Fiber Reinforcement

Resumo -A necessidade da caracterização de propriedades mecânicas de materiais com comportamento não linear traz novos desafios à engenharia mecânica, tanto no desenvolvimento de novas técnicas experimentais como na implementação de novos algoritmos numéricos. Nas últimas décadas tem vindo a ser feita uma aposta séria na investigação ligada ao estudo e análise de tecidos biológicos, estes têm um comportamento fortemente não linear e de difícil caracterização. No trabalho aqui apresentado faz-se o estudo do comportamento mecânico de tecidos biológicos hiperelásticos, para isso recorreu-se à utilização de uma técnica experimental de campo denominada Correlação Digital de Imagem, esta técnica é relativamente recente e permite a caracterização do campo de deslocamentos, com elevada resolução e sem contacto. As simulações numéricas aqui implementadas foram realizadas num programa comercial de elementos finitos, Ansys®, recorrendo a dados experimentais de ensaios de tracção de tecidos hiperelásticos da mucosa vaginal humana. Na simulação numérica foram utilizados alguns dos modelos constitutivos mais conhecidos no estudo de materiais hiperelásticos: Mooney-Rivlin, Yeoh e Ogden. Os resultados obtidos demonstraram o potencial destas técnicas para a análise do comportamento mecânico de materiais hiperelásticos, verificando-se, contudo, a necessidade de um maior aprofundamento no estudo e aplicação das mesmas a este tipo de materiais.

Bu çalışmada, pim bağlantılı tabakalı kompozit levhalarda fiber takviye açısının değişiminin hasar yükleri ve hasar tipleri üzerindeki etkileri araştırılmıştır. Analizlerde tek yönlü karbon fiberlerle takviye edilmiş epoksi reçine matriksli tabakalı kompozit levhalar kullanılmıştır. Tabaka dizilimleri [θ 0 ] 4 olmak üzere, θ; fiber takviye açısı 0 0 'den 90 0 'ye kadar 15 0 'lik artımlarla seçilmiştir. Levhaların farklı fiber takviye açılarındaki hasar yükü ve hasar tipleri deneysel ve sayısal olarak bulunmuştur. Sayısal çalışmada Ansys programı kullanılmıştır. Tabakalı kompozit levhaların ilerlemeli hasar analizi için Hashin hasar kriteri kullanan APDL kodları yazılarak malzeme indirgemeleri yapılmıştır. Deneysel çalışmada en büyük hasar yükü 749.917 N ile [15 0 ] 4 tabaka dizilimi için ve en düşük hasar yükü ise 467.483 N ile [60 0 ] 4 tabaka dizilimi için elde edilmiştir. Sayısal ve deneysel çalışma sonuçlarının uyumlu olduğu tespit edilmiştir.

A resposta deformacional do betão estrutural é bastante sensível ao modelo constitutivo adoptado na simulação do comportamento pós-fendilhação deste compósito. No estado fendilhado o betão entre fendas retém ainda tensões de tracção devido fundamentalmente aos mecanismos de engrenagem mecânica associados à rugosidade existente nas faces das fendas e aos fenómenos de interacção que se estabelecem entre as armaduras e o betão envolvente. Assim, um modelo constitutivo realista para o betão armado fendilhado deverá incluir as propriedades de fractura associadas ao betão (resistência à tracção, energia de fractura e distância entre fendas) e as propriedades associadas às armaduras que atravessam a fenda, nomeadamente a percentagem, a aderência e a respectiva orientação. No presente trabalho são apresentados alguns dos mais recentes modelos constitutivos propostos para a caracterização do comportamento do betão armado fendilhado, bem como os refinamentos introduzidos visando a obtenção de uma melhoria no respectivo desempenho. É proposto um modelo que inclui na sua formulação os principais parâmetros que governam o presente fenómeno. Os modelos seleccionados foram adaptados por forma a possibilitar a sua inclusão num modelo computacional baseado na decomposição das deformações (a deformação do betão fendilhado resulta das deformações associadas às fendas e ao betão entre fendas) e dispondo de modelos de fendas distribuídas com multifendas fixas não necessariamente ortogonais e fendas rotativas. O desempenho relativo dos modelos constitutivos apresentados e do modelo proposto é avaliado através da comparação das respostas numéricas e experimentais obtidas para um conjunto de painéis de betão armado.

The Japan-USA collaborative program, JUPITER-II, has made significant progress in a research program titled "The irradiation performance and system integration of advanced blanket" through a six-year plan for 2001-2006. The scientific concept of this program is to study the elemental technology in macroscopic system integration for advanced fusion blankets based on an understanding of the relevant mechanics at the microscopic level. The program has four main research emphases: (1) Flibe molten salt system: Flibe handling, reduction-oxidation control by Be and Flibe tritium chemistry; thermofluid flow simulation experiment and numerical analysis. (2) Vanadium /Li system: MHD ceramics coating of vanadium alloys and compatibility with Li; neutron irradiation experiment in Li capsule and radiation creep. (3) SiC/He system: Fabrication of advanced composites and property evaluation; thermomechanics of SiC system with solid breeding materials; neutron irradiation experiment in He capsule at high temperatures. (4) Blanket system modeling: Design-based integration modeling of Flibe system and V/Li system; multiscale materials system modeling including He effects. This paper describes the perspective of the program including the historical background, the organization and facilities, and the task objectives. Important recent results are reviewed.

