Types Of Materials Research Articles

A Preliminary Experimental Study on Biodegradation of 3D-Printed Samples from Biomass–Fungi Composite Materials

Products made from petroleum-derived plastic materials are linked to many environmental problems, such as greenhouse gas emissions and plastic pollution. It is desirable to manufacture products from environmentally friendly materials instead of petroleum-based plastic materials. Products made from biomass–fungi composite materials are biodegradable and can be utilized for packaging, construction, and furniture. In biomass–fungi composite materials, biomass particles (derived from agricultural wastes) serve as the substrate, and the fungal hyphae network binds the biomass particles together. There are many reported studies on the 3D printing of biomass–fungi composite materials. However, there are no reported studies on the biodegradation of 3D-printed samples from biomass–fungi composite materials. In this study, two types of biomass materials were used to prepare printable mixture hemp hurd and beechwood sawdust. The fungi strain used was Trametes versicolor. Extrusion based 3D printing was used to print samples. 3D-printed samples were left for five days to allow fungi to grow. The samples were then dried in an oven for 4 h at 120 °C to kill all the fungi in the samples. The samples were buried in the soil using a mesh bag and kept in an environmental chamber at 25 °C with a relative humidity of 48%. The weight of these samples was measured every week over a period of three months. During the testing period, the hemp hurd test samples lost about 33% of their original weight, whereas the beechwood sawdust samples lost about 30% of their original weight. The SEM (scanning electron microscope) micrographs showed the presence of zygospores in the test samples, providing evidence of biodegradation of the test samples in the soils. Additionally, the difference in peak intensity between the control samples and test samples (for both hemp hurd and beechwood sawdust) showed additional evidence of biodegradation of the test samples in the soils.

Recent Progress on Perovskite Materials for VOC Gas Sensing.

Volatile organic compound (VOC) gases are highly hazardous to human health, and their presence in the human breath plays an indispensable role for the early diagnosis of various diseases (cancer, renal failure, etc.). In recent times, perovskite materials have shown notable performance in the detection of VOC gases with high accuracy, fast response, recovery time, selectivity, and sensitivity, owing to their unique crystallographic structures and excellent optoelectronic properties. In this Review, we look at recent reports on perovskite-based sensors and their sensing performance toward VOC gases. Here, we focus on the sensing mechanisms of two types of perovskite materials, metal halide and metal oxide perovskites, and explain the differences in their crystal structures. We also discuss the common preparation methods used by researchers for the synthesis of these perovskite materials. Further, we elucidate various important factors influencing the sensing performance of perovskite-based sensors, such as doping, defects, morphology, temperature, humidity, and light. We conclude with the future prospects and challenges related to these perovskite-based sensors toward the detection of VOC gases.

Performance of concrete beams strengthened with FRP rods: A review

Ductility is a critical property in structural engineering, ensuring that beams can undergo significant deformation before failure, thereby giving plenty of notice before disastrous collapse. This study investigates the ductility properties of constructions that have been reinforced using FRP rods, which are increasingly popular due to their corrosion resistance, superior strength with low mass, and durability. Traditional steel reinforcement has well-documented ductility properties, but FRP bars, due to their brittle nature, pose challenges in achieving the desired ductility levels in structural applications. This research evaluates various factors influencing FRP-reinforced beams' ductility, including the type of FRP material, the hybridization of FRP with other reinforcing materials, and the effect of utilizing fibres in the mixtures to enhance the mechanical characterstics of concrete. Studies have indicated that the ductility of beams can be enhanced using hybrid rebar systems, which integrate steel and fibre reinforced polymer. However, complex and expensive production methods limit their practical application. Using steel bars with FRP bars can significantly incresese seriviceability requiremts such as crack width and deflection, but they also lower corrosion resistance, especially in aggressive environments. The beams' overall ductile behavior is primarily determined by the concrete's characteristics. Fibres greatly increase the mechanical characteristics, toughness, and ductility of the concrete mix, strengthening the bond between bars and the concrete and improving the overall performance of the beam.

