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Background There is a lack of reliable methods to obtain valid measurements of the tensile response of high performance materials such as fibre composites, ceramics and textile products at high rates of strain. Objective We propose and assess two new test techniques aimed at measuring valid tensile stress versus strain curves at high and ultra-high strain rates. Methods We conduct detailed, non-linear explicit Finite Element (FE) simulations of the transient response of the test apparatus and specimen during the tests and we develop simple analytical models to interpret the test measurements. We consider two test techniques: one based on the split Hopkinson bar apparatus, and suitable for strain rates of up to 1000 /s, and a second technique relying on projectile impact and aimed at measurements at strain rates higher than 1000 /s. Results The simulations are successfully validated using test data at strain rates of order 200 /s and then used to predict the test performance at strain rates up to approximately 5500 /s. We find that both techniques can give valid stress versus strain curves across a wide range of strain rates. Conclusions We identify the limits of both techniques and recommend optimal measurement strategies for dynamic testing of materials with different ductility.

Novel bioeconomic approaches call for increasingly faster production of lignocellulosic biomass and its bettertailored use for higher added value. The high-yield capacity and structural properties of willows (Salix spp.) suggest their excellent potential for the production of designed biochar for use in agronomic, electronic and technical applications. All these applications rely on the internal pore structure of biochar. However, we lack an in-depth quantitative understanding of the interlinkages between the feedstock properties and the physical quality of the biochar produced. We studied quantitatively how the clonal and within-plant properties of five different willow clones (hybrids of Salix schwerinii E.L. Wolf) affected the micrometre-scale pore properties of the produced biochars (pyrolyzed at + 462 ?C). The porosity and pore size distribution were analysed before and after slow pyrolysis by X-ray microtomography and image analysis. We also studied the potential of conventional low-cost fibre analysis techniques to be used to predict biochar pore properties directly from fresh feedstock. The total porosity (0.55?0.62) and the pore size distribution of willow wood and derived biochars varied between clones. Approximately two-thirds of the biochar total porosity was associated with pores formed by wood fibres. Pyrolysis levelled off the structural variation detected between and within the clones. Pyrolysis-induced shrinkage reduced the pore sizes and narrowed the pore size distribution. The results suggest that conventional fibre analysis techniques could be utilized to predict biochar homogeneity. Short rotation coppice willows are suitable feedstock to produce homogenous biochar precursor for production of bio-based carbon materials to be used in high value-added technical applications. The structural homogeneity of the feedstock and produced biochar can be enhanced by selecting proper harvesting strategy and clones used in plantations. From the industrial perspective, comprehensive understanding of feedstock properties helps to control quality of the produced biochar.

As a promising organic semiconducting material, polymeric graphitic carbon nitride (g-C3N4) has attracted much attention due to its excellent optical and photoelectrochemical properties, thermal stability, chemical inertness, nontoxicity, abundance, and low cost. Its advantageous visible light-induced photocatalytic activity has already been beneficially used in the fields of environmental remediation, biological applications, healthcare, energy conversion and storage, and fuel production. Despite the recognized potential of g-C3N4, there is still a knowledge gap in the application of g-C3N4 in the field of textiles, with no published reviews on the g-C3N4-functionalization of textile materials. Therefore, this review article aims to provide a critical overview of recent advances in the surface and bulk modification of textile fibres by g-C3N4 and its composites to tailor photocatalytic self-cleaning, antibacterial, and flame retardant properties as well as to create a textile catalytic platform for water disinfection, the removal of various organic pollutants from water, and selective organic transformations. This paper highlights the possibilities of producing g-C3N4-functionalized textile substrates and suggests some future prospects for this research area.

Large data sets of fibre mechanical properties were acquired using automated single fibre tensile testing equipment to improve the reliability of the measurements on T700S, 34-700, T300, HS40 and HYBON 2026 fibres. Although with the same nominal strength and stiffness, the T700S and 34-700 showed different Weibull modulus. A high number (over ~ 200) of the tests is necessary for accurate determination of the fibre strength Weibull parameters; samplings of ~ 50 tests can lead to a Weibull modulus deviation of ±1. Carbon fibre stiffening rate was shown to depend on the fibre type, contrary to previous reported observations. The stiffness of E-glass fibre, however, decreased with the applied strain. The non-linearity of the fibre stress-strain diagrams implies that the necessary compliance calibration should be done iteratively.

