Composite Materials and Structures

Polymer-based matrix hybrid composites meet their demand in various engineering applications and food industries due to their excellent mechanical, thermal, corrosion, and biodegradable performance. The polymer-based hybrid composites have been a better choice for high thermal insulation at low cost. This experiment attempted to find the thermal adsorption characteristics, heat deflection temperature, linear thermal expansion, and thermal conductivity of epoxy hybrid composites, which contained four different layers of Kevlar and basalt fiber fabricated via a low-cost conventional hand mold layup technique. This experiment revealed that the effect of basalt/Kevlar fiber on epoxy increased thermal performance. The results noted that the hybrid composite consists of less Kevlar fiber with the maximum basalt fiber of sample 4, showed excellent thermal adsorption effect on weight loss limited at 70.98%, and a better heat deflection temperature and 11.78 × 10 − 6 per °C linear thermal ex...

Steel fly ash silos are critical components of industrial plants, particularly in the cement and power generation industries, where fly ash is stored for further use or disposal. Due to their height, large mass, and storage capacity, these structures are subjected to various forces, with seismic conditions being one of the most significant considerations for their stability. This paper explores the impact of seismic conditions on steel fly ash silos, focusing on design considerations and guidelines as per IS 1893:2024, which provides the criteria for seismic design of structures in India.

Phosphate treatments for conservation of stone have provided so far encouraging results in laboratory studies, as they exhibit good effectiveness, compatibility and durability to accelerated weathering tests. However, limited data are available about their long-term performance in real environment. Here, a systematic evaluation of phosphate consolidants after prolonged exposure in the field is reported for the first time. Naturally weathered marble specimens and a XVII century marble sculpture located in the Park of the Royal Palace in Versailles were treated by various formulations of the phosphate consolidant. Their conservation state was assessed before treatment by non-destructive methods (ultrasounds, color measurement, water absorption) and, in the case of the specimens, also by slightly destructive tests (SEM, FT-IR, MIP, IC). The conservation state of the specimens and the sculpture was further assessed right after treatment and then periodically monitored during exposure in...

Working Group 1 of RILEM TC 238-SCM 'Hydration and microstructure of concrete with supplementary cementitious materials (SCMs)' is defining best practices for the physical and chemical characterization of SCMs, and this paper focusses on their thermal analysis. Thermogravimetric analysis (TGA) can provide valuable data on the chemical and mineralogical composition of SCMs. Loss-on-ignition (LOI) testing is a commonly used, standardized, but less sophisticated version of TGA that measures mass at endpoints only, with heating generally in air. In this paper we describe the use of TGA and LOI to characterize Portland cement with limestone additions, coal combustion fly ashes, ground-granulated blast furnace slag, calcined clays, and natural pozzolans. This paper outlines the value and limitations of TGA and LOI (in the formats

The reaction kinetics of the alkali silica reaction depends on the composition of the pore solution. The evolution of the pore solution composition in different cement pastes and concretes was studied. Pastes containing silica fume or metakaolin had the lowest amount of alkalis in the pore solution. In addition, metakaolin increased the aluminium concentrations. The lowest expansion was measured for the concretes made of blended cement pastes with low alkali and hydroxide content in their pore solution, for the duration of the present study, no additional aluminium effect was observed due to the already low pH. Addition of 400 mM of Li slowed down expansion rate of concrete prisms at 40 and 60 °C, however, similar expansion was observed for samples with and without Li at 60 °C after 1 year. Temperature, alkali concentration and pH of pore solution all have a major effect on ASR expansion.

The reaction kinetics of the alkali silica reaction depends on the composition of the pore solution. The evolution of the pore solution composition in different cement pastes and concretes was studied. Pastes containing silica fume or metakaolin had the lowest amount of alkalis in the pore solution. In addition, metakaolin increased the aluminium concentrations. The lowest expansion was measured for the concretes made of blended cement pastes with low alkali and hydroxide content in their pore solution, for the duration of the present study, no additional aluminium effect was observed due to the already low pH. Addition of 400 mM of Li slowed down expansion rate of concrete prisms at 40 and 60 °C, however, similar expansion was observed for samples with and without Li at 60 °C after 1 year. Temperature, alkali concentration and pH of pore solution all have a major effect on ASR expansion.

Water penetration in porous building materials can cause damage in building components exposed to wet environmental conditions. A system to monitor water penetration by means of electrical conductivity measurements is presented (Gummerson et al. Build Environ 15:101-108, 1980). The sensor allows non-destructive and continuous monitoring of different layers of building envelopes with high space and time resolution. Capillary uptake experiments have been performed to assess the reliability of the developed system. Sensors data are compared to the results of the analysis of neutron radiographs taken during the experiments. These sensors are easy to apply in different positions, even deep in the structural components where direct gravimetric investigation is not possible. Electrical conductivity measurements provide a good temporal description of the capillary uptake process, however a calibration for moisture content quantification could not yet be achieved.

