walled carbon nanotubes (MWCNT) were injection molded. Morphology induced by processing was characterized at different locations of the moldings to correlate the influence of in-homogeneities and flow pattern with the overall performance of the molded boxes. PP/MWCNT presented a better aesthetic quality and a markedly better thermal stability than pure PP. It was confirmed that the nanocomposite has high dielectric permittivity, low dielectric losses and relatively good DC conductivity. Regarding mechanical properties, MWCNT induced a slight improvement in flexural elastic modulus. Although fracture initiated at practically the same loading levels for both materials, the propagation energy was deteriorated by MWCNT presence. Differences in both electrical and mechanical behavior were found trough out the PP/MWCNT pieces as result of distinct MWCNT orientation and distribution. It was then concluded that processing has a great influence on parts performance.

Flaw Resistance and Mode - I Fracture Energy Redistribution in Bamboo - A Correlation

Sayyad Mannan

Advanced Materials Letters, 2021, Volume 12, Issue 3, Pages 1-6
DOI: 10.5185/amlett.2021.031615

Bamboo is a unidirectional fibre-reinforced composite with radially graded and almost transversely isotropic elastic properties. The cracks originated in bamboo under bending due to wind loads propagate along the fibre direction. This process is controlled by interlaminar fracture toughness. In order to observe the spatial distribution of the fracture toughness in bamboo, energy release rate is theoretically deduced from the general equations for crack-tip stress fields in anisotropic bodies. The analysis shows that the fracture toughness has graded distribution and the trend is opposite to that of axial modulus. To verify this, the energy release rate (or fracture toughness) is experimentally calculated for double cantilever beam specimens (with a crack placed in different fibre density region) in mode-I i.e. crack opening mode. It is observed that the crack propagation parallel to fibres (splitting) develops easily and the energy release rate decreases with increased density of fibre bundles. The observed trend closely corroborates the results from theoretical analysis. From the results of real-time wind load simulations (reported elsewhere) on tapered bamboo-like structure it is concluded that with the help of radially graded fracture toughness bamboo converts flaws of all orientations into splitting mode.

Synergistic Utilization of Flax Fiber Polymer Composites: A Review

K. Arunprasath; V. Arumugaprabu; P. Amuthakkannan; V. Manikandan

Advanced Materials Letters, 2021, Volume 12, Issue 1, Pages 1-9
DOI: 10.5185/amlett.2021.011590

The application of flax fiber is vast in the various fields in the world, the well-known in the area of as textiles many of the countries they used the flax fiber mixture with linen, traditionally used for making of bed sheets, underclothes and table linen. The specific properties of flax fiber responsible for the potential platform to next-generation structural applications in automobile and other consumer works. Due to its mechanical properties, flax fiber composites possess good strength and durability. In this review paper, the various proportion on evaluation of work done to know about the amount of research undergone with flax fiber composite in various fields. From this review paper, the utilization of flax fiber has gap in variety of applications in various fields. To identify the research gap and its utilization, quantum of work to be done in the all of the areas was analyzed in that 36% of work done on mechanical property, 30% in novel performance work like simulation and model analysis, 18% of work going on marine, aeronautical related applications and only 16% work carried out in structural related applications using flax fiber composite, flax fiber composite products are potentially used because of their lighter weight and lower cost. Most of the automobile components are replaced by flax fiber composite, these composite components are sound in the capability to reduce the weight for fuel efficiency. Other developing market applications such as tiles, marine piers and flower pots are now a day manufactured from flax fiber composite. In the future, the flax fiber will reduce the utilization of synthetic fiber, by producing an eco-friendly environment in all type of products, wherever replacement is possible with some synergic property.

Elaboration and Characterization of Macroporous Bioceramics using Polymeric Sponge Replication Method

Kamel Chaari; Jamel Bouaziz; Khaled Bouzouita

Advanced Materials Letters, 2020, Volume 11, Issue 11, Pages 1-6
DOI: 10.5185/amlett.2020.111578

Biomedical porous fluorapatite scaffolds were fabricated using an improved polymeric sponge replication method. The specific formulations and distinct processing techniques such as the mixture of water and dispersant (Sodium TriPolyPhosphate) as solvent, the multiple coatings with the desired viscosity of the Fap slurries were duplicated from Chaari et al. [11]. The heat treatment was conducted in two stages: a delicate stage of polymeric structure degradation at 290 0 C and then at 600 0 C followed by a sintering stage at 1000 0 C for three hours. The obtained porous Fap scaffolds had uniform porous structures with completely interconnected macropores of 850 μm. In addition, micropores of 4 μm were formed in the skeleton of the scaffold. Finally, the porous Fap scaffold with a porosity of 65 vol.% and a surface of 400 mm 2 had a compressive strength of 7 MPa.