This data article presents fibre mechanical properties acquired using automated single fibre tensile testing equipment. The raw data consists of the fibre diameter, gauge length and load-displacement diagrams. A total of 690 fibres were tested across four carbon and one glass fibre type. The largest dataset, for the T700S carbon fibre, consists of 217 data points. After performing a compliance calibration, the load-displacement diagrams are converted into stress-strain diagrams from which the tensile modulus and strength are extracted. The data presented in this article can be used as input data for models or for data processing during determination of other properties experimentally. The interpretation of the data can be found in [1] . The data is hosted in the Mendeley Data repository at [2] .

This study evaluates the influence of moisture sorption on the properties of flax fibres and their composites. The radial swelling of both the elementary and technical flax fibres at a wide range of relative humidity (RH) values is determined. Moreover, the effects of moisture sorption on both the thickness swelling and flexural properties of flax/polyester and flax/epoxy composites are evaluated. Park's model is used to define the fibre moisture sorption curve. The model suggests that the moisture is first sorbed on hydrophilic fibre surfaces or microcavities until specific sites within the fibre reach saturation and later, the moisture forms aggregates at high RH. Flax elementary fibres have a lower radial swelling coefficient when compared to technical fibres, with radial swelling coefficients of βr = 1.2 and 1.9, respectively. At the composite level, flax/polyester and flax/epoxy systems have approximately the same thickness swelling coefficients, βt = 0.5 and 0.6, respectively, over the RH range, 11–97%. This behaviour could be explained by the constraining effect of the resins on flax fibres due to higher stiffness of matrix and probably due to resin penetrating the fibre lumen. Flexural properties of longitudinal and transverse fibre-oriented flax/polyester and flax/epoxy composites conditioned at different RH, and tested in fully dry condition, decreased as RH increased beyond 54%, likely due to moisture swelling which induced damage. This study provides new insights into the moisture sorption and dimensional changes of both the elementary and technical flax fibres and their composites and also the effects of moisture on the flexural properties of the composites.

Blended fibres are being utilized in ordinary Portland cement-based materials (CBMs). The inclusion of blended fibre (a mix of several fibre types) may help CBMs perform better under fire. Fibre factor (F.F) and mechanical characteristics of blended fibre-reinforced CBMs are investigated in this research under various temperature conditions. In addition to mechanical characteristics, empirical models for strength properties in response to temperature and F.F. are established. The addition of calcite powder to blended fibres in CBMs increased mechanical strength across the board at all temperatures. However, increasing the temperature from 20 °C to 750 °C resulted in 75%, 79%, and 84% reductions in compression, split tension, and flexure strength of blended fibre-reinforced CBMs, respectively. For compression, split tension, and flexure strength, empirical models with R2 values of 0.98, 0.92, and 0.93 were constructed, with fibre factor and temperature as the major affecting variables. Experimental data for blended fibre-reinforced CBMs revealed that empirical models predicted superior outcomes, which was brought into existence.

Thin plates made of Ultra-High-Performance Steel-Fibre-Reinforced Concrete (UHPSFRC) with textile Aramid fabrics were subjected to a projectile impact and its post-test damage was discussed. The damage degrees were the type of the response and crater surface, which was determined by using a 3D scanner. The most common type of ammunition, which is a 7.62 × 39mm calibre with a full-metal jacket and a mild-steel core, was used for all specimens. It was verified experimentally that the UHP-SFRC with textile Aramid fabrics has a better ballistic performance in comparison with its counterpart made of the UHP-SFRC without any textile reinforcement. Also, it was verified that specimens with the point or segment interconnection threads between the front side textile fabrics and rear side textile fabrics have a higher resistance due to the better integrity of the monolithic UHP-SFRC mixture.