Raw Materials in the Paste of Ceramics of the Kulaika Culture Surgut Variant (Based on Samples from Barsova Gora)

A multidisciplinary analysis of ceramics from six sites of the Surgut variant of the Kulaika culture at Barsova Gora was made. Technology was assessed using traceological, petrographic, and X-ray phase analyses. At all the sites, the potters used ferruginous clays tempered with grus, grog, sand, and organic material. Fragments in the clay were either rounded, as in sand, or coarse, as in grus. The sand was mainly represented by feldspar and quartz, suggesting that this type of raw material was extracted from nearby non-metallic mineral deposits. The grus consisted of fragments of basaltoids, amphiboles, and pyroxenes, evidencing that it came from igneous common rocks associated with the Surgut volcanic fi eld and spread over a large area. Rocks were probably mined near settlements, perhaps on the floodplain of the Ob. Grog in all the samples was similar to the basic clay in terms of its composition. Three groups of sites were identified, differing in the composition of the clay of which the ceramics were made. This may indicate the presence of several groups within the Iron Age Kulaika population, utilizing various sources of clay.

Hard carbon anode materials for hybrid sodium-ion/metal batteries with high energy density

Interest in sodium-ion batteries (SIBs) as a lower-cost alternative to lithium-ion batteries (LIBs) is growing in both scientific and industrial fields. However, uneven premature sodium deposition and dendrite formation during cycling pose a serious safety threat, significantly limiting the application of SIBs. Achieving reversible and dendrite-free sodium metal deposition and dissolution on the anode surface is key to developing anode-less sodium batteries, the next generation of SIBs with energy densities comparable to those of LIBs. In anode-less systems, sodium ions not only intercalate into the anode's structure but also deposit on its surface, thereby multiplying the specific capacity. Here, we evaluate state-of-the-art hard carbon (HC) used in traditional SIBs as a potential anode material for anode-less sodium batteries. We present comprehensive research on sodium-ion/metal storage, depending on the type of carbon anode material, particle size and morphology of hard carbons, and the electrolyte and additives used. Half-cells with microspherical HC and a fluoroethylene carbonate-based electrolyte operated for over 3000 h, yielding an average discharge capacity of 550 mAh g−1, nearly twice that of HC in classic SIBs. Anode-less Na3V2(PO4)3||HC full cells demonstrated up to 25 % higher energy density and working potential compared to traditional full cells.

Comparison of Lab vs. Backcalculated Moduli of Virgin Aggregate and Recycled Aggregate Base Layers

The resilient modulus (MR) and the backcalculated modulus from the FWD testing (EFWD) of the unbound layers are critical inputs in the analysis/design of pavements. Several studies have tried to develop a conversion factor between these two parameters, while the nonlinear stress dependency of unbound materials and the pavement strain response are mostly missing from the literature. This study aims to compare the laboratory-measured MR of recycled aggregate base (RAB) materials and a virgin aggregate base using field-based EFWD and tries to establish pavement’s responses to loading using vertical strains from both the MR and EFWD values of the respective materials as comparability parameters between the two. For this purpose, a control virgin aggregate (VA, limestone) and three types of RAB materials were selected to construct four test sections. The test sections were modeled in layered elastic- and finite-element-based pavement response models to calculate the vertical strains at the mid-depth of the base and top of the subgrade layers. A comparison of the lab-calculated vertical strains using MR with actual vertical strains in the field from EFWD showed that there was no relationship between the two stiffness parameters in all tested RABs. The vertical strains, based on the lab MR, undermined the stiffness of the recycled aggregates in the field. In contrast, the values of EFWD based on the vertical strains remained close to the MR strains of limestone (VA) throughout the testing period, establishing an EFWD vs. MR relationship (MR = 0.87 EFWD). The results also show that fine RCA was a better-performing material over three years. This research not only explores how the hydration process in RABs limits the development of MR-EFWD correlations but also underscores the need to consider real-world conditions when assessing their performance.