Are the Electrospun Polymers Polymeric Fibers?

S. Fakirov

Advanced Materials Letters, 2020, Volume 11, Issue 1, Pages 1-3
DOI: 10.5185/amlett.2020.011456

In this short communication, an attempt is undertaken to demonstrate that the widely used practice to call the electrospun polymers from their solutions and melts “polymer nanofibers” is hardly correct for the following reasons. The polymer fibers prepared by means of the common melt-spinning are characterized by perfect molecular orientation of the parallel aligned macromolecules leading to superior mechanical performance. The electrospun polymers are also flexible cylindrical formations but with macromolecules in isotropic, non-oriented state and distinguished by poor mechanical properties, frequently inferior than those of the same polymer in isotropic state. For this reason, it is suggested to call these materials “fiber-like nanomaterials” instead of “polymer nanofiber”. The real target of the communication is to challenge the electrospinning community to modify the manufacturing process in such a way that the final nanomaterial is characterized by perfect molecular orientation resulting in excellent, typical for polymer fibers mechanical properties, which will offer wide real applications of these nanofibers. 

Anisotropic and Nonlinear Mechanical Properties in Two-dimensional Nanomaterials

Ming Yu; Congyan Zhang; Safia Abdullah R Alharbi; Anna Zeng; Kevin Zeng; Emily Liu

Advanced Materials Letters, 2019, Volume 10, Issue 12, Pages 880-886
DOI: 10.5185/amlett.2019.0051

A systematic computational calculation based on the state-of-the-art quantum mechanics mothed was carried out to study the response of mechanical properties to various strains exerted on graphene, SiC sheet, and recently predicted two-dimensional (2D) sandwiched GaP and InP binary compounds. It was found that these 2D materials undergo an elastic expansion, a structural deformation, and then a structural broken process as the strain increases. Such process strongly depends on the direction of the strain exerted on 2D materials. In particular, a phase transition occurs in 2D sandwiched GaP and InP binary compounds when the strain exerts in zigzag direction. Calculated mechanical properties show that graphene has large linear and nonlinear elastic moduli, followed by 2D SiC monolayer. While the sandwiched GaP and InP structures possess significant anisotropic and nonlinear mechanical properties. Especially, those constants in the zigzag direction are about three to nine times greater than that in the armchair direction. Compared to graphene, they are softer, even along the zigzag direction. Such results provide fundamental information at atomic level for synthesizing, designing, and fabricating nanoelectromechanical and nanoelectronic devices. Copyright © VBRI Press.

Investigating the Machinability of Metallic Matrix Composites Reinforced by Carbon Nanotubes: A Review

Robiul Islam Rubel; Md. Hasan Ali; Md. Abu Jafor; Sk. Suzauddin Yusuf

Advanced Materials Letters, 2019, Volume 10, Issue 11, Pages 786-792
DOI: 10.5185/amlett.2019.0025

The modern manufacturing technology tends to innovate different materials with simultaneous low density in weight, porosity, high toughness, corrosion resistance, thermal and electrical properties etc. Metallic matrix-based carbon nanotubes composites (CNTs) are a relatively new material concept. The CNT reinforced composite materials harvest the dual benefit of alloying metals with high mechanical properties of CNTs. Besides, the materials being innovated must have good forming or machining characteristics. However, no machining data or machining model are yet available for these newly developed composites. In this work, the mechanical machining of metal-matrix/CNTs composites has studied to review the available data and better understanding the material removal behaviour. The work also concludes on the suggestive machining techniques adopted that will not affect the structural deformation, mechanical, thermal, electrical properties as well as must not alter the mechanical characteristics of the machined surface. The present study will assist in optimizing the manufacturing composites with desirable mechanical properties in future CNT reinforced composite developments. Copyright © VBRI Press.