Filament-wound composite tubular structures are frequently used in transmission systems, pressure vessels, and sports equipment. In this study, the failure mechanism of composite tubes reinforced with different fibres under low-velocity impact (LVI) and the radial residual compression performance of the impacted composite tubes were investigated. Four fibres, including carbon fiber-T800, carbon fiber-T700, basalt fibre, and glass fibre, were used to fabricate the composite tubes by the winding process. The internal matrix/fibre interface of the composite tubes before the LVI and their failure mechanism after the LVI were investigated by scanning electric microscopy and X-ray micro-computed tomography, respectively. The results showed that the composite tubes mainly fractured through the delamination and fibre breakage damage under the impact of 15 J energy. Delamination and localized fibre breakage occur in the glass fibre-reinforced composite (GFRP) and basalt fibre-reinforced composite (BFRP) tubes when subjected to LVI. While fibre breakage damage occurs globally in the carbon fibre-reinforced composite (CFRP) tubes. The GFRP tube showed the best impact resistance among all the tubes investigated. The basalt fibre-reinforced composite (BFRP) tube exhibited the lowest structural impact resistance. The impact resistance of the CFRP-T700 and CFRP-T800 tube differed slightly. The radial residual compression strength (R-RCS) of the BFRP tube is not sensitive to the impact, while that of the GFRP tube is shown to be highly sensitive to the impact.

In Selective Laser Sintering, fibres are strongly orientated during the powder recoating process. This effect leads to an additional increase of anisotropy in the final printed parts. This study investigates the influence of process parameter variation on the mechanical properties and the fibre orientation. A full factorial design of experiment was created to evaluate the processing parameters of recoating speed, layer thickness and laser power on the part’s modulus of elasticity. Based on the mechanical testing, computed tomography was applied to selected samples to investigate the process-induced fibre microstructure, and calculate the fibre orientation tensors. The results show increasing part stiffness in the deposition direction, with decreasing layer thickness and increasing laser power, while the recoating speed only shows little effect on the mechanical performance. This complies with computed tomography imaging results, which show an increase in fibre orientation with smaller layer thickness. With thinner layers, and hence smaller shear gaps, shear stresses induced by the roller during recoating increase significantly, leading to excessive fibre reorientation and alignment. The high level of fibre alignment implies an increase of strength and stiffness in the recoating direction. In addition, thinner layer thickness under constant laser energy density results in improved melting behaviour, and thus improved fibre consolidation, consequently further increasing the mechanical properties. Meanwhile, the parameters of recoating speed and laser power do not have a significant impact on fibre orientation within their applicable process windows.

The aim of this paper is to evaluate the influence of sustainable surface treatments —performed on flax nonwoven fabrics as textile reinforcement— on the durability of calcium aluminate cement (CAC) based composites. Two treatments are considered: an alkaline treatment (for increased stability and adhesion), and a treatment with soybean oil (to reduce fiber degradation). The cement hydration was studied by analysis of back-scattered scanning electron microscopy images, which revealed variations nearby the fibers owing their capacity for water absorption and presence of oil on the surface. A retarding effect on cement hydration was observed on the composites prepared with the oil-treated fabrics. The composites containing the alkali treated fabrics had better mechanical properties and also the highest durability. For these composites it was found an optimized fiber-matrix adhesion and penetrability of the cement to the fabric.

Computational fluid dynamics (CFD) was used to investigate characteristics of high-speed air as it is expelled from a solution blow spinning (SBS) nozzle using a k-&epsilon, turbulence model. Air velocity, pressure, temperature, turbulent kinetic energy and density contours were generated and analysed in order to achieve an optimal attenuation force for fibre production. A bespoke convergent nozzle was used to produce polyvinylidene fluoride (PVDF) fibres at air pressures between 1 and 5 bar. The nozzle comprised of four parts: a polymer solution syringe holder, an air inlet, an air chamber, and a cap that covers the air chamber. A custom-built SBS setup was used to produce PVDF submicron fibres which were consequently analysed using scanning electron microscope (SEM) for their morphological features. Both theoretical and experimental observations showed that a higher air pressure (4 bar) is more suitable to achieve thin fibres of PVDF. However, fibre diameter increased at 5 bar and intertwined ropes of fibres were also observed.