Computer Design of the Regulating Working Element of the Channel Cleaning Equipment

Cleaning devices of channel systems used for irrigation of agricultural plants and mechatronic parts regulating their operations were analyzed, the issues of automation of construction design, measurement and management in this field were examined and the purpose of the work was determined. As the goal of the work, the issue of automation of the construction design, technological measurement and management process of the working body for efficient cleaning of small and medium-sized concrete-covered channels, bathtubs from sludge and weeds was set. A complex scheme of information, algorithmic and software support for the automation of the design, technological measurement and control of the mechatronic parts of the working body used for cleaning the channel and bathtub was proposed, and the issues of logical modeling and simulation of the drawing of 2- and 3-dimensional images of the working body were solved. Algorithms were developed using the production modeling method to automate the process of technological measurement, implementation and management, which accurately regulates the operations of the working body of the mechanical device of complex construction. In Solid Edge 2D, 3D software environments, the determination of the geometric shapes of the individual mechanical parts of the channel cleaning unit with a milling cutter, their sizes and types of materials is ensured, and the algorithm was developed using the logical modeling method. For the automation of the structural design process, the information security of the mechanical parts of the application object and the elements of the new design milling cutter device was created for the management of the database of drawings.

Study on Flexural Performance of Reinforced Concrete Beams Strengthened with FRP Grid–PCM Composite Reinforcement

To study the flexural performance of fiber-reinforced polymer (FRP) grid–polymer cement mortar (PCM)-composite-strengthened RC beams, the finite element numerical simulation of FRP grid–PCM composite RC beams is carried out using ABAQUS to analyze the effects of the amount of FRP grid reinforcement, the type of FRP grid material, and the geometry of FRP grid on the flexural performance of reinforced concrete beams and to establish the flexural capacity calculation formula of FRP grid–PCM-reinforced RC beams in case of debonding failure, based on analysis of the influencing factors. The results show that increasing the reinforcement of the FRP grid and increasing the stiffness of the FRP grid can improve the flexural bearing capacity of RC beams, and the change of FRP grid geometry has little effect on the flexural bearing capacity of RC beams. The established formula for calculating the flexural bearing capacity of FRP grid-reinforced concrete beams can better predict the flexural capacity of reinforced concrete beams under peeling failure.

Using Post‐Treatment Additives for Crystal Modulation and Interface Passivation Enables the Fabrication of Efficient and Stable Perovskite Solar Cells in Air

AbstractHigh‐performance perovskite solar cells (PSCs) fabricated in ambient air are considered inevitable for low‐cost commercial manufacturing. However, passivating perovskite film defects and controlling the crystallization process are critical for achieving high performance in PSCs. This study proposes using the novel 2D material MBene in green antisolvent to simultaneously modulate the crystallization and passivation defects of perovskites. MBene facilitates the passivation of uncoordinated Pb2+ ions, thereby enhancing the formation energy of vacancies within the perovskite film and adjusting the energy level structure. Moreover, MBene increases nucleation sites for perovskite, significantly extending crystal growth and improving film crystallinity, thereby reducing non‐radiative recombination. Consequently, champion devices treated with MBene achieve a power conversion efficiency (PCE) of 24.22% when fabricated in air, and exhibit superior humidity and long‐term stability. Furthermore, PSCs with added MBene exhibit significant long‐term stability under various environmental conditions, including humidity and heat. The study results lay a foundation for the development of MBene materials in photovoltaics, revealing their mechanism as a new type of 2D material in perovskites, and providing new insights for industrially producing efficient and stable solar cells.