In this work, a magnesium stannate-tin oxide nanocomposite (Mg 2 SnO 4 @SnO 2) was prepared using the sol-gel combustion method. The physical properties of the products have been characterized by different analysis techniques. The XRD results revealed the combined structure of the cubic inverse spinel phase of Mg 2 SnO 4 and the tetragonal phase of SnO 2 with a mean crystalline size of 5.1 nm. The average grain sizes of SnO 2 and Mg 2 SnO 4 @SnO 2 from FESEM images were about 51.98 nm and 58.18 nm, and TEM images revealed that the size of nanoparticles were about 30-200 nm and 20-50 nm, respectively. The band gap energy of Mg 2 SnO 4 @SnO 2 NPs was estimated to be about 3.9 eV. Results from FESEM and BET revealed the sample's sponge-like meso/ macroporous morphology. PL spectra have revealed a blue emission. The optical constants of Mg 2 SnO 4 @SnO 2 deposited on the glass substrate were determined using UV-Vis transmittance data and theoretical approaches. The electrochemical performances of the porous Mg 2 SnO 4 @SnO 2 deposited on ITO-coated glass substrate and metal foam (Ni and Cu) substrates as particulate composites by doctor blade technique were compared by GCD, CV, and EIS analysis. The best performance is belonged to the Mg 2 SnO 4 @SnO 2 /Cu foam electrode with a specific capacitance of 675 Fg-1 at a current density of 1 Ag-1. Mg 2 SnO 4 @SnO 2 /Ni foam has a higher capacitance retention rate, which showed stability of 86.27 % over 5000 charge/discharge cycles at a current density of 10 Ag-1 .

The usability of pulsed broadband terahertz radiation for the inspection of composite materials from the aeronautics industry is investigated, with the goal of developing a mobile time-domain spectroscopy system that operates in reflection geometry. A wide range of samples based on glass and carbon fiber reinforced plastics with various types of defects is examined using an imaging system; the results are evaluated both in time and frequency domain. The conductivity of carbon fibers prevents penetration of the respective samples but also allows analysis of coatings from the reflected THz pulses. Glass fiber composites are, in principle, transparent for THz radiation, but commonly with significant absorption for wavelengths >1 THz. Depending on depth, matrix material, and size, defects like foreign material inserts, delaminations, or moisture contamination can be visualized. If a defect is not too deep in the sample, its location can be correctly identified from the delay between partial reflections at the surface and the defect itself.

The results of elemental analysis of 19 glass vessels dating to the early Islamic periods which are kept in the National Museum of Iran are presented in this paper. The samples were discovered during archeological excavations in several Islamic sites. Elemental analysis of these samples is performed by micro-PIXE technique and major and minor elements of these samples are measured. Glass type, raw material used in their production process and colorant of the glasses in diverse sites are investigated and determined based on our results. The results show that almost all glasses found in all sites are high soda-lime-silica glasses. Since the amounts of magnesium oxide and potassium oxide in all analyzed samples except one sample are more than 2.5%, it is clear that the ashes obtained from halophytic plants are considered as supplying source for sodium oxide. Also, our chemical composition results have been combined and compared with the reported results from Iraq, Syria and Egypt. This comparison shows that glass vessels of Iran tend to cluster together in a distinctive group, particularly with regard to their Al 2 O 3 and P 2 O 5 contents.

Este estudio se ha realizado con el objetivo de profundizar en el conocimiento del comportamientode los materiales plásticos y compuestos con matriz polimérica ante situaciones de impacto. Enespecial este PFC estudia los fenómenos de indentación dinámica que ocurren al ...

In the present study an elastic-plastic strain analysis is carried out for fibrous composites by using numerical modeling. Application of homogeneous transversely-isotropic model was chosen based on problem solution of a square plate with a circular hole under uniaxial tension. The results obtained in this study correspond to the solution of fiber model trial problem, as well as to analytical solution. Further, numerical algorithm and software has been developed, based on simplified theory of small elastic strains for transversely-isotropic bodies, and FEM. The influence of holes and cracks on stress state of complicated configuration transversely-isotropic bodies has been studied. Strain curves and plasticity zones that are formed in vicinity of the concentrators has been provided. Numerical values of effective mechanical parameters calculated for unidirectional composites at different ratios of fiber volume content and matrix. Content volume proportions of fibers and matrix defined for fibrous composite material that enables to behave as elastic-plastic body or as a brittle material. The influences of the fibrous structure on stress concentration in vicinity of holes on boron/aluminum D16, used as an example.

The use of polymeric materials to replace metal or wood has become increasingly popular lately in most fields of activity. Specific amounts of reinforcement materials have been included in the structure of these polymeric materials in order to improve their mechanical properties. The increasing popularity of these types of materials was accompanied by the development of different machinery and technologies designed to process them, so as to make them as productive as possible and to achieve inexpensive high performance parts. Natural polyamide 6.6 is a polymeric material noted for its high rigidity, hardness, impact resistance, etc. The reinforcement materials added improve the mechanical properties of this type of material. Our research consisted of a comparative study of the behavior of polyamide reinforced with glass fibers and glass microspheres when subject to different mechanical stresses. The test specimens were processed by injection and relied on an experimental Taguchi pla...