Nopal is a potential source of mucilage that can be used in different food applications. One of its potential use is the development of films and coatings where it can act as a packaging material but also as a source of bioactive compounds. Therefore, this work aimed to develop and characterize pectin-based films loaded with mucilage extracted from two species of nopal, Copena F1 (Cop) and Villanueva (Vi). The obtained mucilages were denominated as materials without fibre (Copwtf and Viwtf) and with fibre (Copwf and Viwf), according to the fibre&rsquo, s size. Films were produced with pectin (2% w/v), mucilage (2.5% w/v) and glycerol (0.5% w/v) by the casting method. The addition of mucilages was shown to influence the visual appearance, optical properties and morphology of the films. The presence of mucilage also changed the moisture content, water contact angle and water vapour permeability of the films. The pectin-based films without mucilage presented the best mechanical properties. Fourier-transform infrared (FTIR) spectroscopy showed similar signals in terms of frequency and intensity, for all the films, not showing any chemical modification. Results show that the mucilage obtained from different nopal fractions can be used in pectin-based films foreseeing their use as films or coatings in food applications.

In this study, differences in the kinetics of the thermal-supported hydrolytic degradation of polylactide (PLA) wet spinning fibres due to material variance in the initial molecular and supramolecular structure were analysed. The investigation was carried out at the microstructural and molecular levels by using readily available methods such as scanning electron microscopy, mass erosion measurement and estimation of intrinsic viscosity. The results show a varying degree of influence of the initial structure on the degradation rate of the studied PLA fibres. The experiment shows that hydrolytic degradation at a temperature close to the cold crystallization temperature is, on a macroscopic level, definitely more rapid for the amorphous material, while on a molecular scale it is similar to a semi-crystalline material. Furthermore, for the adopted degradation temperature of 90 &deg, C, a marginal influence of the pH of the degradation medium on the degradation kinetics was also demonstrated.

Wood-wood cement boards (WWCB) have been extensively used as ceiling tiles or insulating walls thanks to their good thermal and acoustic properties. Nowadays, the trend is to use sustainable materials like waste fibres. These waste fibres are widely available at a low cost and despite their good properties, are usually landfilled or incinerated. Among them, coir fibres, extracted from the husk of the coconut, are a good candidate to replace conventional fibres in composite materials. However, preliminary results have shown that despite their good physical properties and great cement compatibility, coir fibres cement boards have poor mechanical performances. This is mainly due to the poor interface between the cement and the fibre, leading to a very week fibre/matrix load transfer. The objective of the present study is to produce coir fibres cement boards having the required mechanical properties in order to be used as insulated interior wall or ceiling panels. First, the interfacial properties between the fibres and the cement will be investigated and improved by modifying the surface of the fibres thanks to chemical pre-treatments. Then, the process and design of cement boards will be studied in order to optimize the process, improving the overall properties of the boards. Finally, the mechanical and physical properties of these boards will be measured and compared to conventional WWCB.

The expression waste-to-energy technologies is increasingly being used regarding waste reduction and utilization. Waste-to-energy technologies are procedures used to generate different forms of energy starting from a waste source. Considering that this pap waste, the previously mentioned procedures can be divided into mechanical, thermal and chemical treatment of composite waste. Thermal treatment processes provide a wide range of options to produce electricity, heat, oils, gases, fuels and chemicals starting waste. Some procedures are used for commercial purposes, while many are still being developed in laboratories or semi-industrial plants. The presented paper is focused to briefly review recent ld of thermal treatment of composite waste materials. Proizvodnja energije iz otpadnih materijala primenom različitih tehnologija je jedan od načina ponovne upotrebe i ujedno redukcije otpadnih materijala. Sve ove tehnologije reciklaže imaju jednu zajedničku karakteristiku - dobijanje energije u različitim oblicima, polazeci od otpadnih materijala kao sirovina. Imajuci u vidu da je ovaj rad fokusiran na kompozitne otpadne materijale, pomenute procedure se mogu podeliti na mehaničke, termičke i hemijske tretmane kompozithog otpada. Termički tretmanima kompozitnog otpada je moguća proizvodnja energije u vidu eliktriciteta, toplote, ulja, gasova, goriva i različitih hemijskih jedinjenja. Pojedine procedure su uvedene u komercijalnu upotrebu, dok se veliki broj njih trenutno razvija u laboratorijskim ili poluindustrijskim postrojenjima. U radu je ukratko dat prikaz trenutnog stanja i inovacija u oblasti termičkog tretmana otpadnih kompozitnih materijala.

