Innovative Composite Materials Research Articles

Applications of innovative composite materials for seismic strengthening of masonry structures

Masonry buildings are prone to brittle collapses under seismic forces due to their fragility and low capacity to resist against cyclic actions. In most cases failures occur in forms of rigid collapses due to loss of equilibrium of entire structural parts, and this is due to low quality of structural detailing or horizontal forces due to vaults and arches that increase their intensity during earthquakes.The entire architectural heritage is represented by masonry construction, also in seismic areas, thus a mandatory issue consists of preserving the historical value against natural events such as earthquakes. In the last years new materials were employed as strengthening systems for structural purposes, and composite materials are those that have found a large field of application in this context. New structural solutions for seismic strengthening and retrofit are presented in the paper, with reference to real applications in which composite materials demonstrated to be effective solutions.The applications will be presented with reference to two historical masonry buildings, having different construction schemes; in which pre tensioned FRP wires were designed and applied as ties. The use of FRP wires for the first building was studied with reference to the existing cracking problems, which were investigated by means of non-destructive techniques, visual inspections and local destructive tests. The second case reports a study of seismic vulnerability for a large building used as theatre, in which a global analysis was accompanied by kinematic analyses that were run under linear and non- linear approaches. The results of the analyses allowed understanding the possible failure mechanisms that needed to be inhibited by an effective structural strengthening system. Also in this case the use of FRP pre-tensioned wires, about 40 m long, demonstrate to be the most effective structural device in terms of costs and speed of application.The seismic analyses (global and local) will be illustrated and discussed in the paper, with reference to the experimental tests that were necessary for the characterization of the material properties. The results will show how the presence of the FRP system is able to prevent possible collapses of the high walls that are present in the building.

1 of 1 Experimental and FE simulations of ferrocement columns incorporating composite materials

This paper presents a proposed method for producing reinforced composite concrete columns reinforced with various types of metallic and non metallic mesh reinforcement. The experimental program includes casting and testing of twelve square columns having the dimensions of 100 mmx100 mmx1000 mm under concentric compression loadings. The test samples comprise all designation specimens to make comparative study between conventionally reinforced concrete column and concrete columns reinforced with welded steel mesh, expanded steel mesh, fiber glass mesh and tensar mesh. The main variables are the type of innovative reinforcing materials, metallic or non metallic, the number of layers and volume fraction of reinforcement. The main objective is to evaluate the effectiveness of employing the new innovative materials in reinforcing the composite concrete columns. The results of an experimental investigation to examine the effectiveness of these produced columns are reported and discussed including strength, deformation, cracking, and ductility properties. Non-linear finite element analysis; (NLFEA) was carried out to simulate the behavior of the reinforced concrete composite columns. The numerical model could agree the behavior level of the test results. ANSYS-10.0 Software. Also, parametric study is presented to look at the variables that can mainly affect the mechanical behaviors of the model such as the change of column dimensions. The results proved that new reinforced concrete columns can be developed with high strength, crack resistance, and high ductility properties using the innovative composite materials.

Application of Innovative Composite Cool Thermal Insulating Material for the Energy Upgrade of Buildings

The need to improve energy efficiency of existing buildings is more than understandable and compelling. It is expressed through the EU Directive 2002/91/EU concerning the energy performance of buildings, the Greek Law 3661/08 concerning the improvement of the energy performance of buildings; which constitutes the harmonization of the Directive in the Greek legislation as well as the Regulation on Energy Efficiency Buildings (KENAK) which together with the Technical Instructions of the Technical Chamber of Greece, are the main application of the Legislation.The composite cool materials are a new and interesting solution for the constructions. Having identified -with extensive bibliographic research- the existing state of the market for thermal insulation materials and trends, these composite materials were characterized as a successful option. Finally, external thermal insulation composite systems were produced (with photocatalytic coating) and composite materials for the roof (extruded polystyrene with low reflectivity ceramic tile) which were analyzed -initially theoretically- in order to determine the energy performance of the building before and after their application, and then applied to an existing building.Additionally, there were determined the conditions before and after the installation of materials for thermal insulation capacity, by measuring the rate of heat transfer, by conducting measurements for the evaluation of the implementation of the new products of thermal comfort and air quality as well as by representative measurements of the microclimate of the area both during summer and winter. The results of the energy performance of new materials after their first application are to be presented

