Morphology, Rheological and Mechanical Properties of Isotropic and Anisotropic PP/rPET/GnP Nanocomposite Samples

The effect of graphene nanoplatelets (GnPs) on the morphology, rheological, and mechanical properties of isotropic and anisotropic polypropylene (PP)/recycled polyethylene terephthalate (rPET)-based nanocomposite are reported. All the samples were prepared by melt mixing. PP/rPET and PP/rPET/GnP isotropic sheets were prepared by compression molding, whereas the anisotropic fibers were spun using a drawing module of a capillary viscometer. The results obtained showed that the viscosity of the blend is reduced by the presence of GnP due to the lubricating effect of the graphene platelets. However, the Cox–Merz rule is not respected. Compared to the PP/rPET blend, the GnP led to a slight increase in the elastic modulus. However, it causes a slight decrease in elongation at break. Morphological analysis revealed a poor adhesion between the PP and PET phases. Moreover, GnPs distribute around the droplets of the PET phase with a honey-like appearance. Finally, the effect of the orientation on both systems gives rise not only to fibers with higher modulus values, but also with high deformability and a fibrillar morphology of the dispersed PET phase. A fragile-ductile transition driven by the orientation was observed in both systems.

Evaluation of geotechnical properties, petrographic characteristics and ultrasonic wave velocity of weak sandstones

Several new settlements have been constructed in the desert areas of Egypt. These new settlements are composed of many new types of problematic formations that creating many geological and engineering challenges. One of the most problematic formations is weak sandstones that are characterized by low mechanical strength and bearing capacity as well as high deformability and fracturing. The physico-mechanical characteristics of these sandstones are the most crucial parameters in design and stability evaluation of any surface and underground engineering structures. The determination of these parameters is complicated, difficult and time consuming as well as is required a great accuracy in sample preparation and testing procedure, and is considered as expensive testing. The objective of this study is analyzing the shallow marine weak sandstones to determine the best and significant correlations of petrographic characteristics and physical engineering index properties that may be useful for estimating unconfined compressive strength (UCS), uniaxial pore volume compressibility (mv), compressional P-wave velocity (Vp) and dynamic constrained modulus (Es). As well as predicting the UCS and mv from compressional P-wave velocity test and estimating the petrographic parameters from the physical engineering index parameters. The present study revealed that the studied samples are high to very high porous sandstones with very low to moderate density, and classified as extremely weak to weak rocks with very high deformability and very low wave velocity. In this study, the physical properties form non-significant linear relations with UCS, Vp, and Es as well as there are moderately strong to strong correlations between P-wave velocity, constrained modulus, unconfined compressive strength and compressibility characteristics. Based on the regression analysis, the dolomite cement and matrix contents, quartz and rock fragments contents, packing density and proximity, sorting, roundness, mean grain size, and grain to cement contact exhibited weak to strong statistical correlations with mechanical properties of the studied sandstones. These relationships revealed that due to the mineralogical, textural, and microstructure variations of the studied recycle origin sandstones, the non-significant to significant relations are resulted. In this study, the backward multiple regression was applied to predict the UCS, mv, Vp and Es of the studied sandstones by selecting some physical and petrographic characteristics which exhibit statistically significant correlations with them. The results of this study were presented in the form of predictive models and equations.

Simulation of Process Rolling Plates from Alloy of Al-Mg System Economically Doped with Scandium

The modes of hot and cold rolling of plates from an alloy of the Al-Mg system alloy, doped with scandium in the range of 0.10-0.12%, are modeled. At the first stage of work, using the DEFORM-3D software package, we simulated the process of hot sheet rolling at the Quarto 2800 mill, in order to obtain a billet for further cold rolling. Analysis of the simulation data showed that with the adopted compression mode, the metal forming and temperature conditions of rolling make it possible to obtain plates up to 45 mm thick, without defects, with rational power loading of the equipment. Further modeling of the regime of cold rolling of plates with a thickness of up to 31.5 mm showed that cold rolling can be carried out in 4 passes, provided that the stress and rolling force do not exceed the permissible values. At the second stage of work, we conducted an experimental verification of the obtained simulation results both in industrial and in laboratory conditions. It was found that the value of the total compression leading to the destruction of the samples, depending on the rolling conditions, should not exceed 21-30%. At this degree of deformation, the rolled metal from the alloy under study has high strength and plastic properties. Subsequent industrial verification of the research results confirmed that this alloy is quite advanced technologically, while it has high deformability, both during hot and cold rolling, which allows us to recommend it for sheet deformed semi-finished products in the manufacture of structural products for various purposes.