Analytical models for predicting the mechanical properties of composite materials are useful when experimental procedures are not feasible. This study presents a review of micromechanical analytical models used to
predict the Young’s modulus of fiber-reinforced composites (FRC). The theoretical models assessed in this work include the series and parallel models, the effective modulus approach, the Halpin-Tsai equations, and the Cox and Nilsen models, due to their relatively simple mathematical descriptions. The study focused on an epoxy matrix reinforced with carbon fiber, E-glass, and Kenaf (a natural fiber), as these fillers are commonly used in various industrial and research applications. The comparison between experimental and predicted values indicates that models such as the Halpin-Tsai and effective modulus approach provide better agreement with the experimental measurements for the targeted composites.

Construction materials made of renewable resources have promising potential given their low cost, availability, and environmental friendliness. Although hemp fibers are the most extensively used fiber in the eco-friendly building sector, their unavailability hinders their application in Iraq. This study aimed to overcome the absence of hemp fiber in Iraq and develop a new sustainable construction material, strawcrete, by using wheat straw and traditional lime as the base binder. A comparable method of developing hempcrete was established. The experimental program adopted novel Mixing Sequence Techniques (MSTs), which depended on changing the sequence of mixed material with fixed proportions. The orientation of the applied load and the specimen's aspect ratio were also studied. The mixing proportion was 4:1:1 (fiber/binder/water) by volume. Results showed that the developed strawcrete had a dry unit weight ranging from 645 kg/m3 to 734 kg/m 3 and a compressive strength ranging from 1.8 MPa to 3.8 MPa. The enhanced physical and strength properties varied with the MST and loading orientation. The properties of the developed hempcrete were compared with those of strawcrete.

The stress-strain behavior at room temperature and at 1100 °C (2000 °F) was measured for two carbon-fiberreinforced silicon carbide (C/SiC) composite materials: a two-dimensional plain-weave quasi-isotropic laminate and a three-dimensional angle-interlock woven composite. Micromechanics-based material models were developed for predicting the response properties of these two materials. The micromechanics-based material models were calibrated by correlating the predicted material property values with the measured values. Four-point beam bending subelement specimens were fabricated with these two fiber architectures, and four-point bending tests were performed at room temperature and at 1100 °C. Displacements and strains were measured at various locations along the beam and recorded as a function of load magnitude. The calibrated material models were used in concert with a nonlinear finite element solution to simulate the structural response of these two materials in the four-point beam bending tests. The structural response predicted by the nonlinear analysis method compares favorably with the measured response for both materials and for both test temperatures. Results show that the material models scale up fairly well from coupon to subcomponent level.

This research aims to assess the feasibility of the mechanical strength and the durability of the concrete containing 50% nickel slag and a combination of 15% and 30% fly ash with a water-cement ratio of 0.25 and 0.45 in a marine environment. Four types of concrete, namely OPC-sand (C) as control concrete, OPC-50GNS (S), 15FA-50GNS (F1), and 30FA-50GNS (F2) as comparison concrete, were tested with a 100×200 mm cylindrical specimen. The results showed an increase in the mechanical strength and potential resistance of the comparison concrete at the age of 28 days. While at the age of 180 days, fluctuating changes were found. The compressive strength of S concrete increased by 36.9 and 9.3% respectively, F1 concrete by 37.7% and 1.7%, F2 by 33.7% and 5.9% at ratio 0.45 and 0.25. Likewise, the value of the split tensile strength and modulus of elasticity of concrete. This result was followed by reduced porosity, sorptivity, and chloride penetration resistance as an indication of better concrete durability. Fly ash appears to have a greater positive impact on potential durability than mechanical strength at a water cement ratio of 0.25 versus 0.45. Although the chloride penetration resistance is decent, the compressive strength of concrete with a water-cement ratio of 0.45 does not qualify for application in the marine environment. In contrast, concrete with a water-cement ratio of 0.25 containing 50% nickel slag and the addition of class C fly ash up to 30% was declared suitable for application to concrete in the marine environment zone C2 according to ACI 318-19.

It is well known that unreinforced masonry behaves as a quasi-brittle material when subjected to seismic loading. The construction in unreinforced masonry is usually not allowed in regions with moderate to high seismic hazard. The alternative to unreinforced masonry and even to reinforced concrete and steel construction is reinforced masonry, which appears to perform adequately under seismic loading. This work deals with the challenging issue of contributing to the definition of a fast and simples construction system using reinforced masonry, by replacing the grout by a general purpose bed mortar, capable of being used also to fill vertical cells with vertical reinforcement. The major difficulty is to find a mortar that is also suitable to fill vertical hollow cells of concrete units. This work presents preliminary results from the study of different mortars, corresponding to different compositions, in order to find appropriate workability and sufficient fluidity. The analysis is based on a comparative study including the characterization of the fresh mortar properties, such as workability, and the hardened properties, such as modulus of elasticity, flexural strength and compressive strength. The assessment of the mortar adequacy to fill the hollow cells is also analyzed by the execution of masonry prisms, followed by a qualitative analysis of the fill.