Experimental and numerical analysis of aramid fiber laminates with DCPD resin matrix subjected to impact tests

Research for innovative composite material solutions for impact absorbers is focused on the analysis of their ability to absorb impact energy. For this purpose, aramid fiber laminate with DCPD resin matrix was prepared. Laminate samples were tested on the drop test and were subjected to ballistic loads. The laminate structure was modeled with ABAQUS software with the objective to optimize and estimate the ability to absorb impact energy in the range of high speeds (350m/s).

Preparation and Properties of NrGO-CNT Composite for Lithium-Ion Capacitors

The lithium-ion capacitor (LIC), combining the advantages of lithium-ion batteries and supercapacitors, has gained significant attention as a new class of energy storage system. Typically, the LIC consists of graphite as the negative electrode and activated carbon (AC) as the positive electrode, while the energy density is limited by the low capacitance of the positive electrode. In this study, an innovative composite material of nitrogen-doped reduced graphene oxide (NrGO) chemically bonded with carbon nanotubes (CNTs), denoted [NrGO-CNT], is designed to circumvent this issue. The [NrGO-CNT] composite possesses not only high electrical conductivity but also high specific surface area and well-distributed mesopores and micropores. The LIC employing [NrGO-CNT] composite shows a cell capacitance retention of 93.5% after 1000 cycles at a scan rate of 200 mV s−1, revealing high cycling stability. This LIC delivers a high specific energy of 124.9 Wh kg−1 at a specific power of 1.26 kW kg−1 at the cell voltages between 1.5 and 4.5 V. Consequently, the [NrGO-CNT] composite is a promising electrode material for high-performance LICs.

Photolithography of 3D Scaffolds for Artificial Tissue

The present study is focused on the design and fabrication of novel functional 3D-hydrogel scaffolds for regenerative medicine. In order to critically analyzing the effect of the microarchitecture of 3D scaffolds for driving the cellular fate and diffusion of progenitor stem cells we have fabricate a number of scaffolds with different geometry, stiffness and composition. The physical characteristics of the scaffold determine indeed, as well the biochemical factors, the fate of the cells. We use an innovative composite material consisting of hydrogel with different molecular weight and with suitable accordion-like and woodpile structures in order to tailor stiffness and elasticity conferred to the final structure.These novel 3D bioinspired scaffolds were obtained by both single- (1PP) and two-photon polymerization (2PP) processing. In particular, 2PP scaffolds represent a great advantage with respect to previous achievements based on traditional methods. 3D-structures were fabricated with lateral resolution of some microns, allowing an advanced control of pore microarchitecture of defined tensile strength, and the inclusion of albumin microspheres with various functionalities. The morphological, biochemical and functional characteristics are discussed. Moreover, the effects of the structured hydrogel scaffolds on the proliferation and differentiation of adult stem cells is analyzed in view of the fabrication of portion of contractile cardiac muscle to be obtained In Vitro.

Mechanical characterization and modeling of an innovative composite material for railway applications

The innovation in the railway industry is focused on the production of lightweight vehicles with high performance, in order to obtain an energy power saving and to satisfy the environmental and global community requests. To pursue this aim, new materials have been increasingly used for vehicle structures. The selection of innovative materials and the definition of the relative properties represent, however, one of the most critical aspects for the design. Several factors, such as technical requirements, strength- and stiffness-to-weight ratios, crash resistance, and cost, are involved in material selection for rail vehicles. In addition, materials have to be chosen in accordance with the reference standards concerning fire resistance. This paper describes the activity carried out in order to acquire the needed information about selected composite materials to be used in the design and validation phases for a structural rail vehicle end and a roof. The material under investigation has been manufactured in order to satisfy the strict railway light metro fire normative. Due to the novelty of the adopted composite materials, a full mechanical characterization of the lamina was needed. The orthotropic material properties were verified and tuned using further tests on laminate and sandwich configurations in order to take into account, also, the influence of manufacturing process parameters. Analytical and numerical approaches have been used to validate and optimize the structural layout. Results of the multistep material characterization, acquired during the above phases, have been used to perform computational analysis in order to further improve the component design.