Enhanced cyclability and energy density of mid-nickel layered oxide cathode material LiNi0.55Mn0.25Co0.20O2 by niobium doping via solvothermal method

Ni-based layered oxide materials are among the most promising cathode materials for the next generation of lithium-ion batteries due to their higher energy capacity. However, capacity decay occurs due to degradation mechanisms that reduce the electrochemical performance of this type of material. This work aims to synthesize Nb-doped LiNi0.55Mn0.25Co0.20O2 (Nb-NCM) materials via the solvothermal method to enhance the cyclability and energy density of the layered oxide cathode. The effects of Nb doping on the microstructure and the electrochemical performance of the cathodes are investigated. The introduction of the contents of Nb expands the structural lattice parameters and decreases the Li+/Ni2+ cation mixing degree of the NCM cathode. Furthermore, the Nb doping enhances the electrochemical activity of LiNi0.55Mn0.25Co0.20O2, increasing its initial discharge capacity to 169.61 mAhg−1 when 1% of Nb was used as a dopant (1%Nb-NCM) in contrast to the capacity of 149.45 mAhg−1 presented by the pristine material. The modified 1.0%Nb-NCM material also exhibits remarkable cycling performance with a capacity retention of 92.7% after 100 cycles at the rate of 1 C (2.8–4.3 V). This work suggests a rational strategy for high-performance cathode for lithium-ion batteries, proposing the extension of Nb doping to enhance Ni-mid material's cyclability.

Analysis of Thermoelectric Properties of Hot-deformed Bismuth Telluride Sintered Materials

Bismuth telluride (Bi2Te3)-based alloys are widely used for thermoelectric cooling and power generation at low temperatures, and they are the only commercially available materials for thermoelectric applications below 500 K. The rhombohedral unit cell with a large c/a lattice constant ratio consisting of - Te-Bi-Te-Bi-Te- stacked layers inevitably brings about a large anisotropy in transport properties, which is why texturing is very important in polycrystalline Bi2Te3</sub alloys for maximum performance. In this report, p and n-type polycrystalline Bi2Te3</sub alloys were synthesized and hot-deformed to investigate the effects of texturing on thermoelectric properties. Hot deformation (HD) induces the strong alignment of (001) orientations along the compression direction, and a remarkable increase in the orientation factor F of (001) orientations is observed after HD in both p and n-type materials. All of the hot-deformed polycrystalline samples showed increased electrical conductivity (σ), power factor (PF), and thermal conductivity (k) in the in-plane (IP) direction, and vice versa in the out-of-plane (OOP) direction, which makes the IP direction of the hot-deformed bodies more favorable for module fabrication in terms of power factor, for both p and n-type Bi2Te3</sub-based alloys. However, due to the different degree of anisotropy of k and σ, the figures of merit (zT) were maximized in the OOP direction in the p-type materials after HD, whereas the zTs of the n-type materials were higher in the IP direction. This occurs because the anisotropy factor of electron conduction is higher than that of hole conduction, which more than offsets the advantage of the smaller k in the c-direction of n-type Bi2Te3</sub. The maximum zT of 1.33 (OOP) and 0.90 (IP) were obtained after HD from the p and n-type Bi2Te3 alloys, respectively, which were 9.3% and 18.4% higher than those of as-sintered materials.

Internal Quality Controls in the Medical Laboratory: A Narrative Review of the Basic Principles of an Appropriate Quality Control Plan

To ensure the quality of their analyses, medical laboratories carry out internal quality control (IQC) on a daily basis. IQC involves control samples with known target values for all parameters used by a laboratory in clinical practice. The use of IQC enables the laboratory to monitor the accuracy and precision of laboratory results. The use of appropriate IQC strategies has been accepted in medical laboratories for decades, and IQC has been included in international recommendations and guidelines. The term “IQC strategy” (also termed a quality control plan) refers to the types of IQC materials to be measured, the frequency of IQC events, the number of concentration levels in each IQC event, and the IQC rules to be used. A scientifically sound IQC strategy must follow two principles, namely, (1) statistical follow-up on the IQC results generated in the laboratory by means of Levey–Jennings control charts and Westgard rules (i.e., quality control by means of statistical procedures) and (2) the determination of limits on the basis of medical considerations and the definition of analytical goals (quality control on the basis of medical relevance). In this narrative review, we describe the fundamental principles of an adequate IQC strategy for laboratorians and nonlaboratorians.