Abrasion by glass fibers during injection molding of fiber reinforced plastics raises new challenges to the wear performance of the molds. In the last few decades, a large number of PVD and CVD coatings have been developed with the aim of minimizing abrasion problems. In this work, two different coatings were tested in order to increase the wear resistance of the surface of a mold used for glass fiber reinforced plastics: TiAlSiN and CrN/CrCN/DLC. TiAlSiN was deposited as a graded monolayer coating while CrN/CrCN/DLC was a nanostructured coating consisting of three distinct layers. Both coatings were produced by PVD unbalanced magnetron sputtering and were characterized using scanning electron microscopy (SEM) provided with energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), micro hardness (MH) and scratch test analysis. Coating morphology, thickness, roughness, chemical composition and structure, hardness and adhesion to the substrate were investigated. Wear resistance was characterized through industrial tests with coated samples and an uncoated reference sample inserted in a feed channel of a plastic injection mold working with 30 wt.% glass fiber reinforced polypropylene. Results after 45,000 injection cycles indicate that the wear resistance of the mold was increased by a factor of 25 and 58, by the TiAlSiN and CrN/CrCN/DLC coatings, respectively, over the uncoated mold steel.

The term Stress Intensity Factor – SIF, is one of the fracture parameters which describes stress intensity around crack tip, represented by variable K. Depends on its critical value Kc, structural failure capacity might be analyzed based on the view of point of fracture mechanics. This study focuses on how reinforcement influences the rate of crack propagation. Wedge forces developed by cohesiveness between re-bar and concrete is the main concern in transforming brittle failure to plastic failure by means reducing the value of K. Specimen with three point mode I fracture reinforced high strength concrete beam was used in analytical processing. It is a mode I fracture beam of (150x300) mm with 100 mm initial crack. This specimen is reinforced by 4#12mm steel bar. Under wedge forces due to a center bending load, led a value of K equal to 482.70 Nmm for beam without reinforcement, whereas 441.613 Nmm for beam with reinforcement.Superposition of these both actions prevails the net of st...

Abstract-This article summarizes the current level and trends in the emerging Morphing Air Vehicle Technology. The worldwide status of the research is introduced together with proposals related to the design and development of such vehicles from aerodynamics, flight mechanics, material sciences, and structures points of view. Part I introduces the morphing concept and its potential. Part II summarizes the present technological level, while Part III discusses technological challenges and solution proposals. I.

This study presents a hierarchical analysis framework to examine the stress-strain distributions in notched fiber-reinforced ceramic-matrix composite (CMC) laminates and correlates microstructural variability with macroscopic mechanical responses. Hierarchical models are employed, including a finite element (FE) model incorporating an inelastic constitutive model for CMC laminates, an analytical model that captures inelastic deformation resulting from matrix cracking and a micro-mechanical model developed to assess fiber break displacement due to fiber failure, accounting for the interfacial shear response between fibers and the matrix. Both the analytical and FE models produce accurate stress predictions; however, the results are nonconservative. The strain predictions are validated against digital image correlation data under moderate strain conditions, with the analytical model providing more conservative strain estimates. A domain map of the elastic-inelastic transition near the notch edge, as a function of applied stress and notch size, is presented to assist in predicting stress and strain distributions. Simultaneous analysis of stress and strain distributions reveals that inelastic strains in the concentration region reduce peak stresses, thus mitigating stress concentration. Quantitative analysis of microstructural features using X-ray tomography demonstrates a strong correlation between microstructural variations and the stress state in the stress concentration region of the notched CMCs. The results indicate that hierarchical analytical modeling correlates stress distributions with the microstructure ahead of notches, offering new insights into the behavior of the notched CMCs.

The aim of this study was to determine and compare the linear dimensional changes, and water sorption of a denture base polymer reinforced with chopped glass fiber and metal filler. The dimensional changes were measured immediately after processing, after 1, 2, 3, 7 and 14 days of water storage. The results revealed that both types of reinforcement affect the dimensional accuracy and water sorption of the test specimens. The greatest dimensional accuracy was found with the glass fiber reinforced test specimens. The lowest amount of water sorption was found with the metal-filled test specimens. It was concluded that, metal fillers decreased the water sorption of the resin material greater than the effect of glass fibers, while the glass fibers showed marked reduction in the linear dimensional changes of acrylic resin than that of the metal fillers. The glass fibers and metal fillers can be clinically used as a denture base reinforcement.

The use of laser light for bonding of continuous fiber reinforced thermoplastic composites (CFTPC) offers new possibilities to overcome the constraints of conventional joining technologies. Laser bonding is environmentally friendly as no chemical additive or glue is necessary. Accuracy and flexibility of the laser process as well as the quality of the weld seams provide benefits which are already used in many industrial applications. Laser transmission welding has already been introduced in manufacturing of short fiber thermoplastic composites. The laser replaces hot air in tapelaying systems for pre-preg carbon fiber placement. The paper provides an overview concerning the technical basics of the joining process and outline some material inherent characteristics to be considered when using continuous glass fiber reinforced composites The technical feasibility and the mechanical characterization of laser bonded CFTPC are demonstrated. The influence of the different layer configurations on the laser interaction with the material is investigated and the dependency on the mechanical strength of the weld seem is analyzed. The results show that the laser provides an alternative joining technique and offers new perspectives to assemble structural components emerging in automotive or aeronautical manufacturing. It overcomes the environmental and technical difficulties related to existing gluing processes.