Development of fine grained concretes for textile reinforced cementitious composites

A new innovative composite material is textile reinforced cementitious composite (TRCC). To achieve high flexural performance researchers suggest polymer modification of TRCC matrices. In this study, nine ready mix repair mortars commonly used in construction industry and the production of TRCC elements were examined. Mechanical properties such as compressive and flexural strength, drying shrinkage were studied. Being a significant durability concern, alkali silica reaction tests were performed according to related standards. Results showed that, some ready repair mortar mixes are potentially reactive due to the alkali silica reaction. Two of the ready mortar mixes labelled as non-shrinkage in their technical data sheets showed the highest shrinkage. In this experiment, researchers designed new matrices. These matrices were fine grained concretes modified with polymer additives; latexes and redispersible powders. Two latexes and six redispersible powder polymers were used in the study. Mechanical properties of fine grained concretes such as compressive and flexural strengths were determined. Results showed that some of the fine grained concretes cast with redispersible powders had higher flexural strength than ready mix repair mortars at 28 days. Matrix composition has to be designed for a suitable consistency for planned production processes of TRCC and mechanical properties for load-carrying capacity.

Fatigue and Flexural Behavior of Reinforced-Concrete Beams Strengthened with Fiber-Reinforced Cementitious Matrix

AbstractThe need for repair and rehabilitation is a crucial issue today in order to maintain a safe and efficient transportation network. One of the most recent innovative composite materials that has been proposed to the market is a fabric reinforced cementitious matrix (FRCM) strengthening system. This system consists of two components: a structural reinforcement mesh and a cementitious matrix. The structural reinforcement mesh consists of a polyparaphenylene benzobisoxazole (or PBO) fiber composite, while the cementitious matrix is a nontoxic grout system based on portland cement with a low dosage of dry polymers. The first aim of this study was to evaluate the fatigue resistance of reinforced concrete (RC) beams strengthened with FRCM under fatigue loading and postfatigue flexural strength to failure. The second aim was to investigate the durability performance of the FRCM after exposure to environmental conditioning including temperature, moisture, and sustained stress. All of the beam specimens exam...

Mechanical Properties of Metal-Plastic Composite with Internal Fractal Shape Reinforcing Structure

This paper deals with mechanical properties research of innovative polymer multiphase metal and polymer composite materials consisting of matrix and isotropic or anisotropic oriented deterministic fractal shapes made by 3D printing. By creating of reinforcing internal structure consisting of deterministic fractal connected shapes is possible to gain unlimited mechanical properties directing. These fractal shapes - placed in multiphase system matrix – are significantly influencing whole material system mechanical properties mainly in case of stress on the limit of strength, proportional elongation on the limit of strength or tensile/ flexural modulus. Fractal shapes are also possible to properly locate, orient or shape modify according to potential material using with goal to gain maximal efficiency of fractal shapes occurrence. Producing of this multiphase system is realized by the help of 3D printing technology. Internal fractal shape structure is 3D printed from aluminium. This feature is in the next step over injected by polymer. So is possible to create any fractal shapes placed in polymer matrix which are by another technology unmanufacturable. Mechanical properties analyse is performed with respect to fractal shape type, fractal dimension, and fractal shape orientation.