Study of microstructure and mechanical properties of friction stir welded ferrite-martensite DP700 steel

Mahdi Mahmoudiniya; Leo A.I. Kestens; Shahram Kheirandish; Amir Hossein Kokabi

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 515-518
DOI: 10.5185/amlett.2019.2211

In the present study, a 2 mm thick ferrite-martensite dual phase steel was subjected to friction stir welding. The welding was conducted by a tungsten carbide tool at a constant rotational speed of 800 rpm and various feed rates of 50, 100 and 150 mm/min. The microstructural features of friction stir welded joints were characterized by field emission - scanning electron microscopy as well as by transmission electron microscopy. The relationship between microstructure and tensile properties of the joints was investigated. Results showed that the stir zone of the welds consisted of bainite packets, exhibiting a different morphology compared to the ferrite phase and to the martensite phase. Microstructural examination of the heat affected zone showed that there is a softened region in the heat affected zone in all joints, irrespective of the welding speed. Decomposition of the martensite phase during tempering of the initial martensite of the base material was responsible for the observed hardness reduction. The decrease of the hardness in the softened zone was 28 ± 3, 21 ± 2.5 and 15 ± 3.2 HV for welding speeds of 50, 100 and 150 mm/min, respectively; whereby the base material exhibited a hardness of 275 ± 3 HV. The lower softening corresponded to the higher welding speed, i.e., under conditions whereby heat input to the weld was minimum. The tensile test results showed that the ultimate tensile strength of all welded joints is lower than the base metal and failure takes place in the softened region of the joints. The increment of welding speed increased the strength of the joint so that the weld conducted at the highest welding speed (150 mm/min) showed the highest tensile strength of 687 MPa, i.e. 95% of the strength of the base metal (723 MPa). Copyright © VBRI Press.

Analysis of machined electron beam treated Ti6Al4V-ELI implant surfaces

Miroslav Piska; Katrin Buckova

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 381-385
DOI: 10.5185/amlett.2019.2229

This work contributes to the problem of individual replacements of human joints by applying new types of implants and materials, made using modern additive technologies (melting of metal powders by laser and electron beam). The main attention is paid to the method called Electron Beam Melting used with the ARCAM Q10plus machine. Analyses of the sintered Ti6Al4V - ELI alloy samples were made from the point of view of production precision and quality after sintering in different technological modes and the surface quality reached after turning and tumbling, including measurement of other physical quantities. The results confirm an important effect of sample inclination in the chamber when building on the precision of the shape and quality of the surface. The tensile strengths were high (up to 1,012 MPa) and statistically consistent. Furthermore, the material exhibited high resistance to machining, expressed in terms of force loading and specific cutting forces, measured for a range of feed per rotation 0.05-0.40mm, cutting speed 48 m/min, depth of cut 1.0 mm and use of coated cemented carbides, in dry cutting conditions. Nevertheless, high quality after machining can be reached. The quality can be improved more by two-steps tumbling technology so finally, a glossy surfaces (Ra< 0.036 um) with high material ratios (Abbot-Firestone curves) and convenient tribological properties were found. Ongoing research is focused on studies of milling and belt grinding technology and fatigue properties in tensile R 0.1 mode of loading.

Physical and mechanical properties of microwave absorber material containing micro and nano barium ferrite  

Hashem Al-Mattarneh; Mohamed Dahim

Advanced Materials Letters, 2019, Volume 10, Issue 4, Pages 259-262
DOI: 10.5185/amlett.2019.2226

The rapid development of electronic systems and telecommunications has resulted in a growing and intense interest in microwave electromagnetic absorber technology and microwave absorber materials. In this study, thermoplastic natural rubber barium ferrite composite was developed using micro and Nano barium ferrite filler. This paper presented the improvement of the mechanical properties of the thermoplastic natural rubber barium ferrite (TPNR-BF) composite when the size of barium ferrite filler changed from 3 um to 55 nm. TPNR was prepared as hosting material, and the barium ferrite with particle size 3 um was used as filler. Five samples of the composite were prepared with barium ferrite content range from 0% to 20% by an increment of 5%. The same procedure was used to prepare five samples using barium ferrite with a particle size of 55 nm. Physical and Mechanical properties of the composite were determined such as density, SEM, hardness, stiffness, tensile stress, and strain. Also, the magnetic properties and hysteresis diagram and SEM were evaluated for both composites barium ferrite types. The results indicate that all mechanical properties decline with the increasing BF content due to the increasing size of the weak interfacial zone between the polymer and the filler. This trend could be enhanced by replacing the micro barium ferrite with Nanosize barium ferrite. The level of improvement in mechanical properties increases at high filler content.