In this study, the back calculated compressive properties of flax fibers utilizing the Impregnated Fiber Bundle Test (IFBT) were investigated. The back calculated stress-strain response can be described by the Ramberg-Osgood model. The compressive modulus of the fiber is similar to its tensile modulus. The compressive strength of the fiber is approximately 45 % of its tensile strength. Considering the presence of local fiber kinking within the elementary fibers as well as global fiber kinking due to fiber misalignments and plastic shear deformation in the matrix material, this is a remarkably high value for the compressive strength. Our results indicate that local fiber kinking precedes global fiber kinking. We show that IFBT is a promising method for determining the compressive properties of flax fibers and provides necessary input data for finite element analysis of the compressive failure mechanisms in unidirectional flax fiber reinforced composites. QC 20220215

Two different commercial bleaching products containing hypochlorite were used on different fabrics (plain-weave cotton, knitted cotton, plain-weave polyester-cotton and knitted lycra-cotton) to verify possible fibres damages. Bleaching products differ each other for the alkaline formulation. In particular, one of them has an alkaline bleaching formulation and the other has a low-alkaline bleaching formulation. The degree of whiteness, the tensile and bursting strength, and the thermal and surface properties were evaluated after a different number of washing cycles. The obtained results reveal that the alkaline bleaching product is better than the low-alkaline bleaching product in maintaining mechanical properties and in improving optical properties of the fabrics.

The hybrid configuration of bio-reinforced composites has established a new extended boundary for the development of pro-ecological technologies due to light weight, moderate specific strength, low cost, environmental benefits, and potential applications of natural components. This work investigates the physical and mechanical properties of hybrid composites made of sisal/glass fibres and Portland cement inclusions. A full factorial design was generated to identify the effects of the stacking sequence and cement particles on the flexural strength, flexural stiffness, apparent density, apparent porosity and water absorption of the composites. The significant contributions of these main factors and their interactions were determined via Design of Experiments (DoE) and Analysis of Variance (ANOVA). The fracture features and damage mechanisms of hybrid composite were also reported. The inclusion of cement microparticles led to an increased apparent porosity, as well as enhanced water absorption, flexural stiffness and flexural strength of the hybrid composites. The mechanical properties were strongly dependent on the fibre stacking sequence, which accounts for approximately 98% of the effects observed. Moreover, the stacking sequence affected the damage mechanism of the bio-composites. Finally, the replacement of glass fibres by unidirectional sisal reinforcements may potentially improve the specific properties in structural applications with an environmental sustainable footprint.

[EN] Traditionally, glass fibre has been used as plastic reinforcement whenever mechanical properties of a matrix, like stiffness, do not meet the specifications. However, current tendencies try to replace glass fibres by more sustainable fibres to obtain eco-friendlier products. Natural fibres show comparatively good physical and mechanical properties and, unlike glass fibres, come from renewable resources and are recyclable and sustainable. In this work, hemp straw discarded from hemp manufacturing was used as reinforcement in polypropylene composites. One drawback associated to hemp straw is its high lignin content that reduces its reinforcing potential. Therefore, a soft alkaline treatment was employed to adjust the lignin contents. In this work, the evolution of the Young's modulus with the NaOH treatment is assessed and discussed. Intrinsic Young's moduli of hemp straw fibres at different alkaline conditions were determined by Hirsch model. Finally, Tsai-Pagano and Halpin-Tsai equations allowed the prediction of the theoretical Young's modulus of the composites. The results showed the competitiveness of a by-product reinforced composite in front of commodity materials.

The SHS technique was experimented in chrysotile breakdown. By means of two reactions such as Mg 3 Si 2 O 5 (OH) 4 + Fe 2 O 3 + 3 Mg and 2Mg 3 Si 2 O 5 (OH) 4 + Fe 3 O 4 + 4 Mg the chrysotile was completely converted into forsterite-rich olivine. Different mixtures of hematite + Mg and magnetite + Mg were tested with chrysotile to establish the maximum chrysotile amount in order to allow the reaction. In comparison with conventional thermal treatments, the SHS process is characterized by a fast reaction, needs low activation energy and the apparatus is simple. For these reasons, the asbestos neutralisation is carried out with positive balance of time and costs of the process. Furthermore, the combustion product can be re-used as secondary material.