Effect of Porous Activated Charcoal Reinforcement on Mechanical and In-Vitro Biological Properties of Polyvinyl Alcohol Composite Scaffolds

The present work focused on developing an innovative composite material by reinforcing polymer matrix with highly porous activated charcoal. Polyvinyl alcohol-activated charcoal (PVA-AC) composite scaffolds were developed by varying the AC concentrations (0, 0.5, 1, 1.5, 2 and 2.5 wt%) in PVA matrix by freeze drying method. The developed scaffolds were characterized for their physicochemical, mechanical and in-vitro biological properties. In addition, the effect of AC on the attachment, proliferation and differentiation of osteoblast MG 63 cells was evaluated by scanning electron microscopy (SEM), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, alkaline phosphatase (ALP) activity assay and alizarin red stain-based (ARS) assay. All the PVA-AC composite scaffolds exhibited good bioactivity, hemocompatibility and protein adsorption properties. The scaffolds with high AC concentration (2.5 wt%) showed controlled drug release kinetics that are suitable for long term healing. The mechanical properties of all the PVA-AC composite scaffolds were improved when compared to the pure PVA scaffold. The high porosity, swelling degree and hydrophilicity of PVA-AC composite scaffolds facilitated cell attachment and proliferation. This is due to porous AC present in the sample that supported the osteoblast differentiation and formed mineralized nodules without the addition of any extra agents. From the above studies, it can be concluded that PVA-AC composite scaffolds are promising biomaterials for bone tissue engineering applications.

ZnO/Zn/Amorphous Carbon Matrix Nanostructured Composite Powder: a New Photocatalyst for Dye

ABSTRACTBoth synthesis and photocatalytic potential of an innovative catalyst-powder type composite material based on the Zn or/and ZnO dispersed in a matrix of amorphous-carbon have been investigated. Zn/ZnO/amorphous-carbon nanostructured-matrix composite was prepared by partial pyrolysis method based on the Pechini method. The amorphous character of composite was characterized X-ray diffraction, while chemical bond investigated by infrared spectroscopy. The photocatalytic activity directed to the degradation of the phenol red dye of small fraction of commercial ZnO, Zn/C and Zn/ZnO/C composites were evaluated as a function of the degradation reaction of the phenol red dye, in the alkaline medium pH = 9. A mass concentration of 1:10,000 was selected being considered 30 and 150 min of reaction A comparison between photocatalytic activity showed that the degradation rate of phenol red dye is more efficient at both ZnO/Zn/C and Zn/C amorphous composites when compared to the pristine ZnO. The efficiency obeys the following order C/Zn ≥ C/ZnO/Zn > commercial ZnO with conversion equal to 70% for C/Zn and C/ZnO/Zn, while for the ZnO is around 55%. The kinetic of degradation is discussed.

Cellulose/inorganic-composite fibers for producing textile fabrics of high X-ray absorption properties

Common textile materials as cotton or polyester do not possess reliable X-ray absorption properties. This is due to their morphology and chemical composition in particular. Common fibers are built up from organic polymers containing mainly the elements carbon, hydrogen, oxygen and nitrogen. These “light” elements only have low X-ray absorption coefficients. In contrast, inorganic materials composed of “heavy” elements with high atomic numbers, e.g. barium or bismuth, exhibit X-ray absorption coefficients higher by up to two orders of magnitude. To obtain a flexible yarn with high X-ray absorption properties both these materials, the organic polymer and the inorganic X-ray absorber, are combined to an inorganic/organic composite fiber material. Hence, as the organic component cellulose from modified Lyocell-process is used as carrier fiber and blended with inorganic absorber particles of low toxicity and high absorption coefficients, as bariumsulphate, bariumtitanate or bismuthoxide. A content of inorganic absorber particles equally distributed in the whole fiber of up to 20% is achieved. The composite fibers are produced as staple or filament fibers and processed to multifilament or staple fiber yarns. The staple fiber yarns are rotor-spinned to increase the comfort of the subsequent textile material. Several woven fabrics, considering multilayer structure and different warp/weft density, are developed. The energy dependent X-ray shielding properties are determined in dependence on the different yarn compositions, yarn types and structural parameters of the woven fabrics. As a result, a production process of textile materials with comfortable and dedicated X-ray absorption properties is established. It offers a promising opportunity for manufacturing of specialized textiles, working clothes or uniforms applicable for medicine, air craft and security personal, mining as well as for innovative composite materials.