This paper investigates the manufacturing and mechanical properties of thermoplastic composite-metal hybrid laminates based on DP500 steel sheets bonded to a glass fiber-reinforced polypropylene (PP) or to a self-reinforced PP composite materials. Single cantilever beam (SCB) tests revealed that a good level of adhesion can be achieved by using a hot dip zinc surface treatment on the DP500 steel and incorporating an interlayer based on modified polypropylene at the interface between the composite and metal plies. In addition, SCB tests have shown that the interfacial fracture energy of the hybrid laminates increased with increasing crosshead displacement rate. Additional testing of a number of laminates has shown that the tensile properties of these composite-metal hybrid laminates are strongly dependant on the tensile properties of the constituent materials and that a modified rule of mixtures could be used to predict such properties.

Equipment in high voltage power systems can be protected effectively by metal oxide surge arresters. Basically two different types of surge arresters are used: surge arresters with air insulation using porcelain or polymeric housings (AIS surge arresters) and surge arresters with SF6-insulation using a metallic housing (GIS surge arresters). The probability of a failure of a GIS surge arrester shall be considerably less than for an air insulated surge arrester. Failures of GIS equipment always will result in major outages and costly corrective maintenance. Potential sources of surge arrester failures are the metal oxide (MO) resistor, insulating parts as fiber reinforced (FRP) rods and partitions and the metal enclosure. MO resistors are not allowed to show any aging und must have a high energy discharge capability. The FRP-rods must be free of partial discharges and must withstand high electrical strength. The metal enclosure must be made of high quality material as well as the manufacturing process shall be of high standard including sufficient testing and final certification. Required routine testing on the completely assembled surge arrester does not suffice rather all parts used must be routine tested in a proper way to avoid failing within the life time of more than 30 years. In case of a failure caused by overloading the destruction must be limited to the surge arrester. Index Terms overvoltage, metal oxide surge arrester, design, metallic tank, insulating part, failure, quality

In this paper, the one-dimensional tensile behavior of Guadua angustifolia Kunth fibre/polypropylene (PP+GAKS) composites is modeled. The classical model of Kelly–Tyson and its Bowyer–Bader’s solution is not able to reproduce the entire stress–strain curve of the composite. An integral (In-Built) micromechanical model proposed by Isitman and Aykol, initially for synthetic fiber-reinforced composites, was applied to predict micromechanical parameters in short natural fiber composites. The proposed method integrates both the information of the experimental stress-strain curves and the morphology of the fiber bundles within the composite to estimate the interfacial shear strength (IFSS), fiber orientation efficiency factor ηFOD, fiber length efficiency factor ηFLD and critical fiber length lc. It was possible to reproduce the stress-strain curves of the PP+GAKS composite with low residual standard deviation. A methodology was applied using X-ray microtomography and digital image proces...

Investigate the effect of aluminum oxide air abrasion, used for cleaning the surface of human dentin, on the bond strength to resin cements for indirect restorations. Data and source: This study followed PRISMA-ScR guidelines for scoping reviews and registered on the Open Science Framework platform. Study selection: A comprehensive search of four electronic databases: PubMed, Scopus, Embase, and Web of Science, as well as manual searches, was performed to identify relevant studies published through July 2024. Studies focused on in vitro evaluations of oxide particles as a surface cleaning method for sound human dentin and their effect on the bond strength of resin cements for indirect restorations were included. Studies involving glass ionomer cements and temporary cements were excluded. Results: A total of seven (7) studies were included in the descriptive analysis and meta-analysis. The overall metaanalysis of air abrasion with aluminum oxide particles (50 µm) showed a statistically significant difference (SMD: 0.94, 95 % CI, 0.43-1.46), favoring the air abrasion group. Additionally, when comparing pumice with air abrasion using aluminum oxide particles, a significant difference was found (SMD: 0.94, 95 % CI, 0.43-1.46), favoring the air abrasion group. The meta-analysis evaluating substrates with immediate dentin sealing (IDS) and air abrasion with alumina particles showed a significant difference in favor of the control group (IDS only -no cleaning method) (SMD: SMD: 0.62, 95 % CI, 1.10-0.15). Conclusion: Dentin cleaning with 50 µm aluminum oxide particles significantly improves the bond strength to resin cement. In addition, air abrasion provides higher resin cement bond strength than pumice and water cleaning. However, on substrates treated previously with immediate dentin sealing, air abrasion reduced the resin cement bond strength compared to the no cleaning method. Clinical Significance: Air abrasion with 50 µm aluminum oxide particles may improve the bond strength of resin cements to sound dentin, supporting its use before cementing indirect restorations. However, when used after immediate dentin sealing, this technique may impair bond strength and should be avoided in such cases.