The use of Natural Fibers in cementitious composites is an innovative technical solution but, they are characterized by a complex microstructure and significant heterogeneity, which influence their interaction with cementitious matrices, whose identification requires further advances in the current state of knowledge. The present study summarizes the results of a wide series of pull-out tests carried out on sisal, curaua and jute fibers. Then, the experimental results are employed in an inverse identification procedure aimed at unveiling the key features of the aforementioned bond-slip laws. Morphological, chemical, physical and mechanical characterization of the natural fibers were correlated with the resulting bond properties within the embedding matrix. The obtained results in terms of relevant parameters, such as bond strength and fracture energy (under pull-out stresses) of the fiber-matrix interface, pave the way for future studies intended for a better understanding of the structural response of Natural Fiber Reinforced Cementitious Composites.

© 2018, © 2018 Institute of Materials, Minerals and Mining and ASM International Published by Taylor & Francis on behalf of the Institute and ASM International. Fibre-hybrid composites are composed of two or more fibre types in a matrix. Such composites offer more design freedom than non-hybrid composites. The aim is often to alleviate the drawbacks of one of the fibre types while keeping the benefits of the other. The hybridisation can also lead to synergetic effects or to properties that neither of the constituents possess. Even though fibre-hybrid composites are attractive, they also pose more challenges in terms of materials selection than conventional, single fibre type composites. This review analyses the mechanisms for synergetic effects provides guidance on the fibre and matrix selection and describes recent opportunities and trends. It finishes by describing the current applications, and by contrasting how the industrial use is different from the academic research. ispartof: INTERNATIONAL MATERIALS REVIEWS vol:64 issue:4 pages:181-215 status: published

This research focuses on designing and characterizing steel-fibre-reinforced self-compacting concrete using recycled aggregates (SFR-SCC-RA). Six different concrete dosages have been designed, and two extensive mechanical and physical characterization programs have been conducted. The first program was developed in a concrete production plant to verify the compatibility of the new material with the existing production systems. The second program was developed in a laboratory under controlled temperature and humidity conditions. Although compressive strengths greater than 25 N/mm2 have been reached (which allows the material to be classified as structural), the design in this initial phase is oriented to applications with limited mechanical requirements (e.g., foundations, earth retaining walls and pavements, in which design forces are moderate).

A new cement-based material is presented in this research contribution. The material consists in a fibre-reinforced self-compacting concrete with 100% of mixed recycled aggregate. Six different mixes were produced in two different conditions: (1) in a concrete plant in order to verify the adaptability of the existing equipment to produce and pour this material under real boundary conditions and (2) in laboratory controlled conditions. A physical (density, porosity, fibre distribution and orientation) and mechanical (compressive, tensile and post-cracking strengths, Young modulus) characterization involving 1,100 specimens was carried out. The results obtained permit to conclude that compressive concrete strength superior to 30 MPa can be achieved with certain ductility and tenacity. In based of these results, this material could be used in applications like foundations, ground-supported slabs, retaining systems and other elements with moderate structural responsibility.