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The use of high-strength concrete (HSC) instead of normal-strength concrete (NSC) in columns has the advantage of allowing the column size to be reduced and is thus becoming popular. However, since HSC is more brittle than NSC, its use could result in undesirable brittle failure. To evaluate the ductility of columns, nonlinear moment-curvature analysis taking into account the stress-path dependence of the steel reinforcement is required. Based on such analysis, a parametric study has been conducted to investigate the effects of various factors on the ductility of columns. The results revealed that the effect of concrete strength is dependent on the axial stress level (axial load to area ratio) and axial load level (axial load to capacity ratio). At the same axial stress level, the use of HSC has little or basically no adverse effect on the ductility but if the same axial load level is maintained to reduce the column size, the use of HSC would significantly reduce the ductility. Finally, two formulas for direct evaluation of the ductility of columns are developed.

The purpose of the study was twofold: (i) develop and test the antimicrobial properties of a polylactic acid-and a polyurethane-based filament, and (ii) use these filaments to manufacture a socket-based prosthesis to verify printability and longevity of the antimicrobial properties. It was hypothesized that the formulation of a novel biocidal copper-based nanocomposite with a biocompatible 3D printing polymer/copolymer can be used for the development of antimicrobial medical devices to mitigate microbial risks during long space flight missions [1, 2, 3]. METHODS: Polylactic Acid-based Filament Development-The development of a polylactic acid-based filament involved several processes, such as fermentation (corn to Lactic Acid), condensation (Lactide) and polymerization (Polylactic acid; PLA). The addition of copper antimicrobial nanocomposite additive to pellets at different concentrations facilitated the development of a multipurpose antimicrobial filament. The addition of a treated carbon fiber and natural fibers nanocomposites our team create a high strength polylactic acid-based filament (Zuniga, 2018). Polyurethane-based Filament Development-The current polyurethane-based filament is a versatile non-toxic biocompatible flexible filament with a wide variety of applications. To confer biocidal activity to this filament, the inorganic copper-based nanocomposite additive was immobilized physically by embedment in the polyurethane-based filament structure. The additive use zeolites as carriers. The metallic ions contained in zeolite are replaced by copper ions with biocidal properties through ionic exchange. The use of nanoparticles effectively increased the concentration of copper within the zeolites maximizing the antimicrobial behavior. The result was a polyurethane-based flexible filament with high biocidal activity, better action spectrum and longer duration. Antimicrobial testing-Antimicrobial effectiveness and longevity of the filaments was tested by an independent laboratory following standard procedures for ISO 22196 before and after a heat-based accelerating aging agent for a period of 1 month equivalent to 1 year period of aging (Situ Biosciences LLC, wheeling, IL, Chicago, USA). The antimicrobial longevity was tested using a heat-based accelerating aging agent (50°C) using a standard oven heat accelerated aging protocol for standard environmental conditions. Six flat test samples (5 cm x 5cm x 1cm) of each material was manufactured and tested. The ISO 22196 is designed to measure the antimicrobial properties of a solid plastic surface incubated with bacteria, such as two strains of Staphylococcus Aureus (Methicillin-resistant and standard strain) and Escherichia Coli. The bacterial analysis showed that both, the acid-and polyurethane-based filaments with 1% antibacterial nanoparticles additives was up to 99.99% effective against two strains of Staphylococcus Aureus (Methicillin-resistant and standard strain) and Escherichia Coli. The materials showed a 98.99% reduction after one year of simulated aging. The printability of the device was similar o standard polylactic acid and thermoplastic polyurethane filaments. The extrusion process did not affect the antimicrobial properties of the filaments [2]. CONCLUSIONS: A recent study [3] found that 28 astronauts experienced an altered immune response during their six-month mission aboard the International Space Station [3]. The direct cause of this altered immune behavior has not been identified, but may be linked to radiation, microbes, stress, microgravity, altered sleep cycles and isolation 1. In a prolonged space mission, these factors could cause increased susceptibility to illness and, in turn, limitations to human space exploration [1, 3]. The unprecedented accessibility of additive manufacturing technology and the development of 3D printing "Active Materials" have several medical applications and have the potential to revolutionize the manufacturing of medical devices. Promising applications include developing medical devices in austere environments such as space (i.e., International Space Station and inflight medical conditions) as a preventive countermeasure to mitigate microbial risks during long space flight missions [1].

A long fiber reinforced glass mat thermoplastic (47 vol.% glass fiber with PA 6, Tepex Flowcore) was selected for the manufacture of demonstrator automobile parts through compression molding. Thermal modeling to predict charge temperature within the production cycle is essential for determining process windows and hence, optimizing process steps. The key inputs for thermal modeling include charge surface heat transfer parameters during each step. In this study, these heat transfer parameters were characterized and validated. The sample core temperature was recorded during each process step, then heat transfer parameters were estimated by fitting experimental data to a one-dimensional thermal model. The estimated parameters were validated by applying them in the modeling of additional samples. Overall, the model predictions show good agreement with experimental results. This suggests that heat transfer parameters have been accurately captured. By knowing these parameters, charge ther...