Solid particle erosion of polymer composites is a complex surface damage process, strongly affected by material properties and operational conditions. The present research work is undertaken to study the development, characterization and erosion wear performance of two different categories of fibers when reinforced in polymers. One of the two fiber is well known synthetic fiber i.e. glass fiber which is commercially used by many industries and the other fiber will be a natural fiber i.e. banana fiber which will be the new attempt in the present investigation. In both the above cases matrix material will remain epoxy. From the performed experiments it can be seen that a banana fiber can successfully replace the glass fiber as far as wear performance in concerned, as the study indicates that erosion wear performance of banana fiber based composites is better than that of the glass fiber reinforced composites. Banana fiber is also having a very low specific gravity, so their composites...

This research investigation focuses on finite element modeling of carbon nanotube (CNT) reinforced concrete matrix for three grades of concrete namely M40, M60 and M120. Representative volume element (RVE) was adopted and one-eighth model depicting the CNT reinforced concrete matrix was simulated using FEA software ANSYS17.2. Adopting random orientation of CNTs, with nine fibre volume fractions from 0.1% to 0.9%, finite element modeling simulations replicated exactly the CNT reinforced concrete matrix. Upon evaluations of the model, the longitudinal and transverse Young’s modulus of elasticity of the CNT reinforced concrete was arrived. The graphical plots between various fibre volume fractions and the concrete grade revealed simplified equation for estimating the young’s modulus. It also exploited the fact that the concrete grade does not have significant impact in CNT reinforced concrete matrix.

Resumo: O presente trabalho descreve os processos de obtenção de compósitos termoestruturais de carbono reforçado com fibras de carbono. O processamento desses materiais tem início pela definição de uma arquitetura do reforço de fibras de carbono, seja na forma de empilhamento simples do reforço, de tecidos ou na forma de reforço multidirecional. A incorporação de matriz carbonosa no reforço de fibras, pelo preenchimento de vazios e interstícios, promove a densificação do material, e o incremento de massa específica. Duas rotas de processamento são predominantes na obtenção desses materiais, o processo via impregnação líquida e o processo via impregnação em fase gasosa. Em ambos os casos, processos térmicos levam à formação de matriz de carbono com propriedades específicas, que derivam de seus materiais precursores. Os processos diferem entre si, também, pelo rendimento, enquanto os processos executados por impregnação líquida apresentam rendimento de, aproximadamente, 45%, os processos por impregnação em fase gasosa apresentam rendimento em torno 15%.

Fabrication of an appropriate scaffold is critical in order to recapitulate the architecture and functionality of the native tissue. In this study, we attempted to create favorable collagen fiber alignment and multilamellar with uniaxially oriented layers, using a disc collector by turning mats 90 degrees horizontally at specific times. Different concentrations of rat tail-derived type I collagen (3, 6, 8% w/v) in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) are used for electrospinning affairs. The 6% w/v collagen at an applied voltage of 20 kV and collector rotation of 2500 rpm was selected to exhibit bead-free homogeneous nanofiber with fiber thickness of 0.14 ± 0.4 µm, maximum thickness of 0.5 ± 0.08 µm, and 60% porosity. Also, scanning electron microscope images of electrospun fibers showed 3D multilamellar scaffold with the goodness of 96.5% ± 0.8 in each aligned uniaxially oriented fiber layer. Cross-linking of collagen fibers with N-(3-dimethylaminopropyl)-N0-ethylcarbodiimide h...

We establish, by means of a large class of continuous t-representable intuitionistic fuzzy t-conorms, a factorization of an intuitionistic fuzzy relation IFR into a unique indifference component and a family of regular strict components. This result generalizes a previous factorization obtained by Dimitrov 2002 with the max,min intuitionistic fuzzy t-conorm. We provide, for a continuous t-representable intuitionistic fuzzy t-normT, a characterization of theT-transitivity of an IFR. This enables us to determine necessary and sufficient conditions on a T-transitive IFR R under which a strict component of R satisfies pos-transitivity and negative transitivity. Copyright q 2009 Louis Aime ́ Fono et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1.

We establish, by means of a large class of continuous t-representable intuitionistic fuzzy t-conorms, a factorization of an intuitionistic fuzzy relation IFR into a unique indifference component and a family of regular strict components. This result generalizes a previous factorization obtained by Dimitrov 2002 with the max,min intuitionistic fuzzy t-conorm. We provide, for a continuous t-representable intuitionistic fuzzy t-normT, a characterization of theT-transitivity of an IFR. This enables us to determine necessary and sufficient conditions on a T-transitive IFR R under which a strict component of R satisfies pos-transitivity and negative transitivity. Copyright q 2009 Louis Aime ́ Fono et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1.

This paper present two parameters Weibull analysis result on mechanical properties of kenaf fiber under different condition of alkali treatment. The mechanical properties of kenaf fiber that as focused in this study was fiber matrix interfacial shear strength (IFSS) and fiber tensile strength (TS). Kenaf fiber were treated under various conditions alkali concentration at 2, 6 and 10 (w/v%), immersion duration at 30, 240 and 480 minute and immersion temperature at 27, 60 and 100oC. Unsaturated polyester matrix was used in this study to determine the interfacial shear strength (IFSS). The result shows that Weibull modulus of kenaf fiber interfacial shear strength (IFSS) at 30 minutes immersion duration value was 2.59 to 3.12 with characteristic strength, σo-IFSS value range was 0.29MPa to 0.37MPa. The highest Weibull modulus was at room temperature and 6% alkali concentration. For kenaf fiber tensile strength Weibull modulus, the range was 2.40 to 3.07 with characteristic strength value range from 345MPa to 597MPa. The highest Weibull modulus also was measured at room temperature and 2% alkali concentration. The characteristic strength value shows a degrading pattern with the increment on immersion temperature and alkali solution concentration.