Multi-scale topology optimization of periodic structures with orthotropic multiple materials using the element-free Galerkin method

ABSTRACT A multi-scale topology optimization model is proposed for orthotropic multi-material periodic structures using the element-free Galerkin method. The macro multi-material distribution is optimized with the alternating active-phase algorithm, and the effective elastic tensor of multi-type microstructures is determined by energy-based homogenization. The feasibility of the model is verified and the effects of the quantities of material types and design subdomains, the Poisson's ratio factor and the multi-material off-angle on topological configuration and compliance are studied. The results indicate that the quantity of material types affects the mechanical properties of the periodic structure, and different microstructure configurations can be obtained under different numbers of design subdomains. The increase in the Poisson's ratio factor and decrease in the off-angle can enhance the effective elastic properties of the microstructure and reduce the compliance. Reasonable values of the Poisson's ratio factor and multi-material off-angle are suggested to be 2–4 and 0–45°.

Comparative analysis of the heavy-weight floor impact noises using different types of EVA resilient materials

The present study aims to improve the floor impact noises using various shapes of EVA resilient materials in composite floor structures. In order to this, three different types of EVA resilient materials were used including flat plate, deck plate type and cavity type of EVA boards. All the composite structure consisted of PP panel, PET and EVA resilient materials with a total depth from 30mm to 40mm. Total of 9 specimens were made for floor impact sound measurements. All the floor impact sound measurements were done at the recognized testing authority using bang machine. The values of L'I,Fmax,AW were deduced from every measurements. As a result, among the various types EVA resilient materials, most high performances were drawn when cavity type of EVA resilient material was used. It was shown that the average L'I,Fmax,AW value of cavity type was 46dB while 47dB for deck plate type, 48dB for flat plate were measured in average. It can be recognized that the good performance of cavity type EVA materials is caused by the both air layer gap beneath EVA board and air cavity inside the EVA board as well as the low dynamic elastic modulus of EVA.

Poland in Blue: The Phenomenon of the Denim Clothing Industry in Polish Society During the Socialistic Period

In the People’s Republic of Poland 1 , blue jeans were much more than just an element of clothing. They have become a symbol of freedom, a generational rebellion, and an aspiration for the world on the other side of the Iron Curtain. Aid parcels sent by relatives, mainly from the USA and also from Great Britain, Canada, and Australia played a significant role in getting to know denim clothing in socialist Poland. In the second half of the 1960s, the domestic production of substitute denim-like materials 2 , including denim-like trousers, was started. They were a response to the demand, in particular, of groups of young people for products made of this type of material. The new improvements and material inventions were supervised by the association of clothing industries and research laboratories, which played an essential role in the creation of materials for domestic production (Kortan 1981). A group of active Polish textile and fashion designers contributed to promote comfortable denim clothing from the West. This article presents the role of the denim clothing industry in Poland during the socialist period (1952–1989), considering the cultural context and the impact of this clothing on discovering alternative forms, replacing the originals from capitalist countries. It should be noted that in the People’s Republic of Poland, new types of textile materials were developed and improved so that they corresponded, at least in part, to materials from the West and filled in product gaps. To this end, proprietary commercial versions of fabrics used to produce garments, including the jeans discussed in this publication, were made of a textile known as in Polish word “Teksas” a denim substitute. Researching archival materials and showing achievements in the field of textiles and fashion fills the gap in research on cultural significance of fashion, textile materials and the production of denim and clothing from domestic fabrics of the socialist era.