Asphalt self-healing with encapsulated rejuvenators is a new promising approach to extend the service life of asphalt pavements. Although the research performed so far has demonstrated the crack healing mechanism, no formulation/design for the capsule-bituminous mixture system, aiming to optimize its performance properties, has yet been proposed. This study investigates the effect of calciumalginate capsules, containing sunflower oil, on the mechanical properties of bituminous mixtures. Performance-related properties of a continuously-graded bituminous mixture (stiffness, fatigue and rutting) were evaluated for different dosages of capsule incorporation (0.50, 0.75 and 1.00 wt%). The results showed that the stiffness properties of the bituminous mixture are affected by capsules and that this effect evolves with bitumen ageing. The stiffness modulus after ageing treatment was close to the bituminous mixture with 0.50 wt% and 0.75 wt% capsules and to the reference material. The fatigue resistance of all bituminous mixtures was similar and the bituminous mixtures with capsules did not show an improvement in fatigue resistance after resting, in comparison with the reference material. However, the results clearly indicated that the rejuvenator was released from the capsules and diffused into the bitumen. The bituminous specimens with capsules showed a strong rutting resistance, and the performance was even improved after the rest period.

There are many different ways to reduce the construction industry's impact on environment. The incorporation of waste in the fabrication of construction materials may be beneficial for both the waste management sector and the construction industry. The aim of this research was to investigate the use of three different waste materials (construction and demolition waste, brick powder and fly ash) as filler in asphalt mixtures. Limestone filler was used as reference material. The materials were characterized in terms of their geometrical, physical and chemical properties, and the interaction with bitumen was assessed with two mastic test methods using four different bitumens. The specific surface of waste materials shows a wide-ranging variation due to material specific shape and texture of particles. However, the Rigden voids and bitumen number tests adequately measure the stiffening effect of these materials. The delta ring and ball test results showed there is a good relation with the filler content when the results are affected by the bitumen type. The f/b ratio for a specific bitumen-filler combination can be determined from the maximum filler-to-bitumen ratio and the recommended stiffening increase. The mastics with these waste materials showed strong resistance to water damage.

The addition of a mineral additive to Portland cement involves an increase of the setting time allotted to the dilution effect (dilution of the most active ingredient) and to the increase in the necessary water to prepare a normal consistency paste. In this study, ordinary cement was substituted by 5, 15 and 25% of limestone powder, 10, 20 and 30% of natural pozzolan and 10, 30 and 50% of slag. The tests of penetration are carried out every 10 min in order to determine initial and final setting time. The mortar is prepared and preserved at curing temperature of 20, 40 and 60°C. The results are analyzed and quantified by using the maturity method where the effect of each addition appears more explicit. The value of the activation energy calculated at the very early age reveals the state of activity of these mineral additives and their temperature sensitivity. For replacement amounts lower than 15%, the activation energy of the three additives increases at the initial setting and beyond this content a clear difference is observed. At the final setting time, the activation energy remains constant for limestone, increases regularly for slag and increases highly for natural pozzolan with replacement amounts above than 20%.

In our daily lives, plastic has always played a significant role. Sugarcane molasses is a byproduct of sugar production, and a potential raw material to develop biodegradable plastic which neither causes deforestation nor affects food supply. To address this issue, molasses-based plastic was cross-linked with a succinic acid cross-linker chemical, and locally available sisal fiber was used as reinforcement to improve the plastic's properties and reduce water absorption. The sisal fiber was manually extracted with a sharp knife and alkaline treated with an 8% NaOH solution before being utilized as a reinforcement. Additionally, acid hydrolysis methods were used to pre-treat crude raw cane molasses. After treating the molasses, the lactic acid was recovered and purified by adding cultured yogurt lactic acid to the treated molasses, and then the lactic acid was converted to PLA utilizing direct solution polymerization and condensation techniques in this experiential work. Using the solvent casting process, four (4) bioplastic film samples were made after each extraction and treatment of raw materials. Using a digital microbalance to establish the initial weight of a dry sample and immersing the film sections in distilled water, the swelling experiment was carried out to identify the best cross-linker concentration, crosslinking duration, and crosslinking temperature. According to the findings, water absorption of non-crosslink plastics decreased from 96% to 70% after adding 5% SFR and from 96% to 45.14% after optimum crosslinking with 10%SuA. Furthermore, the synergistic effect of the two (10% SuA and 5% SFR) further reduced the water absorption of the plastic film from 96% to 41.43% at a cross-linker temperature and time of 110°C and 30 minutes. In addition, the biodegradability of the plastic films was investigated, and the findings confirmed that all of the plastic films were biodegradable after 40 days of burial in natural soil. For plastic samples of (neat PLA, 5% SFR-PLA, 10% SUA-PLA, and 5%SFR/10%SUA-PLA), the degradation in 40 days was 97%, 85.26%, 64.26%, and 71.2%, respectively. As a result, SuA cross-linked plastic films were shown to be more water-resistant and have a slower degradation rate than other plastic films.