Development of anti-bio deteriorate sustainable geopolymer by SiO2 NPs decorated ZnO NRs 

Manas Sarkar; Moumita Maiti; Muhammad Akbar Malik; Shilang Xu

Advanced Materials Letters, 2019, Volume 10, Issue 2, Pages 128-131
DOI: 10.5185/amlett.2019.2166

In concrete industry, geopolymer acts as an alternative building material of ordinary cement and possess similar/greater mechanical strength and durability, fashioned by industrial by-product; fly ash with alkaline activator. Accompanied by the chemical corrosion, biogenic corrosion is a foremost obstruction in sewer systems, bridge piers, pipelines and offshore platforms. The present works has been given an effort to introduce an anti-bio deteriorate sustainable geopolymer (GMZnO–Si) through the decoration of spherical nano silica (Si) on zinc oxide Nano-rods (ZnO NRs) surface. XRD, Zeta potential, FESEM, EDS and XPS were hired for the characterization of ZnO-SiO2 nanohybrid system and applicability of GMZnO–Si mortar was investigated against microbial species (E. coli, S. aureus, A. niger). MIC/MBC/MFC values, agar plating, Inner permeability assay and ROS generation results exhibited excellent mechanistic approaches, by showing its ability to resist the biogenic degradation. The mechanical and durability activities of the GMZnO–Si are found considerably higher in respect to conventional control samples. The experimental outcomes propose a promising way to inclusion of ZnO-SiO2 modified geopolymer for biodeterioration-resistant structure with significant mechanical properties in near future. 

Polymer nanocomposites: Problems, preparation, mechanical properties

Stoyko Fakirov

Advanced Materials Letters, 2018, Volume 9, Issue 6, Pages 400-405
DOI: 10.5185/amlett.2018.1850

The main target of this review article is to try to find the reasons for the drastic difference between expected and observed mechanical properties of polymer nanocomposites prepared via blending the matrix and the nano-reinforcement. Additional target is to recommend thereafter ways for solving of this problem. Based on the published materials the conclusion is drawn that the main reason for this discrepancy is the poor dispersion resulting in formation of particles with sizes in the micrometer but not in nanometre range. For this reason, it is assumed further that these nanocomposites hardly exist. Since currently are missing techniques and instrumentation for a proper dispersion of the reinforcement to single nanoparticles, it is recommended to avoid the dispersion step during manufacturing of polymer nanocomposites. Two techniques are described for this purpose, representing application of the rather new concept of “converting instead of adding” for preparation of polymer nanocomposites. Copyright © 2018 VBRI Press.

Isothermal aging characteristics of rare earth magnesium hexaaluminate based advanced thermal barrier coatings

Premanshu Jana; Santanu Mandal;Koushik Biswas; Ponnarassery S Jayan

Advanced Materials Letters, 2018, Volume 9, Issue 5, Pages 375-382
DOI: 10.5185/amlett.2018.1674

The isothermal aging characteristics of rare earth magnesium hexaaluminate (REMHA) based thermal barrier coatings (TBC) such as lanthanum magnesium hexaaluminates (LMHA), Neodymium doped LMHA (LNMHA) and LNMHA-Yttrium aluminium garnet (YAG) composite were evaluated at 1400 °C and compared with standard yttria stabilized zirconia (YSZ) coating. The platelet structure of hexaaluminate forms meso-porous structure and provides superior sintering resistance than YSZ coating. Faster grain growth kinetics is observed in YSZ coating as compared to hexaaluminate-based coatings. As a result, the mechanical properties of YSZ coating deteriorate severely whereas hexaaluminate based coating remains almost unaltered. The LNMHA coating is found to be the best sintering resistance among them. LNMHA and LNMHA-YAG composite have potential to meet the requirement of advanced TBC operating even at 1400 °C. 

Effect of the incorporation of a microencapsulated healing agent in an epoxy-amine fiber reinforced composite material

Julieta Guti

Advanced Materials Letters, 2017, Volume 8, Issue 11, Pages 1065-1071
DOI: 10.5185/amlett.2017.1550

The objective of this work was to study the effect of incorporating a microencapsulated healing agent in an epoxy matrix and E-glass fiber reinforced composite. Microcapsules were prepared via oil-in-water emulsion polymerization method with dicyclopentadiene as core material and poly(urea-formaldehyde) (PUF) as shell material. The suitable formulation for the epoxy matrix was selected based on the study of the rheological and mechanical properties of various chemical systems. Different amounts of microcapsules were incorporated and the most appropriate processing method (mixing, curing and post-curing cycle) was evaluated. Furthermore, flexural and fracture tests were carried out and the distribution of the capsules as well as the interfacial adhesion with the epoxy matrix were studied. Finally, the processing of fiber reinforced composites, with and without microcapsules, was carried out by compression molding and the mechanical properties of the composites were studied (modulus and maximum flexural strain) from testing three-point bending. The resulting samples with 32 wt. % of fibers and matrices with no microcapsules were compared. Compression molding technique did not affect the integrity of the microcapsules inside the composites. 