A novel conjugated microporous polymer nano hollow sphere containing N, P and Si flame retardant elements with both thermal insulation and flame retardant properties

It is particularly important to develop new materials with both thermal insulation and flame retardant properties for addressing the severe issues caused by fire accidents. Herein, a kind of conjugated microporous polymer nanospheres with hollow structure (HCMPNS) was synthesized by Sonogashira-Hagihara cross-coupling reaction using SiO2 nanospheres as hard template and 1,3,5-triacetylenebenzene, as alkynyl monomer. Then, HCMPNS was chemically graft-modified with azidotrimethylsilane (TMSA) by "click" chemistry (HCMPNS-FRSi), and the HCMPNS-FRSi obtained from the reaction was introduced into flammable epoxy resin (EP) to obtain EP based composites, i.e. EP-Ⅰ and EP-Ⅱ. The thermal conductivities were found to be 0.0341 W m−1 K−1 and 0.0268 W m−1 K−1 for EP-Ⅰ and EP-Ⅱ, respectively, showing excellent thermal insulation performance. The total heat release (THR), the total smoke production (TSP) and the peak CO2 produced (CO2P) of EP-Ⅰ were reduced by 18.0 %, 8.0 %, 14.3 % compared with pure EP as measured by cone calorimetry (CC), respectively, indicating a certain extent flame retardant effect. In order to further improve its flame retardant properties, phosphoric acid containing the flame retardant phosphorus element was added to HCMPNS-FRSi (HCMPNS-FRSi-P), followed by the introduction of the resulting HCMPNS-FRSi-P into EP matrix to form EP based composites with Si and P dual incorporation (EP-III and EP-IV), with the thermal conductivities of 0.0470 W m−1 K−1 and 0.0855 W m−1 K−1, respectively. Through the cone calorimetry (CC) of EP-III, EP-IV, total heat release (THR) were reduced by 17.0 %, 23.8 %, total smoke production (TSP) were reduced by 6.2 %, 7.2 %, respectively. The peak heat release rate (HRR) and the peak CO2 produced (CO2P) of EP-Ⅳ were reduced by 16 % and 25 %, respectively, compared with pure EP. It has good thermal insulation and flame retardant effect. Therefore, HCMPNS-FRSi-P, as a new type of flame retardant material, has great potential in the fields of electronics, construction, transportation and so on.

Acoustic properties of Helmholtz resonator filled with granulated polymer waste material

This study investigates the acoustic absorption performance of cavity resonators filled with different types of polymer waste material instead of traditional porous material. The absorption spectrum was determined by impedance tube measurements. The data are compared with the ones obtained for the empty resonator and the resonator filled with polyester fiber board. Granulated polymer-filled cavities hold potential applications in construction, particularly as a sound absorber for building facades or noise barriers. This research contributes to the exploration of new sustainable practices within the construction industry. The presented research was performed in the framework of the EU H2020 - MSCA - DN project ActaReBuild.

Nanomaterials Marvels: Transformative Advancements in Biomedicine, Drug Delivery, and Pharmaceutical Analysis

Nanoparticles are solid colloidal particles ranging in size from 10 to 1000 nm having high surface area-to-volume ratio which allows them for efficient interaction with biological systems. Nanoparticles offer many benefits in comparison to larger particles such as increased surface-to-volume ratio and increased magnetic properties. Nanomaterials hold the potential to revolutionize in critical domains like Biomedicine, Drug Delivery, and Pharmaceutical Analysis. These particles can be functionalized with specific molecules to target diseased cells or tissues, enhancing the efficacy of drugs while minimizing side effects. For instance, gold nanoparticles conjugated with antibodies can be used for targeted cancer therapy, delivering therapeutic agents directly to tumor cells. Similarly drugs encapsulated within nanoparticles can be protected from premature degradation and released in a controlled manner at the target site improving their drug solubility, and enhance cellular uptake, leading to better therapeutic effect in treatment strategies. Polymeric nanoparticles, liposomes, and micelles are some examples of commonly used nanocarriers for drug delivery. Nanomaterials are finding increasing applications in pharmaceutical analysis and can be employed as highly sensitive detection probes for drugs, metabolites, and biomarkers. Additionally, nanomaterials can be used for the separation and purification of bio molecules, facilitating accurate and efficient analysis. This review explores different types of nano materials used exploring their new advances and applications in biomedicine, drug delivery, and pharmaceutical analysis. As research continues to overcome current challenges, nanomaterials unique properties hold immense promise for revolutionizing healthcare and improving patient outcomes.