The search for more sustainable construction materials, capable of complying with quality standards and current innovation policies, aimed at saving natural resources and reducing global pollution, is one of the greatest present societal challenges. In this study, an innovative recycled aggregate concrete (RAC) is designed and produced based on the use of a coarse recycled aggregate (CRA) crushing concrete with electric arc furnace slags as aggregate. These slags are a by-product of the steelmaking industry and their use, which avoids the use of natural aggregates, is a new trend in concrete and pavement technology. This paper has investigated the effects of incorporating this type of CRA in concrete at several replacement levels (0%, 20%, 50% and 100% by volume), by means of the physical, mechanical and durability characterization of the mixes. The analysis of the results has allowed the benefits and disadvantages of these new CRAs to be established, by comparing them with those of a natural aggregate concrete (NAC) mix (with 0% CRA incorporation) and with the data available in the literature for concrete made with more common CRA based on construction and demolition waste (CDW). Compared to NAC, similar compressive strength and tensile strength values for all replacement ratios have been obtained. The modulus of elasticity, the resistance to chloride penetration and the resistance to carbonation are less affected by these CRA than when CRA from CDW waste is used. Slight increases in bulk density over 7% were observed for total replacement. Overall, functionally good mechanical and durability properties have been obtained.

This white paper introduces a novel Scalable Graphene-Based Smart Solid-State Battery designed to address the limitations of conventional lithium-ion batteries in capacity, charge speed, lifespan, and safety. Leveraging advanced materials such as a high-capacity graphenesilicon-carbon (Si/C) anode, an enhanced nickel-doped zinc oxide-titanium dioxide (Ni-ZnO-2 0 8 2 TiO) cathode, and a solid electrolyte, the battery achieves an energy density of 750 to 900 Wh/ kg, a charge time of 0.8 to 1.6 minutes to 80% capacity, and a lifespan of 9,000 to 18,000 cycles. Integrated smart features, including RFID tags and temperature sensors, enable real-time monitoring and IoT compatibility, while a supercapacitor layer enhances power delivery for high-current applications. The battery's modular design supports both 3D-printed casings and vacuum-sealed pouches, ensuring scalability across various form factors (e.g., cylindrical, prismatic, pouch) for applications in consumer electronics, electric vehicles (EVs), grid energy storage, wearables, and medical devices. This innovation contributes to the academic literature by advancing materials science, energy storage, and smart technology integration, offering a cost-effective, high-performance alternative to existing battery technologies.

In the present investigation a new hybrid composites with epoxy as a resin and reinforcing both bio waste (jute) and industrial waste (fly ash) and study of the effect of the fly ash filler on tensile and flexural properties experimentally. Composites were prepared by using hand lay-up technique. All the laminates were prepared with a total of 4 piles. One group of glass laminate was also fabricated for comparison purpose. Specimen preparation and testing was carried out as per ASTM standards. Due to incorporation of fly ash fillers in to the jute composites there is 10 % of strength

As a result of the fast development of new materials, urged by the demand of more durable and resistant materials, fibre reinforced plastic composites (FRP) were introduced as replacement for the reinforcing steel. Carbon FRP has been used since the seventies in the space industry, where the requirement for lightweight, high-tensile strength, corrosion and high temperature resistance is essential. Recently, in Brazil and many other countries, FRP composites (mainly carbon) have been used in strengthening slabs (of bridges and parking f loors), beams (of

For several years, many studies have focused on the mix-design and characterization of cementitious composites reinforced with plant fibres. It appears that in the fresh state, the morphology and the hydrophilic nature of these fibres significantly affect the rheology of the material. In the hardened state, the mechanical performance of the composites is lower than that of the composites including synthetic fibres. These low mechanical performances are mainly due to the weak fibre/matrix interface. Indeed, the high-water absorption capacity causes swelling/shrinkage of the fibre within the matrix, which subsequently leads to a lack of fibre/matrix bond. This work proposes to study the influence of a coating treatment with linseed oil applied to flax fibres on the properties of cementitious composites. The first part of this study deals with the optimisation of this treatment. The second part focuses on the effect of this treatment on the fresh state properties of the composite. The results showed a strong improvement in the workability of the treated fibre composites. A pronounced effect of the linseed oil treatment on air content was noted for high fibre content.

Given the low mechanical strength, hemp concrete cannot therefore be used as a load bearing material. Hemp concrete principal weakness point is the strength but the lack of information concerning the durability performance of this material can also be an explanation for the professional's reluctance to use bio-based concrete. This study focused on the effects of aggregate treatments, linseed oil and two different binders. The mechanicals performance such as the compressive strength at 7, 14 and 28 days were done. The results shows that with higher density treated samples get a higher strength in compression.. Then hydraulic performance was tested with the capillarity test and highlighted the great decrease of sorption coefficient on treated samples. Finally the durability performance tests included the full water immersion test, and the carbonation test in accelerated chamber. Weathering results are better for treated sample compared to none-treated, which are less absorbent and less destructive for specimens. Treated samples carbonated quicker than no treated ones.