The processing of fiber-reinforced thermoplastics is often accompanied by a significant fiber fracture. Therefore, it is important to assess the effect of processing variables on the extent of fiber damage occurring during product fabrication, such as extrusion or injection molding. The present paper discusses fiber damage caused by shear forces exerted on the composite by a molten matrix in both experimental and theoretical terms. The degradation process in carbon fiber-polypropylene composites is studied in a broad range of shear rates, although it occurs significantly only under high shearing in a capillary. Changes in fiber length and its distribution during the multi-flow through a capillary, as well as the materials' rheological properties found in research after shearing, are discussed and the results are compared with a model of fiber-length analysis for the mixing-regrinding process.

Effect of fiber addition on mechanical and durability characteristics of SCC was evaluated. Effect of early wetting/drying cycles on FRSCC mechanical properties was investigated. Microstructural analysis of FRSCC and correlation with macro-properties was conducted. Low chloride permeability was achieved confirming adequate durability of FRSCC.

The aim of this paper is to present a study on the relationship between crack geometrical properties (width and area) and water permeability evolution in a cracking saturated concrete sample. The tensile splitting (Brazilian) test is enhanced and adapted so that the monitoring of a single crack opening of the specimen and the water-flux through the crack is possible. The complete description of the crack geometry is firstly obtained. The crack opening displacement (CODm) at mid-height of the sample is derived from LVDTs measurements while the crack path on the whole height is obtained by means of the digital imaging correlation (DIC) technique. For both sides of the sample the complete description of the displacement field is obtained. The COD all along the path of the crack is then computed and a statistical relationship between the computed mean crack area and measured CODm is developed. This relationship is used, during the second series of tests, to relate at each time step of t...

The use of composite materials is an effective technique to enhance the capacity of reinforced concrete columns subjected to the seismic loading due to their high tensile strength. In this paper, numerical models are developed in order to predict the experimental behavior of square reinforced concrete columns strengthened by glass fiber reinforced polymer and steel bars and unstrengthened column under cyclic and monotonic loadings, respectively. Two columns are modeled in the present work. The first one corresponds to the column without strengthening subjected to lateral monotonic loading, and the second one corresponds to the column strengthened by glass fiber reinforced polymer and steel bars subjected to lateral cyclic loading. Comparison of the numerical modeling and the experimental laboratory test results are performed and discussed. A good agreement between the numerical and experimental force-displacement responses is obtained. Moreover, improvements in the strength of the reinforced concrete column subjected to the cyclic loading along with the comparison of the behavior of the strengthened column with the unstrengthened reference column are discussed. The results show a good improvement in the load carrying capacity and ductility of the column. The main objectives of this numerical modeling are to contribute the comprehension of the monotonic and cyclic behavior of the square reinforced concrete columns and to compare the numerical results with the experimental ones.

Nylon 6 and 66 were toughened with EPDM-g-MA and SEBS-g-MA and steady-state rheological behaviour of rubbers, nylons and their blends and mechanical properties of nylons and their rubber-toughened blends were investigated. The EPDM maleic grafting preparation was ...

The simultaneous use of different types of fibers as reinforcement in cementitious matrix composites is typically motivated by the underlying principle of a multi-scale nature of the cracking processes in fiber reinforced cementitious composites. It has been hypothesized that while undergoing tensile defor-

The fracture process zone encloses relevant mechanisms which explain the quasi-brittle behavior of cementitious composites. It is an important concept in non-linear fracture mechanics and in the simulation of cracking processes. The use of fibers as reinforcement may alter the crack initiation and propagation processes. A better understanding of the microcracking mechanisms taking place at the level of the fracture process zone is therefore relevant for an optimized design of these materials, as well as for the simulation of their mechanical behavior. In this study, the use of an image analysis procedure to capture the crack initiation and propagation process in concrete and other cementitious composites is described. It utilizes high resolution digital images of the surface of the specimens while undergoing the cracking process to determine the displacement fields. The formed cracks are observed at a relatively small scale, allowing the investigation and analysis of propagating cracks near the crack tip in specimens of concrete and other cementitious composites.

This article presents the results of a study of the processing and physicomechanical properties of environmentally friendly wood‐fiber‐reinforced poly(lactic acid) composites that were produced with a microcompounding molding system. Wood‐fiber‐reinforced polypropylene composites were also processed under similar conditions and were compared to wood‐fiber‐reinforced poly(lactic acid) composites. The mechanical, thermomechanical, and morphological properties of these composites were studied. In terms of the mechanical properties, the wood‐fiber‐reinforced poly(lactic acid) composites were comparable to conventional polypropylene‐based thermoplastic composites. The mechanical properties of the wood‐fiber‐reinforced poly(lactic acid) composites were significantly higher than those of the virgin resin. The flexural modulus (8.9 GPa) of the wood‐fiber‐reinforced poly(lactic acid) composite (30 wt % fiber) was comparable to that of traditional (i.e., wood‐fiber‐reinforced polypropylene) c...