Micromechanical characterisation of Ni/Al hybrid foams by nano- and microindentation coupled with EBSD

Metal foams are a very interesting class of cellular materials that is often used for lightweight construction or as energy absorbers. Ni/Al hybrid metal foams are a new and innovative composite foam material, consisting of nano-nickel coated aluminium foams. Since the mechanical properties of foams are strongly related to their microstructure, in Ni/Al hybrid foams, the coating is an additional degree of freedom affecting the mechanical properties of the foams. For meaningful simulations of the material behaviour, a detailed knowledge of the material properties of both the coating and the aluminnium struts is necessary.In this study, the micromechanical material parameters of Ni/Al hybrid foams are evaluated by means of nanoindentation and microindentation of the Ni coating and the Al struts. The indentation methods were coupled with electron backscatter diffraction (EBSD) in order to combine the determined parameter with the local grain structure.

Pluronic/gelatin composites for controlled release of actives

This paper describes the preparation and the release properties of composite materials based on Pluronic F127 and gelatin hydrogels, which could be of interest in the field of enteral nutrition or drug administration. The composites were prepared by exploiting the opposite responsivity to temperature of a 20% w/w Pluronic F127 aqueous solution (critical gelation temperature around 23°C) and gelatin (gel–sol temperature transition around 30°C). Pluronic domains dispersed within a gelatin matrix were obtained by injecting cold Pluronic F127 solutions inside hot gelatin solutions, while homogenizing either with a magnetic stirrer or a high-energy mechanical disperser. Calorimetry indicates that the composites retain the individual gelling properties of Pluronic and gelatin. Different releasing properties were obtained as a function of the preparation protocol, the temperature and the pH. The release profiles have been studied by a Weibull analysis that clearly points out the dominating role of gelatin at 25°C. At 37°C the release accounts for a combined effect from both Pluronic F127 and gelatin, showing a more sustained profile with respect to gelatin hydrogels. This behavior, together with the ability of Pluronic F127 to upload both hydrophilic and hydrophobic drugs and flavors, makes these innovative composite materials very good candidates as FDA-approved carriers for enteral administration.

Ethanol adsorption onto carbonaceous and composite adsorbents for adsorptive cooling system

The aim of the present paper is the experimental characterization of adsorbent materials suitable for practical applications in adsorption refrigeration systems, employing ethanol as refrigerant. Different commercial activated carbons as well as a properly synthesized porous composite, composed of LiBr inside a silica gel host matrix, have been tested. A complete thermo-physical characterization, comprising nitrogen physi-sorption, specific heat and thermo-gravimetric equilibrium curves of ethanol adsorption over the sorbents, has been carried out. The equilibrium data have been fitted by means of the Dubinin – Astakhov equation.On the basis of the experimental data, a thermodynamic evaluation of the achievable performance of each adsorbent pair has been estimated by calculating the maximum COP (Coefficient of Performance) under typical working boundary conditions for refrigeration and air conditioning applications. The innovative composite material shows the highest thermodynamic performances of 0.64–0.72 for both tested working conditions. Nevertheless, the best carbonaceous material reaches COP value comparable with the synthesized composite.The results have demonstrated the potential of the chosen adsorbents for utilization in adsorption cooling systems.

Reliability and adaptability of the analytical models proposed for the FRP systems to the Steel Reinforced Polymer and Steel Reinforced Grout strengthening systems