This paper presents basic tribological properties of A356/10SiC/1Gr hybrid composites in conditions with lubrication. Hybrid composite specimen is obtained by compocasting procedure. A356 aluminium alloy is used as a base matrix alloy, reinforced with 10wt% of SiC and 1wt% of graphite. Tribological tests are done on advanced and computer supported tribometer with block-ondisc contact pair. By the experimental plan, test is conducted under three different values of sliding speed, three different values of normal load, different sliding distances, and also different lubricants. SEM and EDS are used for wear analysis. The analysis has shown the presence of MML, which means that there was transfer of material from steel disc to composite block.

A method was developed for the geometrically nonlinear analysis of the static response of thin-walled stiffened composite structures loaded in uniaxial or biaxial compression. The method is applicable to arbitrary prismatic configurations composed of linked plate strips, Results obtained using the method are compared with both experimental and analytical results in the literature. The configurations investigated include several different unstiffened and blade-stiffened panel configurations, featuring both homogeneous, isotropic materials and Abstract ii laminated composite material. Results for the Iocal-postbuckling response of stiffened and unstiff'ened panels agree well with results in the literature for moderate postbuckling load levels. In flat blade-stiffened panels which exhibit significant interaction of the local and Euler buckling modes, the method is successful in predicting the consequent imperfection sensitivity, but the method loses accuracy as imperfection amplitudes are increased.

Before we begin, we need to discuss terminology. We're amazed at the variety of terms in the industry that are used to refer to a UTM. Most common are “tensile tester”, “compression tester” and “bend tester”. Today, a UTM can perform all of these tests and more. A UTM is a great multi-purpose instrument for an R&D lab or QC department. Thus, keeping in view the diversified scope in the engineering field, we have opted to design a Universal Testing Machine and to comply with the reduction of physical effort, the testing mechanism is automated along with the inclusion of all necessary parameters and the movement of the members. The main ideas behind opting this project of designing a UTM is to provide a helping hand to the students and personnel associated with the Mechatronics Engineering field and to provide them the better understanding of the UTM machine of international standard. Secondly, provide Pakistan this machine, manufacturing it locally at a very reasonable cost with ...

Recently, RILEM TC 162-TDF Committee has proposed a specimen configuration, test procedures and flexural tensile strength parameters to characterize the post-cracking behaviour of the steel fibre reinforced concrete (SFRC). The approach proposed by RILEM is still yet under discussion, mainly, the ability of the flexural tensile strength parameters to simulate the post-cracking behaviour of the SFRC on the verifications to the ultimate and serviceability limit states. Taking the recommendations of the RILEM, the influence of the fibre content, the concrete age, and the percentage of cement replaced by fly ash on the bending behaviour of the SFRC was analysed in the present work. The influence of the fibre distribution on the fracture surface of the specimens was also considered. The experimental campaign was carried out with a cost competitive SFRC developed for industrial pavements. Bending tests with concrete specimens reinforced with conventional bars and steel fibres were also performed for developing a reinforcement system adjusted for panels of industrial pavements heavily loaded. The results obtained are presented and analysed.

In Portugal, steel fibres are the most used for concrete reinforcement, and flooring and tunnelling are the main applications of fibre reinforced concrete (FRC). In last years the prefabrication industry is showing more interest in collaborating in FRC research projects. The research carried out in consortium by University of Minho (UM) and two private companies for the development of self-compacting steel fibre reinforced concrete (SCSFRC) is an example of this new strategy. This research has the following main tasks: conceive a rational mix design method; evaluate the most relevant material properties and the structural behaviour of laminar elements; develop numerical tools. This paper intends to show the research strategy adopted in the SCSFRC project, since it is a typical example of the methodology followed by the UM research group, the most active in Portugal, in the FRC domain.

The latest research is about ProsopisJuliflora’s mining and characterization officers. The fibres were cut, chemically treated using sodium and hydrochloric acid (alkali) solutions. Chemically modified and non-modified fibres have been analysed for their thermal, chemical, crystalline, electrical, morphological and tensile characteristics. The findings showed that a cellulose content was increased by 59.8 % with a reduction of amorphous content and humidity by chemical treatment with alkali. However, due to its acid-plus attacks whose values were lower than untreated, the treatment for hydrochloric acid reduced cellulosis material. There were four hundred and seventeen nm of crystalline fibre of alkaline therapy, less than one 68.01 nm. Thus the ProsopisJuliflora can be suggested for lightweight polymer applications as a possible reinforcement.

The curved steel-concrete-steel (SCS) sandwich structure has been developed as the iceresistant wall for Arctic oil and gas drilling platform. This developed curved SCS sandwich structure adopts ultra-lightweight cement composite and overlapped headed shear studs as the core material and bonding measures at the steel-concrete interface, respectively. This paper develops a three-dimensional finite element (FE) model by general commercial FE program ABAQUS to simulate the ultimate strength behaviour of the curved SCS sandwich beam. The developed FE model considers the geometric and material nonlin-earities of the concrete, steel plates and connectors. The reasonable agreement between FE analysis and the quasi-static tests on nine SCS sandwich beams confirms the accuracy of the FEM in predicting the ultimate shear resistance and cracks in the concrete core of the curved SCS sandwich beam. Based on this validated FE model, a subsequence parametric study comprising 54 cases investigates the influences of the curvature, thickness of the steel face plate and core material, and horizontal movements of the supports on the shear resistance of the curved SCS sandwich beams. Finally, the paper validates accuracy of an analytical model on the shear resistance of the curved SCS sandwich beam via a comparison against a total of 41 results (32 FEA and 9 tests).