Research of plastic and wood raw wastes recovery

Peter Kri

Advanced Materials Letters, 2017, Volume 8, Issue 10, Pages 983-986
DOI: 10.5185/amlett.2017.1587

The main aim of this paper is to present the research findings regarding the recovery possibilities of plastic and wood raw wastes. One of the recovery possibilities for mentioned raw materials is production of waste raw materials based wood-plastic composites (WPC). Lonely production process is influenced by technological and raw material parameters (type of raw material and particle size) and thus the final quality and mechanical properties of WPCs have to be determine. This paper also presents the results of realized experimental research which dealt with the determination of relationship between material parameters and mechanical properties during production of WPCs. The main goal of presented paper is to determine the mutual interaction between mechanical properties, type of the plastic matrix used in WPC, wood/plastic concentration ratio and particle size of wood sawdust used in WPC. In this paper the authors also comparing mechanical properties of WPCs based on recycled and original plastics. As a plastic matrix 100 % original HDPE and recycled HDPE originating from lids of PET bottles was used. Obtained research findings can be very helpful at WPCs production and shown the possibility of using also waste raw materials for WPC products, and thus increase the environmental responsibility with the environment protection.

Impregnation of kraft paper support with polylactic acid multilayers

Sandra Rivero; Javier Lecot; Adriana Pinotti

Advanced Materials Letters, 2017, Volume 8, Issue 6, Pages 741-751
DOI: 10.5185/amlett.2017.7107

PLA coating on Kraft paper is very promising systems for food packaging, and has potential environmental advantages over conventional synthetic paper coatings. This work was focused on: (i) analyzing the physicochemical, thermal and microstructural properties of PLA films; (ii) developing and studying multilayer systems obtained by impregnation of Kraft paper with different layers of PLA solution; (iii) evaluating the influence of PLA layers on the support cellulosic properties. The PLA coating improves packaging material performance and hence the functional properties of Kraft paper. The impregnation of hygroscopic materials as the Kraft paper with PLA was an alternative interesting to obtain more hydrophobic matrices. The assembled materials attained were heat-sealed. Furthermore, the use of PLA adds to potential food applications, a renewable resource value obtained from sources agricultural. The design of this multilayer support also allows its extension to other media such as paperboard. Moreover, the addition of 4 or 5 layers favourably modified the assembled system properties. Increasing even further the number of PLA layers, system properties hardly underwent a significant improvement. Consequently, the selection of the number of PLA layers would be a response to a relationship of commitment between the increase in the cost and the enhancement of the properties.

Impact of 1% gold’s and copper’s addition on mechanical and corrosion properties of resorbable Mg-based metallic glasses

Ryszard T. Nowosielski; K. Cesarz-Andraczke

Advanced Materials Letters, 2017, Volume 8, Issue 5, Pages 614-619
DOI: 10.5185/amlett.2017.7062

In the paper the investigations’ results of the Mg69Zn25Ca5Cu1 and Mg69Zn25Ca5Au1 metallic glasses in the range corrosion mechanical, thermal and structural properties were presented. The results were obtained from compression tests, immersion and potentiodynamic corrosion tests, DTA, XRD. The bulk metallic glasses’ samples for investigations, in the form of rods, were produced by pressure casting. By the way of samples’ manufacturing the GFA (glass forming ability) of the alloys was determined. The gold’s and copper’s additions influence, first of all, for corrosion’s properties, decreasing of corrosion’s rate and increasing compression strength, in comparison with properties of resorbable Mg-Zn-Ca metallic glasses. After two hours of immersion the corrosion’s rate of the Mg69Zn25Ca5Cu1 and Mg69Zn25Ca5Au1 metallic glasses on the level 1,68 mm/year and 0,93 mm/year respectively, were determined. On account of lower corrosion’s rate and neutral impact for human body of the gold, the alloy with gold’s addition may be used as a resorbable material for medical implants.