Concrete with no slump that is typically used for prefabrication is known as zero slump concrete (ZSC). ZSC is sensitive to mixture proportion. Since coarse aggregate makes up the majority of the concrete volume, recycling concrete aggregates will be a great choice for reducing the amount of concrete waste. Therefore, the purpose of this paper is to analyze the impact of using coarse recycled concrete aggregate (RCA) in ZSC properties. Five mixes were manufactured, each with a different percentage of coarse RCA (0%, 25%, 50%, 75%, and 100%). Compressive strength, flexural strength, ultrasonic pulse velocity (UPV), dry bulk density, and water absorption of recycled aggregate ZSC were conducted at 7, 28 and 90 days. Experiments revealed that the inclusion of coarse RCA in ZSC degraded the quality of manufactured concrete. At 90 days, in comparison to the control mix, the minor drop was at 25% coarse RCA incorporation, which resulted in a 6.2%, 4.1%, 2%, and 2.4% drop in compressive strength, flexural strength, UPV, and dry bulk density, respectively, while there was a 24.4% increase in water absorption. The highest drop of recycled aggregate ZSC at 100% incorporation resulted in a 41.7%, 19.1%, 8.6%, and 7.6% drop in compressive strength, flexural strength, UPV, and dry bulk density, respectively, while there was a 158.8% increase in water absorption

The available methods for veneer evaluation are limited to clinical and radiographic examinations, which may not allow the appropriate identification of failure. In this report, we demonstrate the use of optical coherence tomography (OCT) as a noninvasive diagnostic and follow-up method to evaluate gingival recovery and the adhesive interface in aesthetic oral rehabilitation involving periodontal plastic surgery and ceramic laminate veneers. OCT was efficient for evaluating both soft and hard tissues, as well as the quality of the adhesive interface. In conclusion, OCT was found to be a promising approach for the professional evaluation of aesthetic oral rehabilitation, as it was capable of generating images that enabled the analysis of gingival recovery and the adhesive interface.

The wide use of composite materials is mainly due to their excellent strength / mass ratio, corrosion resistance and relatively low price. Approximately 35-40% of the fibre-reinforced composites are made of thermoplastic polymers in which fibreglass, carbon or natural fibres are most often used as reinforcement, while the remaining 60 -65% is made up of high-tech carbon or glass fibre-reinforced thermosetting composites. Most of them are used in the transport and electronics industries. New processing technologies not only improve the properties of the products but also contribute to reducing costs. In this paper, we compare the results of mechanical tests with molded standard specimens with polypropylene matrix and test results from cut-outs from injection molded products.

Objetive: This research aimed to verify the performance of thermally activated acrylic resin (TAAR) combined with a mix of glass and aramid fibers and/or composite resin of indirect use by a tree point bending test. Material and Methods: Ten samples, with 65 x 10 x 2.5 mm, were prepared for each group (n = 10): CO, control of only TAAR; CR, in which an 60 mm indirect composite resin was polymerized together with the acrylic resin during the thermo-polymerization cycle; SS, in which ceramic glass mixed with aramid fibers cut 60 mm in length were incorporated into the samples; and SC, in which the same fibers were incorporated with addiction of the indirect composite resin. A three-point flexural strength test was performed with a universal testing machine with a load of 50KgF at a speed of 5 mm/min in the center of the samples supported by a suitable device. The reinforced face was placed to the tensile side. The statistical one-way ANOVA and Tukey tests were made with a significance...

Windows are points of the lowest resistance in the total sound and heat insulation of buildings. To enhance both thermal and acoustical qualities of windows with insulating glass units (IGU), the gaps between the panes can be filled with a heavier-than-air gas alone (for example, argon, krypton, xenon, and sulfur hexafluoride) or mixed with air. Here, the sound transmission loss (STL) may be increased in the low-frequency range dominated by acoustic resonances where the panes and gaps play the role of masses and springs. This frequency region (typically 100-500 Hz) is important for reducing traffic noise by windows. However, the expected acoustical improvement is often not measured using the standard two-reverberation room techniques. In this paper, such a discrepancy is theoretically and experimentally studied for physical interpretation and design optimization. Clear closed-form expressions have been derived and verified for the direct (via the panes and gaps) and flanking (via the panes and perimeter structural links) sound transmission through single-space and double-space insulating glass units, and improvement proposals have been developed. The results can be interesting for the scientists and engineers engaged in acoustics and construction.

A series of non-destructive tests such as Radiation Thermometer, Electromagnetic Radar, Impact Echo Scanner, Concrete Test Hammer, Scratch Tester, Windsor Pin System, and Electromagnetic Induction Scanner are carried out for diagnostic inspection of deterioration on the Sanctuary of Vicoforte. In this paper, 1) Delamination of stone finishing and fresco painting, 2) Thickness of main dome and vaults above chapels, 3) Detection of reinforcement, 4) Continuity of iron ties, 5) Subsidence of ground level, 6) Fundamental frequency of the dome, and 7) Estimation of compressive strength and Young's modulus of the brick are discussed.