The chloride content at which reinforcement corrosion occurs (Ccrit) is an important parameter for the determination of the service life of a concrete structure. Many studies have been conducted on Portland cement concrete but few data are available concerning slag concrete. In this study, a method for determining the Ccrit value is proposed. It uses capillary suction and a diffusion phase with steel-potential monitoring during the progressive contamination of the concrete by chloride. The same experimental process, capillary suction then diffusion, was performed simultaneously with tap water and chloride solution to verify the specific behaviour of specimens due to the presence of chloride. During the phase of diffusion and potential monitoring, samples were kept immersed in saturated conditions. The criterion for detecting corrosion initiation was a variation of about -250 mV (Ghods et al., Corrosion Science 52:1649-1659, 2010), which corresponds to the difference usually noted between steel in the passive and active state. Two concrete compositions were investigated: one with only Portland cement as the binder and one incorporating slag with a substitution level of 60 %. As expected, in the Portland cement concrete, a drop in potential occurred when corrosion started. For slag concrete, no potential drop was recorded because the initial potential of the steel before the introduction of chlorides was lower. The method for determining Ccrit, based on the fall in potential recorded when corrosion started, would not be suitable to compare the different compositions of binder in saturated conditions. The presence of sulphides in the pore water solution of the slag concrete is a possible explanation of this result. Tests in a solution with added sulphides tended to confirm this hypothesis.

Soils with a significant proportion of clay or silt tend to have poor geotechnical characteristics (such as volumetric change and low strength) when exposed to varying moisture contents. The chemical stabilizers currently used are costly and have negative effects on the environment. Arkansas, in the United States, is the leading producer of rice in the country. During rice production, ~20% of the harvested grain consists of rice husk (RH). The rice milling process produces ash with a considerable amount of silicate. Research is being conducted to address the environmental concerns associated with its disposal in Arkansas, as there is growing interest in using rice husk ash (RHA) as a stabilizing additive for problematic soils. For RHA to be effective, an activator such as lime may be needed. The present study focuses on investigating the effectiveness of RHA in stabilizing substandard soils, as no prior study has used RHA as a stabilizing agent in the United States. Additionally, the research aims to determine the optimal proportions of RHA, hydrated lime (HL), or a combination of both. The study employs varying percentages of RHA (3%, 6%, and 9%) and HL (1%, 3%, and 5%) in a unary system. In the binary system, 3%, 4%, and 5% of RHA are combined with 1% HL. The study includes a range of routine tests, such as assessments of Atterberg limits, modified proctor compaction, pH levels, California bearing ratio (CBR), unconfined compressive strength (UCS), and free swell (FS). Furthermore, results from scanning electron microscopy (SEM) coupled with X-ray diffractometer analyses demonstrated significant improvements in UCS and CBR values for the treated soils, indicating enhanced strength and stability. Moreover, the FS test reveals a reduction in swelling characteristics for the stabilized soils. It was found the optimal dosages of RHA and HL were 6% and 3%, respectively. Notably, when RHA and HL were combined, a blend of these two stabilizing agents exhibited the most promising results in terms of improving the swelling. The optimum percentage of the combined stabilizing agents was 4% RHA + 1% HL. The findings of this proof-of-concept research hold substantial potential for the construction industry in Arkansas, offering cost-effective alternatives to conventional soil stabilization methods while promoting the sustainable and environmentally conscious use of RHA.

In this paper, a new application of resonant acoustic spectroscopy (RAS) is examined for constructing asphalt concrete mastercurves from seismic testing. The frequency-dependent material properties can be characterized from multiple modes of vibration through the use of RAS. Beam-shaped asphalt specimens are tested at multiple temperatures to determine the resonance frequencies of the specimens. The resonance frequencies are estimated by applying a small load impulse and measuring the resulting acceleration through the specimens. Using RAS, the material properties of the specimens are determined numerically using the measured resonance frequencies. The results presented show that the frequencydependent dynamic modulus of the asphalt concrete specimens can be characterized using several modes of vibration at each testing temperature.

This project involves an evaluation of behaviour of circular GFRP tubes under axial compression. Circular tube columns having different length and cross sections resulting in the range of combinations of global and sectional slenderness, were tested under axial load. From this study, the compressive strength, ultimate load and failure modes were determined. After experimental investigation on evaluation of behavior of GFRP tubes, numerical investigation process is started, using ANSYS. Finite element models of the circular tubes will be generated and analyzed using SHELL elements. In this process orthotropic properties has been defined to align the material direction of the composite lay-up and stacking sequence. The experimental results were compared with the analytical results. It includes the parametric study of L/D and D/t ratio of various dimensions and orientation in finite element model. It gives the best orientation angle for the compressive behavior of GFRP tubes

In the recent years, geopolymer concrete is green technology of construction materials. Geopolymer concrete as a based battery composites with an innovative construction smart material for energy storage applications. The characterization of geopolymer-based battery by back carbon mixing with different of amount compositions. After mixing, the battery samples were carried out with all properties. The performance of the battery is based on the structural, morphological, electrical and electrochemical properties of the electrolytes. The results show that the properties of the battery are closely related to the percentage of chemicals composition.