The paper presents a theoretical prediction of the structural behavior of reinforced concrete (RC) beams externally strengthened to flexure by using a unidirectional ultra-high tensile strength steel (UHTSS) reinforcing mesh embedded in an inorganic matrix (Steel Reinforced Grout, SRG) or in an organic matrix (Steel Reinforced Polymer, SRP).For these innovative composite materials are not yet available in literature specific standard documents, guidelines or analytical models capable to predict the structural behavior of the strengthened elements. Therefore, in order to evaluate the flexural strength of the strengthened beams some analytical models to predict the maximum axial strain developed in Fiber Reinforced Polymer (FRP) systems at the onset of intermediate debonding failure, have been used.The goal is to assess the effectiveness of current analytical models used, up to day, to FRP strengthening systems to the SRG and SRP strengthening systems. For this aim, a database of experimental results on RC beams strengthened in bending by bonded SRG and SRP systems has been collected.The comparisons between the theoretical predictions and the experimental data, in terms of debonding strain values, load carrying capacity, load-midspan deflection curves, have highlighted the reliability and adaptability of the current analytical models.Finally, in order to evaluate the effectiveness of the SRG and SRP systems for strengthening RC beams a parametric study was also carried out.

Thin‐walled shell structures made of textile‐reinforced concrete

AbstractAt RWTH Aachen University recently, a pavilion was constructed with a roof shell made of textile‐reinforced concrete (TRC), a composite material consisting of a fine‐grained concrete and high‐strength, non‐corroding textile reinforcement in the form of carbon fibres. The thin‐walled TRC shell structure demonstrates impressively the loadbearing capacity of this innovative composite material. The present paper discusses the practical issues concerning the construction, such as the fabrication of the TRC shells using shotcrete, the concepts developed for the arrangement of the textile reinforcement and the erection of the shells on top of the precast concrete columns. The issues concerning the design, assessment and numerical simulation of the loadbearing behaviour of TRC shells are presented in the companion paper (Part II).

Evaluation of the performance of recycled textile fibres in the mechanical behaviour of a gypsum and cork composite material

Given the need for using more sustainable constructive solutions, an innovative composite material based on a combination of distinct industrial by-products is proposed aiming to reduce waste and energy consumption in the production of construction materials. The raw materials are thermal activated flue-gas desulphurization (FGD) gypsum, which acts as a binder, granulated cork as the aggregate and recycled textile fibres from used tyres intended to reinforce the material.This paper presents the results of the design of the composite mortar mixes, the characterization of the key physical properties (density, porosity and ultrasonic pulse velocity) and the mechanical validation based on uniaxial compressive tests and fracture energy tests. In the experimental campaign, the influence of the percentage of the raw materials in terms of gypsum mass, on the mechanical properties of the composite material was assessed.It was observed that the percentage of granulated cork decreases the compressive strength of the composite material but contributes to the increase in the compressive fracture energy. Besides, the recycled textile fibres play an important role in the mode I fracture process and in the fracture energy of the composite material, resulting in a considerable increase in the mode I fracture energy.

3D Printing of Fractal Deterministic Shapes into Polymer Matrix with Respect to Final Composite Mechanical Properties

This paper deals with mechanical properties research of innovative polymer multiphase composite materials consisting of matrix and isotropic or anisotropic oriented deterministic fractal shapes made by 3D printing. Standard polymer composite materials consisting for example of polypropylene matrix and glass fibres have mechanical properties which depend mainly on matrix-fibre interface strength, fibre length, fibre strength and fibres orientation. [1] In case of under critical fibre length is fibres orientation stochastic in for example injection moulded composites. So is possible to say that mechanical properties of these (standard) composites with short fibres are isotropic and thus all direction limited. However by creating of reinforcing internal structure consisting of deterministic fractal connected shapes is possible to gain unlimited mechanical properties directing. These fractal shapes – placed in multiphase system matrix – are significantly influencing whole material system mechanical properties mainly in case of stress on the limit of strength, proportional elongation on the limit of strength or tensile/ flexural modulus. Fractal shapes are also possible to properly locate, orient or shape modify according to potential material using with goal to gain maximal efficiency of fractal shapes occurrence. Producing of this multiphase system is realized by the help of two component 3D printing technology. So is possible to create any fractal shapes placed in polymer matrix which are by another technology unmanufacturable. Mechanical properties analyse is performed with respect to fractal shape type, fractal dimension, fractal shape orientation and shear and tensile strength of matrix.