Multifunctional Inorganic-organic Hybrid Resins With Polymerizable Methacrylate Groups For Biomedical Applications; Effects Of Synthesis Parameters On Polymerisation Shrinkage And Molecular Weight

C. Vibha; P. P. Lizymol

Advanced Materials Letters, 2016, Volume 7, Issue 4, Pages 289-295
DOI: 10.5185/amlett.2016.6046

Inorganic-organic hybrid resins revolutionarize the biomedical field by virtue of its versatility. In this work, bioactive inorganic-organic hybrid resins containing mixture of alkoxides of calcium/magnesium/zinc with polymerizable tetramethacrylate groups was synthesized using 1,3-bis methacryloxy 2-(trimethoxy silyl propoxy) propane as the precursor. We optimised the processing parameters by investigating the influence of pH of the medium used for the hydrolysis of silane on molecular weight of the resultant resin obtained. Physico-mechanical properties including polymerisation shrinkage of photocured composites prepared from novel inorganic-organic hybrid resins were evaluated and compared. The resin hydrolysed at pH 2 have low molecular weight with high filler loading capacity (325 phr) than the one hydrolysed at pH 10.  Photocured polymeric composite fabricated from resin hydrolysed at pH 2 showed lower polymerisation shrinkage, better depth of cure, good diametral tensile strength, non-cytoxic to L929 fibroblasts with good cell viability and cell adhesion. This new biocompatible polymer with low polymerisation shrinkage stands as a potent candidate in biomedical applications, especially in the field of dental, orthopaedic and coating applications. 

Poly(o-anisidine) Carbon Fiber Based Composites As An Introductory Material For EMI Shielding      

Rakesh Kumar; Seema Joon; Avanish P. Singh; Brij P. Singh; S. K. Dhawan

Advanced Materials Letters, 2015, Volume 6, Issue 9, Pages 803-809
DOI: 10.5185/amlett.2015.5915

In response to the striking research activity and publications in fabrication of multifunctional materials, the present work is an attempt to fabricate processible composite sheets of poly (o-anisidine)-carbon fiber (PoACF) by a facile, low cost method and find their use in electromagnetic interference (EMI) shielding in X-band (8.2-12.4 GHz).  PoACF composite is synthesized by in-Situ oxidative emulsion polymerization and transformed into thin sheets by compression molding technique using different ratio of phenolic novolac resin as a binder. The prepared PoACF composites and sheets are characterized by SEM, TGA, UV-vis, & FT-IR techniques. PoACF sheets have conductivity of the order of 10 -3 to 10 -1 S/cm and maximum shielding effectiveness of 32.57 dB at 4 mm thickness. These sheets have flexural strength between 18.82 to 41.28 MPa. The sheets of PoACF composite have sufficient thermal as well as mechanical stability and may be accepted as an economical material for EMI shielding application.

 Effect Of Nanoclay On The Toughness Of Epoxy And Mechanical, Impact Properties Of E-glass-epoxy Composites

K. Krushnamurty; I. Srikanth; B. Rangababu; S. K. Majee; R. Bauri; Ch. Subrahmanyam

Advanced Materials Letters, 2015, Volume 6, Issue 8, Pages 684-689
DOI: 10.5185/amlett.2015.5817

Organically modified montimorillonite nanoclay was added to the epoxy and E-glass-epoxy composites. The influence of nanoclay content (varied between 0 to 5wt %) on the relative crosslink density and the fracture toughness of the epoxy matrix was studied. Differential scanning calorimetry (DSC) indicated that the amino functional groups present on the nanoclay react with the epoxy matrix to increase the crosslink density of about 13 and 18% at 3 and 5wt% addition, respectively. The toughness of the epoxy composites increased by 25% at 3wt% addition of nanoclay, whereas, it decreases at 5wt%. Flexural strength and tensile strength of the E-glass-epoxy composites were found to increase by 12% and 11% respectively at 3wt% addition of nanoclay, while at 5wt% addition these properties decreased due to the matrix embrittlement.  Interestingly matrix embrittlement is found to be beneficial in increasing the impact resistance due to spallation of embrittled matrix that ensures the dissipation of the impact energy. 5wt% nanoclay addition increases the impact strength by 29% and reduces the back face bulge of composite by 31%. These results may lead to the design and realization of glass-epoxy composites with better impact strength.

How Ethanol Treatment Affects The Physico-chemical And Biological Characteristics Of Silk Fibroin Nanofibrous Scaffolds

Mazaher Gholipourmalekabadi; Masoud Mozafari; Mojgan Bandehpour; Marzieh Sameni; Hossein Ghanbarian

Advanced Materials Letters, 2015, Volume 6, Issue 5, Pages 391-394
DOI: 10.5185/amlett.2015.5739

In this study, the effects of ethanol treatment on the mechanical and biological characteristics of the nanofibrous silk fibroin (NSF) scaffolds were evaluated. The results obtained from the mechanical tests confirmed that ethanol treatment significantly enhanced the physical properties of the scaffolds through the formation of a ß-sheet structure. It was shown that the ethanol treatment increased the mechanical property and cell viability, while decreased the porosity of the randomly arranged uniform nanofibers. The ultimate tensile strength for the NSF and ethanol-treated NSF (ET-NSF) scaffolds were 0.76 and 1.33 MPa, respectively. In addition, the ethanol treatment positively affected the proliferation rate of rat bone-marrow stromal cells (rBMSCs) without any detectable cytotoxicity. All the results obtained from this study strongly indicated the efficacy of ethanol treatment in enhancement of mechanical and biological characteristics of silk fibroin nanofibrous scaffolds.