Ich bin all jenen zu Dank verpflichtet, die diese Arbeit möglich gemacht haben und mit ihrer unbezahlten Mühe in Form von Abschlussarbeiten und Projektarbeiten Vorarbeit geleistet haben. Zwar ist umfangreicher Aufwand oft in wenige Sätze und einzelne Bilder komprimiert (entsprechende Stellen sind gekennzeichnet), um dann allerdings darauf aufzubauen und weiter in die Tiefe zu gehen. Die Kürze verbirgt, wie wichtig diese Grundlagen sind. Zu nennen sind besonders Timon Eckstein, Bernd Eisenbarth und Gent Cerimi. Ich danke meinen Freund*innen, die meine Stimmung aufgebessert haben und die Rechtschreibung und Form der Arbeit verbessert haben. Danke an die Mitarbeiter im Robotiklabor, für Unterstützung und Ablenkung.

We present IntU package for Mathematica computer algebra system. The presented package performs a symbolic integration of polynomial functions over the unitary group with respect to unique normalized Haar measure. We describe a number of special cases which can be used to optimize the calculation speed for some classes of integrals. We also provide some examples of usage of the presented package.

Resumo: Compósitos termoplásticos a partir de poliamidas 6 e 6,6 e tecido de fibras de carbono com 40, 50 e 60 % em volume de reforço foram processados via moldagem por compressão a quente e caracterizados por ensaios mecânicos destrutivos (cisalhamento interlaminar em três pontos (short-beam), cisalhamento interlaminar por compressão (CST) e ensaios de mecânica da fratura) e por inspeção não-destrutiva (ultrasom e microscopias óptica e eletrônica de varredura). Os resultados obtidos mostraram que os compósitos termoplásticos processados apresentaram uma distribuição homogênea do polímero no reforço. Entretanto, nos compósitos com maior quantidade de poliamida (40 % de reforço) foram observadas regiões ricas em matriz entre as camadas de tecido. Os ensaios de mecânica da fratura (DCB e ENF) e de cisalhamento interlaminar em três pontos não apresentaram falha interlaminar, não sendo observada a propagação de trincas de forma homogênea e retilínea no interior do material. Em função destes resultados foi utilizado o ensaio de cisalhamento por compressão, desenvolvido no Institute of Polymer Research Dresden da Alemanha, que permitiu uma caracterização mais precisa dos compósitos termoplásticos estudados. Foi observado também, a partir dos ensaios de CST, que os compósitos obtidos da poliamida 6,6 apresentaram um aumento no valor do cisalhamento interlaminar de até 20 % com o aumento do volume de fibras.

The present article deals with the buckling response of functionally graded multilayer graphene platelet-reinforced composite (FG-GPL RC) rectangular plates with circular/elliptical cutouts resting on a Winkler-type elastic foundation under uniaxial and biaxial normal and shear loads. Rule of mixtures and the Halpin-Tsai approach are applied to obtain the effective Poisson's ratio, mass density, and elastic modulus of the reinforced composite. The governing equations are developed by applying the third-order shear deformation plate theory. Then, the finite element procedure is used to solve the problem. Four different types of graphene platelet distributions, namely, UD, FG-X, FG-V, and FG-O, are considered. A broad range of factors such as plate aspect ratio, plate slenderness ratio, applying uniaxial and biaxial normal and shear loads to the plate, several Winkler elastic foundation stiffness parameters, different displacement boundary conditions, the effect of size of the circular cutout and orientation of the elliptical cutout, and the influence of GPL weight fraction are discussed in several tabular and graphical data in detail.

This paper investigates the feasibility of using the small-dimension break-off test for evaluation of the bond quality at the interface between steel bar and concrete. Experimental studies were performed on bar-type concrete specimens and reinforced concrete beams. Twelve bar-type concrete specimens containing plain and deformed steel bars with different diameters were used to develop the relationship between the break-off moment and the adhesive strength at the steel bar/concrete interface. Subsequently, three reinforced concrete beams containing normal reinforcing bars, epoxy-coated reinforcing bars, and bars smeared with oil to simulate various adhesive conditions at the bar/concrete interface were used to study how the break-off moment and the bond strength were affected by the different adhesive conditions. In addition, two beam specimens containing normal reinforcing bars were vibrated severely on a self-made shaking table shortly after initial setting of concrete to simulate the bond damage in fresh reinforced concrete beams due to unexpected vibration or impact. Experimental results show that the effective break-off moment has a good correlation with the adhesive strength at the interface between steel bar and concrete. The break-off moment increases with an increase in bond strength. It is demonstrated that the small-dimension break-off test is capable of evaluating damage at the steel bar/concrete interface.