Steel Mesh-Reinforced Cementitious Composites (SMRCC) (traditionally known as ferrocement) have been in existence for few decades, but have some limitations set on element thickness and number of reinforcing mesh layers and the resulting deflection ductility. Therefore, the author has made an attempt to explore whether deflection ductility will improve in mesh-reinforced cementitious composites (25 mm thick) if discontinuous fibres are added to slab elements. For this purpose, thin slab elements of dimensions 700 mm (length) × 200 mm (width) × 25 mm (thickness) were cast and subjected to four point bending tests. Based on the flexural tests conducted on SMRCC (Control Slab Elements, cast with Steel Mesh Volume of reinforcement, MVr=0.78, 0.94, and 1.23%) and Hybrid Mesh-and-Fibre-Reinforced Cement Based Composite (HMFRCBC) (Test Slab Elements, combining MVr=0.78, 0.94 and 1.23% and Polyolefin Fibre Volume fraction, PO-FVf=0.5-2.5% of volume of specimens, with 0.5% interval), load-deflection and the deflection ductility index were analyzed. From the flexural load-deflection curves it has been observed that HMFRCBC slabs demonstrate higher flexural load-carrying capacity and deflection ductility when compared to SMRCC slabs. This study shows that higher the polyolefin fibre volume fraction (PO-FVr) from 0.5 to 2.5% (with a 0.5% interval) in HMFRCBC slabs, the higher the flexural deflection ductility. The Deflection Ductility Index (DDI) of HMFRCBC (with 5 layers of mesh and PO-FVr=2.5%) is 4.5 times that of SMRCC. This study recommends that HMFRCBC can be used as an innovative construction material due to its higher flexural ductility characteristics.

The complex structure of the annulus fibrosus is strongly related to its mechanical properties. Recent work showed that it is possible to observe the relative movement of fibre bundles in loaded cow tail annulus; the aim of this work was to describe and quantify annulus fibrosus micromechanics in degenerated human disc, and compare it with cow tail annulus, an animal model often used in the literature. Second harmonic generation was used to image the collagen matrix in twenty strips of annulus fibrosus harvested from intervertebral disc of seven patients undergoing surgery. Samples were loaded to 6% tensile strain in 1% steps. Elastic modulus was calculated from loading curves, and micromechanical strains were calculated from the images using custom software. The same protocol was applied to twenty strips of annulus harvested from cow tail discs. Significant morphological differences were found between human and cow tail samples, the most striking being the lack of collagen fibre crimp in the former. Fibres were also observed bending and running from one lamella to the other, forming a strong flexible interface. Interdigitation of fibre bundles was also present at this interface. Quantitative results show complex patterns of inter-bundle and inter-lamellar behaviour, with inter-bundle sliding being the main strain mechanism. Elastic modulus was similar between species, and it was not affected by the degree of degeneration. This work gives an insight into the complex structure and mechanical function of the annulus fibrosus, which should be accounted for in disc numerical modelling. Electronic supplementary material The online version of this article (doi:10.1007/s10237-017-0900-z) contains supplementary material, which is available to authorized users.

This work shows the practical application and the experimental validation of a procedure based on an algorithm, running in a finite element environment, able to operate inside a convex three-dimensional solid by replacing the continuous mass with an appropriate cancellous bone-inspired space frame sharing, with the solid, the border and organized for having the fibres oriented according to the boundary conditions. The purpose is to reach the maximum mechanical efficiency realizing a load adaptive space frame optimized in terms of weight. Young's moduli of a cubic virtual specimen were numerically estimated. Fifteen specimens were printed by a 3D printer using a titanium alloy. Numerical results were compared with experimental ones obtained by tensile tests. The simulation results confirmed the validity of the FEM “beam element-based” space frame.

In most of cases, technological processing leads to microstructure anisotropy of material. Results obtained from the analysis of anisotropy can be used for evaluation of material properties and parameters of technology processes. Stereological metallography was used for describing of structure anisotropy. In case of plastically deformed material, degree of orientation of grain boundaries was determined. Grain boundaries are decomposed into isotropic, planar and linear oriented components - specific surface area of grain boundaries and these parameters were measured using oriented test lines stereology method. These results were used for estimation of local plastic deformation using conversion model of orientation grain boundaries to deformation of grains. Our proposed conversion method enables estimation of local plastic deformation in arbitrary place of body with arbitrary state of initial deformation. In case of short fibre reinforced thermoplastics oriented test plane stereology method was used for estimation of experimental orientation of fibres. Degree of orientation was estimated from the number of intersections of fibres with test planes and from these results components of an orientation tensor are estimated. This method is very simple in comparison with a current method which is based on measurement of dimensions and orientation of lot of fibre intersections in analyzed plane.