Physicochemical modification of heat-shrinkable epoxy polymers

An approach to the physicochemical modification of heat-shrinkable epoxy-diane polymers was considered, these polymers being used as couplings for the repair of polymer pipelines for various functional purposes. The purpose of the modification is to stabilize and improve the performance of the end couplings that are heat-shrinkable. We assessed the prospects of preparation of the products of various profiles by forming cross-linked polymers in a highly elastic state by plunger extrusion via creating favorable conditions for the orientation of interstitial fragments in epoxy-diane polymers. The starting epoxy-diane composition contained rigid and elastic components. The polymers fabricated by hardening of these compositions have both a glass transition temperature, which is convenient for operation, and high deformability in glassy and highly elastic states. We investigated the tensile strength, the elastic modulus, the failure deformation and the flaring deformation of the inner diameter of the preform of epoxy-diane polymers. Physical modification of a liquid filled epoxy-diane composition before mixing with a hardener was performed by using low-frequency ultrasonic treatment. We analyzed the results associated with the effect of combined ultrasonic treatment on the physical-mechanical and service properties of heat-shrinkable epoxy-diane polymers filled with short glass fibers.

Hysteresis modeling and feedforward compensation of a flexible structure actuated by macro fiber composites using bias bipolar Prandtl-Ishlinskii model

As a novel fiber-based piezoelectric composite material, macro fiber composites (MFC) affords notable advantages of good flexibility, high deformability, and large actuation ability. However, the intrinsic hysteresis behavior of the MFC decreases the positioning precision and performance of the flexible structure actuated by MFC actuators. A bias bipolar Prandtl-Ishlinskii (BBPI) model is presented to describe the bias bipolar hysteresis nonlinearity of a MFC-actuated flexible cantilever. The BBPI hysteresis model is composed of two parts: a superposition of the weighted play operators of the classical Prandtl-Ishlinskii (PI) model is employed to characterize the symmetric hysteresis. And a superposition of the weighted dead-zone operators is cascaded to deal with the bias bipolar behavior. Experimental identification results demonstrate that the presented BBPI model exhibits better modeling performance than the classical PI model. A feedforward compensation strategy based on the inverse BBPI hysteresis model is proposed. Experiments on trajectories tracking subject to a triangular wave, sinusoidal wave, and triangular wave with random amplitudes are carried out. Experimental results demonstrate the feasibility and effectiveness of the proposed BBPI model and the inverse feedforward compensator.

Fabricating Elastomeric Photomask with Nanosized-Metal Patterns for Near-Field Contact Printing

When an elastomeric photomask is used for near-field contact printing, the high deformability of the elastomer mask plate enables gap-free full contact with the substrate, minimizing the effect of diffraction. This image-transfer technique provides sub-50 nm resolution and depth-of-focus-free lithographic capability with cost-efficient equipment. However, the method’s application is limited due to the lack of a wellestablished protocol for fabricating a nanoscale mask pattern on an elastomeric substrate, which remains a major technical challenge in the field of near-field contact printing. In this study, we present a reliable protocol for fabricating a metal-embedded polydimethylsiloxane (PDMS) photomask. Our fabrication protocol uses conventional nanofabrication processes to fabricate nanosized chromium mask patterns and then transfers the chromium patterns to an elastomeric mask plate using a sacrificial Ni layer. Our protocol provides a high flexibility mask pattern design, and highly stable metal patterns during transferring process. By careful optimizing the experimental parameters, we determined a perfect pattern transfer ratio, which avoided any mechanical failure of the metal pattern, such as debonding or wrinkling. We then fabricated a PDMS photomask and confirmed its nanoscale patterning resolution, with the smallest feature 51 nm in width under a 400-nm light source. We anticipate that our fabrication protocol will enable the application of cost-efficient and high-resolution near-field photolithography.