Solvent Free, Efficient, Industrially Viable, Fast Dispersion Process Based Amine Modified MWCNT Reinforced Epoxy Composites Of Superior Mechanical Properties

Bhanu Pratap Singh; Veena Choudhary; Satish Teotia; Tejendra Kumar Gupta; Vidya Nand Singh; Sanjay Rangnath Dhakate; Rakesh Behari Mathur

Advanced Materials Letters, 2015, Volume 6, Issue 2, Pages 104-113
DOI: 10.5185/amlett.2015.5612

Dispersion of multiwalled carbon nanotubes (MWCNTs) into epoxy resin is a challenging task for the process to be viable on industrial scale. Herein, amine functionalized MWCNTs (Am-MWCNTs) were reinforced into epoxy resin using industrially viable, fast, efficient, solvent free, high speed homogenizer dispersion technique. Am-MWCNTs ranging from 0.1 to 0.75% by w/w were loaded in epoxy and the effects of loading of Am-MWCNTs on mechanical properties of epoxy composites are investigated. The flexural strength of Am-MWCNTs based epoxy composites reached up to 163 MPa for 0.5 wt% MWCNTs loaded sample compared to 95 MPa for pure cured epoxy sample; an overall improvement of 72% in the flexural strength. In addition to this, the flexural modulus value reached to 3795 MPa for 0.75 wt% Am-MWCNTs loaded sample from 2250 MPa for pure epoxy sample, an improvement of 69%. The enhancement in the mechanical properties was correlated with the dynamic scanning calorimeter results, TEM and SEM images of fractured surface. The substantial improvement in the mechanical properties of the epoxy resin at such low CNT loading can open a venue for the preparation of structurally strong structures for aerospace, defence, automobile and sports industries.

Modified Arcan Tests For Concrete With Multi-walled Carbon Nanotubes

Siddik Sener; Yasin Caglar; Cagatay M. Belgin; Kadir C. Sener

Advanced Materials Letters, 2014, Volume 5, Issue 8, Pages 429-434
DOI: 10.5185/amlett.2014.amwc1032

An experimental study consisting 70 tests have been conducted to study the influence of addition of reinforcing fibers on concrete specimens. The experimental program included concrete specimens that were tested with modified Arcan test machine with different notch lengths. The reinforcing effect of highly dispersed multi-walled carbon nanotubes (MWCNTs) in concrete has been investigated. The results revealed that inclusion of CNTs in the design mix improve both the tensile fracture characteristics and compressive strength when not mixed with a surfactant compound. The improvement in the mechanical properties specimens with the addition of CNTs are observed more clearly with increasing curing age. The mixing process to achieve uniformly dispersed and properly mixed mortar however requires specialized equipment, such as ultrasonic mixers. The results also indicated some dependency on the size of the specimens, which is a well known phenomenon that is observed for brittle heterogenous materials such as concrete.

Improving The Mechanical And Thermal Properties Of Semi-coke Based Carbon/copper Composites Reinforced Using Carbon Nanotubes

S. Kumari; A. Kumar; P. R. Sengupta; P. K. Dutta; R. B. Mathur

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 265-271
DOI: 10.5185/amlett.2013.10546

Multiwalled carbon nanotubes (MWCNT)- reinforced carbon/copper (C/Cu) composites were developed by powder metallurgy technique and mixed powders of C and Cu were consolidated into plates without using any extra binder followed by sintering at 1000 o C in inert atmosphere. Samples were characterized for structural, mechanical, electrical and thermal properties w.r.t. different mass fraction of MWCNT in C-Cu matrix. In comparison to C/Cu composite, addition of minute amount (0.25 wt%) of CNT in C-Cu substantially improved the mechanical, electrical and thermal properties of composites. These composites were mechanically stable and strong and exhibited high bending strength of 162 MPa, indicating a homogeneous dispersion of MWCNTs in the C-Cu matrix. Maximum thermal conductivity of 37.60 W/mK perpendicular to the pressing direction was obtained for 0.50 wt% CNT reinforced C-Cu composite exhibiting an improvement of 45% over pure C-Cu composite processed under identical conditions. High thermal conducting and mechanically strong composites can be used as heat sink for long time.