In this study, analytical models considering different material and geometry for ‎both single and double-lap bolted joints were reviewed for better understand how to ‎select the proper model for a particular application. The survey indicades that the ‎analytic models selected for the adhesively single or double bolted lap joints, as well ‎as T, scarf, and stepped joints, with linear material properties are mostly two ‎dimensional and the studies on stress distribution and/or failure of the joint are ‎performed either experimentally, analytically or by finite element method. The results ‎seem to be generally accurate and adequate. Additionally, it was shown that any ‎increase in the bolt-hole clearance leads to an increase in bolt rotation, as well as a ‎decrease in bolt-hole contact area, and hence, a reduction in joint stiffness. Moreover, ‎studies on hybrid joints have revealed that the proper choice of adhesive material in ‎conjunction with bolts or rivets in a joint, allows for significant increase in the static ‎and fatigue strength compared to similar pure bonded joints. Additionally, the results ‎on hybrid scarf joints showed that it is vital to place fasteners closer to the ends of the ‎overlap to suppress the peak peeling stresses and hence, delay the effects of early ‎crack initiation in the adhesive layer...

Alkali-activated composites are significant materials in reducing CO2 emis-
sions and ensuring sustainability. With the increasing concerns about cli-
mate change globally, the interest in alkali-activated materials has also
increased. Researching different fibers has very important potential in this
area. This study aims to make alkali-activated concretes widespread in the
concrete sector by using the materials common in conventional concretes
and ensuring that alkali-activated concretes are an alternative in terms of
sustainability. Experimental studies were conducted to examine the mech-
anical, durability, and microstructural properties (SEM) of slag-based alkali-
activated concrete (AASC) reinforced with three various fibers. The fibers,
polypropylene (PP), polyamide (PA), and steel (ST), were used with two
ratios (%0.4 and %0.8 by vol.). Compressive, splitting tensile, and flexural
strength tests were carried out at 28 and 90 days. In terms of durability
properties, the samples were exposed to high temperatures
(300–600–900 C) and freeze-thaw test (250 cycles). The results showed
that the addition of fibers improved the strength and durability properties;
for instance, the existence of steel and polypropylene fibers increased the
flexural toughness factor values by 430% and 260%, respectively.
Moreover, the compressive strength of the fibrous samples exposed to
900 C was obtained in the range of 6-23 MPa.

A boundary layer theory for the buckling and postbuckling of anisotropic laminated thin shells is extended to the loading case of torsion. A singular perturbation technique is employed to determine the buckling load and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling behavior of twist, perfect and imperfect, anisotropic laminated cylindrical shells with different values of shell parameters and stacking sequence. The new finding is that there exists a shear stress along with an associate compressive stress when the anisotropic shell is subjected to torsion, and all the results published previously need to be re-examined. The results confirm that the effect of the boundary layer on the solution of a twist shell is of the order e 5/4 . The postbuckling equilibrium path is unstable for the moderately long shell subjected to torsion and the shell structure is less sensitive to initial imperfections than in the case of axial compression.

We investigate the evolution and propagation of cracks in 2-d elastic domains, which are subjected to quasi-static loading scenarios. In addition to the classical variational formulation, where the standard potential energy is minimized over the cracked domain under physical conditions characterizing the behavior of the material close to the crack (e.g. nonpenetration conditions), we include a 'cohesive traction term' in the energy expression. In this way we obtain a mathematically concise set of partial differential equations with nonlinear boundary conditions at the crack interfaces. We perform a finite element discretization using a combination of standard continuous finite elements and so-called cohesive elements. During the simulation process cohesive elements are adaptively inserted at positions where a certain stress bound is exceeded. In our numerical studies we consider domains consisting of a matrix material with fiber inclusions. Beyond pure crack path simulation, our ultimate goal is to determine an optimal shape of the fibers resulting in a crack path that releases for a given load scenario as much energy as possible without destroying the specimen completely. We develop a corresponding optimization model and propose a solution algorithm for the same. The article is concluded by numerical results.

Shear behavior of reinforced concrete beams using steel lathe scrap waste and end hooked
steel fibers as fully or partially web shear reinforcement replacement was studied. Steel lathe scrap
waste is generated from industrial steel waste and can be used as recycled fibers offering additional
advantages towards environmental pollution reduction. To investigate their effect of reinforced
concrete beam under shear behavior, ten reinforced concrete beam specimens with 1200 mm long,
200 mm wide, and 300 mm high were tested under quasi-static loading (two-point loading). The
studied parameters in this investigation were types of fibers such as steel lathe waste fiber and
traditional hooked steel fiber ratio and the web shear reinforcement ratio are zero% and 50%. Results
observed were initial and post-cracking stiffness, maximum capacity load, vertical displacements,
modes of failures, and the ductility of the specimens. It was concluded that using of steel lathe scrap
waste and hooked steel fibers in concrete are advantageous, they changed the mode of failure of the
beam from a brittle to a ductile mode of failure due to the ductility of steel used, whether traditional
steel fiber or steel lathe waste fiber. The optimum ratio of the steel lathe scrap waste was found equal
0.5% while the optimum ratio of traditional hooked steel fiber is 1% as fractional volume.