Study on use of recycled waste materials on the performance of asphalt binder and mixes: A comprehensive review

All aspects of daily living frequently involve the use of plastics. Due to the lack of effective waste treatment methods, massive global environmental problems will be caused by the accumulation of waste plastics. The use of waste materials in road building is of tremendous interest since it has the potential to reduce hazards and pollution while conserving natural resources. High-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), ethyl vinyl acetate (EVA), and polyvinyl chloride are the most appropriate and relevant of waste plastics. There are other types of waste materials used in the asphalt such as reclaimed asphalt pavement (RAP), crumb rubber (CR), steel slag, glass powder etc. These all-waste materials have been briefly discussed. In this review article several concerns have been raised about the physical and chemical qualities, of asphalt pavements that have been mixed with waste materials. Using waste materials in asphalt pavements can raise several concerns regarding the physical and chemical qualities of the resulting mixtures. These concerns typically revolve around factors such as durability, performance, environmental impact, and overall sustainability. This research article provides a thorough analysis of the wet and dry procedures used to mix different types of waste plastics. Overall, including waste plastics into asphalt mix improved rutting, fatigue, and moisture resistance. Additionally, recycling waste plastics in this manner helps in reducing environmental pollution and conserving natural resources. Overall, the inclusion of waste plastics in asphalt mixtures can contribute to the development of more sustainable and durable pavements with improved performance in terms of rutting, fatigue, and moisture resistance. There are still certain issues like compatibility and low temperature performances that need to be addressed. To overcome the aforementioned issues, many strategies are used, including the use of nanomaterials, chemical additives, and polymer additives. Additional research should be conducted to investigate the ageing effect, pavement performance monitoring, polymer stability, and the economic and environmental considerations associated with the usage of plastics in asphalt pavements.

Experimental study on damage of steel fiber reinforced concrete- and wood-filled GFRP tubes under axial compression

In order to reduce the self-weight of concrete structures and improve its corrosion resistance, it is an effective way to fill GFRP tubes with wood columns instead of part of concrete. However, concrete structures are prone to cracks, which will reduce the bearing capacity of the structure and affect the safety and applicability of the structure. Incorporating the steel fibers (SF) in concrete seems to be an excellent solution to limit crack propagation and improve the ductility of concrete structures. Based on the premise, in this paper, a new type of structure composite material of steel fiber reinforced concrete- and wood-filled GFRP tubes was developed. The mechanical properties, damage evolution process and crack fractal characteristics of steel fiber reinforced concrete- and wood-filled GFRP tubes under axial compression with different SF volume fractions (0 %, 1 %, 1.5 % and 2 %) were studied by acoustic emission (AE) technology. The finite element method (FEM) was established to simulate the test work and expand the analysis. The results showed that the bearing capacity and ductility of the specimens increased first and then decrease with the increase of SF content, and the specimens with 1.5 % volume fraction of SF showed the best mechanical properties. According to the characteristics of AE ringing counts, the damage process of the specimen was described by three marker events, which were concrete cracking, wood cracking and GFRP tube fracture. The incorporation of SF increased the intensity of AE signal and the proportion of shear cracks, and reduced the damage scale. The fractal dimension of concrete surface cracks had a good correlation with the degree of local damage and the complexity of crack propagation. The damage evolution model based on AE cumulative events and stress obeyed the two-parameter Weibull distribution. The incorporation of SF reduced the degree of damage, and the parameter m had a negative correlation with brittleness. In addition, the damage process of the specimens revealed by the FEM matched well with the experimental results. Additionally, the incorporation of SF made the stress distribution of each part of the specimen more uniform and avoided the phenomenon of stress concentration.