Variation In Mechanical Properties With Substrate Temperature Of SbTi Thin Film Deposited By RF Sputtering Technique

A. Rambabu; Anil Tumuluri; K.C. James Raju

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 292-296
DOI: 10.5185/amlett.2013.fdm.12

Nanoindentation technique has been used to determine the mechanical properties of bismuth layered structure ferroelectric thin films, which have been shown to be promising for MEMS based devices used in sensing, actuation and energy harvesting, especially at elevated temperatures. SBTi (SrBi4Ti4O15) is a promising layered ferroelectric material and thin films of this composition are deposited on amorphous fused silica substrates by rf sputtering technique varying the substrate temperature from 600–725 o C. The crystal structure and surface morphology of SBTi thin films are characterized by X-ray diffraction and atomic force microscopy. Depth- sensing nanoindentation system is used to measure the mechanical characteristics of SBTi thin films. Nanoindentation measurements reveal that the Young’s modulus and hardness of SBTi thin films are related with grain size and crystal orientation which in turn depend on substrate temperature. The increase in mechanical properties with grain size is observed, indicating the reverse Hall-Petch effect. Furthermore, hardness and Young’s modulus of the (119) oriented films were higher than those of (0010) oriented films. The tribological properties of these films are confirmed by performing the scratch tests on the same films.

Mechanical Properties Of Multifunctional Epoxy  resin/glass Fiber Reinforced Composites Modified  with Poly(ether Imide)

Jagrati Kandpal; Samar B. Yadaw; Arun K. Nagpal

Advanced Materials Letters, 2013, Volume 4, Issue 3, Pages 241-249
DOI: 10.5185/amlett.2012.8403

In the present paper effect of thermoplastic on various mechanical and thermal properties of multifunctional epoxy resin have been studied. Epoxy phenol novolac resin has been cured with hardner diamino, diphenyl sulfone. Changes in mechanical and thermal properties of epoxy phenol novolac resin with engineering thermoplastic poly (ether imide) have been investigated. Specimens were prepared using different mixing orders for multifunctional epoxy resin with poly (ether imide). Effect on glass transition temperature (Tg) were observed by using DSC measurements. Variation in mechanical properties viz. Tensile strength, flexural strength, flexural modulus, interlaminar shear strength and impact strength have been observed. With the thermoplastic modification of thermoset matrix material, improvement in mechanical properties of epoxy-glass fiber reinforced composites have been expected. Changes in storage modulus and loss modulus of all specimens were also evaluated by dynamic mechanical analysis (DMA). Scanning electron microscopy (SEM) was used to investigate the relationship between the morphological study of the fractured epoxy resins and mechanical properties of the modified epoxy resins and glass fiber reinforced composites. If the polymer matrix is fairly brittle (unmodified epoxy), there may be a corresponding reduction in mechanical properties. Incorporation of engineering thermoplastic Poly (ether-imide) has resulted in improvement of above stated mechanical properties. All results indicated that thermoplastic modified multifunctional epoxy resin proved to be a good matrix material which enhances the mechanical properties of glass fiber reinforced composites.

Sunn hemp cellulose graft copolymers polyhydroxybutyrate composites: morphological and mechanical studies

Susheel Kalia; Anil Kumar; B.S. Kaith

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 17-25
DOI: 10.5185/amlett.2010.6130

For the synthesis of biocomposite materials for useful applications, it becomes necessary to modify the surface of natural fibers through chemical treatments. Morphology, structure and properties of natural fibers have an obvious effect on the mechanical properties of the biocomposite materials. It is thus necessary to know the morphology, thermal stability and crystalline behavior of original and modified fibers. In present paper, sunn hemp fibers (SHF) were chemically modified with ethyl acrylate and binary monomers (EA+MMA, EA+AA) through microwave radiations induced graft copolymerization. Various reaction parameters were optimized to get maximum grafting (91.8%). Morphology, thermal stability and crystalline behavior of original and modified fibers were investigated. Morphological and thermal studies showed that surface of sunn hemp fibers becomes rough and amorphous through graft copolymerization and thermal stability has been found to be increased. Microwave radiation induced grafting showed a diminutive effect on the crystalline behavior of the sunn hemp fibers as optimum time to get maximum grafting is very less (40 min) in comparison to conventional grafting. Synthesized graft copolymers were used as reinforcing material in preparation of polyhydroxybutyrate biocomposites. It has been observed that graft copolymers improved the interface between fiber and matrix and enhanced the mechanical strength of composites.