Self-compacting concrete as a modern solution to small architectural forms

Modern Materials science in Сonstruction is developing in a way of higher functionality, durability, ecological safety of the materials, which also must be easy to work with. The workability of concrete is provided by its property to fill the formwork under the influence of gravity. Small architectural forms (SAF) – are practical and art objects which complement outdoor spaces and enrich architectural, urban and landscape composition of the city. Manufacturing of SAF is complicated by its extraordinary geometric shapes with plenty of tiny elements. This fact limits the usage of traditional technologies of vibration for compaction. In this paper properties and composition of self-compacting concrete (SCC) are discussed, as well as the possibility of its application for thin-walled heavily reinforced constructions to produce unique SAF for landscape design. The obtaining of flowable segregation-resistant concrete mix with low water-cement ratio is studied. The hypothesis of applicability of SCC for SAF in landscape design is based on high deformability, flowability and consolidation by means of its own weight without segregation. The methodology of the research is based on the literature review concerning the usage of SCC for SAF with some special additives with plasticizing and anti-segregating affects. The investigation showed that SCC is applicable for SAF in landscape design.

Pushover Response of Multi Degree of Freedom Steel Frames

Seismic codes use the behaviour factor to consider the ductility and the structure's non-linearity to improve the system's overall performance. Generally, Steel moment-resisting frames are characterized by a relatively high period showing high deformability and, foreseen that with stringent damageability criteria, the adopted behaviour factor might not optimally be utilized for achieving better performance of the frames. The design is generally governed by stiffness, leaving behind a complex structural system where the capacity design rules are disturbed and therefore necessitates to relax the drift limits for such frames. Given this and with extensive parametric analysis, the current paper aims to examine the behaviour factor of steel Moment Resisting Frames (MRFs). The parametric analysis has been conducted on rigid steel MRFs of 9, 7, and 5 storeys with bay 4 different bay widths of 9.15 m, 7.63 m, 6.54 m, and 5.08 m. Perimeter frame configuration has been designed using 4 different behaviour factors (q = 6.5, 4, 3, and 2) for a total number of 144 cases. Static nonlinear analysis has been conducted, and consequently, the behaviour factors have been examined. It has been observed that compatibility is required while choosing the drift limit for an assumed ductility class of the code. Doi: 10.28991/cej-2020-SP(EMCE)-08 Full Text: PDF

Open Porous α + β Titanium Alloy by Liquid Metal Dealloying for Biomedical Applications

Open porous dendrite-reinforced TiMo alloy was synthesized by liquid metal dealloying of the precursor Ti47.5Mo2.5Cu50 (at.%) alloy in liquid magnesium (Mg). The porous TiMo alloy consists of α-titanium and β-titanium phases and possesses a complex microstructure. The microstructure consists of micrometer scale β-titanium dendrites surrounded by submicrometer scale α-titanium ligaments. Due to the dendrite-reinforced microstructure, the porous TiMo alloy possesses relatively high yield strength value of up to 180 MPa combined with high deformability probed under compression loading. At the same time, the elastic modulus of the porous TiMo alloy (below 10 GPa) is in the range of that found for human bone. This mechanical behavior along with the open porous structure is attractive for biomedical applications and suggests opportunities for using the porous TiMo alloy in implant applications.

Effect of Cooling Process on Microstructure Especially Precipitation Behavior of High-Strength Pipeline Steel

The effect of different cooling processes on microstructure especially precipitation behavior and properties of high grade pipeline steel was investigated in this paper. The results showed that: By two stage controlled cooling process, ferrite-bainite phase was obtained in X80 pipeline steel with high deformability, the average size of Martensite and Austenitic islands (M/A) was approximately 1μm, the Uniform Elongation (UEl) was 10%. Whereas granular bainite was obtained after conventional laminar cooling process and fine M/A of 1∼2μm size dispersed in grains or along grain boundaries. Compared with conventional pipeline steel, high deformability pipeline steel through two stage controlled cooling process had higher Elongation (El), impact toughness and lower yield ratio, due to the existence of ferrie+bainite phase structure which reduced yield strength (YS) and enhanced deformation performance and fracture toughness. Additionally, the effect of precipitation strengthening of high grade pipeline steel produced by Ultra-fast cooling (UFC) process was superior to that produced by conventional laminar cooling process. A significant amount of nano particles precipitated with the size of 1nm to 5nm were obtained through the UFC process. The application of UFC made the precipitation process avoid the nose temperature of precipitation temperature time (PTT) curve, thus the size of nano particles were smaller and the distribution of precipitation was more dispersive.