The introduction of Variable-Stiffness Laminates requires not only the use of advanced numerical simulation tools but also better understanding of manufacturing induced effects. These computational tools can give beneficial insight that will lead to an effective reduction of test campaigns as well as to increase design possibilities. This paper presents a virtual testing approach to study the influence of tow-drop effects, generated in the manufacturing of steered-fibre composites, by means of nonlinear finite element analyses within the framework of fracture and damage mechanics. X-ray computed tomography was used to characterise the embedded resin-rich areas. Both the progressive failure mechanisms and the ultimate failure loads can be predicted with high realism when compared with experimental observations. In addition, the differences of the tow-drop effects on plain and notched laminates can also be predicted accurately The authors acknowledge the financial support of the Ministerio de Economía y Competitividad of Spain under project MAT2009-07918. The first author would also like to thank the Generalitat de Catalunya for the FI pre-doctorate Grant 2010FI_B00658

Nanofibers of poly(vinyl alcohol) (PVA) reinforced with cellulose nanofibrils (CNFs) and/or crosslinked with maleic anhydride (MA) were produced by electrospinning technique to compare the additivation effects of the polymeric matrix. The results suggested that the PVA mass fraction equal to 14%, CNFs volumetric fraction of 3% and maleic acid at the molar ratio 20:1 are the best proportions for renewable base fibres production. In this study, the best electrospinning parameters for membranes production were obtained at the applied voltage of 24 kV, needle tip-to-collector distance of 14.5 cm, feed rate of 0.3 mL h1 and using a plate collector. CNFs and MA additions allow to improve nanofiber thermal properties and resistance to water degradation, which result in an eco-friendlier, biocompatible and long-term biodegradable nanofiber mats with diameters of 74±33 nm for water filtration purposes., The authors acknowledge the Portuguese Foundation for Science and Technology (FCT) for funding the project UID/CTM/00264/2013 and A. Zille contract IF/00071/2015., info:eu-repo/semantics/publishedVersion

Sized glass fibre bundles were treated using atmospheric pressure plasma in a helium/tetrafluoromethane gas mixture. X-ray photoelectron spectroscopy showed that fluorine was introduced onto the sizing surface. A new analysis method (dynamic micro-wetting) to determine the wetting rate of the plasma-treated fibre bundles is presented. The dynamic micro-wetting test using glycerol as a test liquid showed a reduced wetting rate after plasma treatment. It is demonstrated that dynamic micro-wetting is a useful tool for the characterization of fibre bundle wetting.

During the casting of steel fibre reinforced concrete (SFRC) the orientation of fibres is influenced by flow dynamics of concrete mass. A simple theoretical model presented allows the calculation of velocity gradient matrices for concrete mass based on steel fibre orientations measured in the hardened concrete samples taken from the different regions in the slabs. This made it possible to examine the realistic trends of the flow near the formwork or free surface or in the bulk material. Eigenvalues and eigenvectors of the matrices show the directions of the maximal and minimal velocity changes, which can be compared in different positions of the slabs. The outcomes of the study can contribute to controlled production technology of SFRC.

International audience; Living cells embedded in a complex Extra–Cellular Matrix (ECM) migrate in a sophisticated way thanks to adhesions to matrix fibres and contractility. It is important to know what kind of forces are exerted by the cells. Here we use reflectance confocal microscopy to locate fibres accurately and determine displacement fields. Correlation techniques are used to this aim, coupled with proper digital image processing. Benchmark tests validate the method in the case of shear and stretching motions. Finally, the method is tested successfully for studying cancer cells migrating in collagengels of different concentration.KEYWORDS: Displacement field, phase correlation, confocal microscopy, cell migration, fibres, cancer cells.

Glass fibres slowly degrade due to dissolution when exposed to water. Such environmental aging results in the deterioration of the mechanical properties. In structural offshore and marine applications, as well as in the wind energy sector, R-glass fibre composites are continuously exposed to water and humid environments for decades, with a typical design lifetime being around 25 years or more. During this lifetime, these materials are affected by various temperatures, acidity levels, and mechanical loads. A Dissolving Cylinder Zero-Order Kinetic (DCZOK) model was able to explain the long-term dissolution of R-glass fibres, considering the influence of the pH , temperature, and stress corrosion. The effects of these environmental conditions on the dissolution rate constants and activation energies of dissolution were obtained. Experimentally, dissolution was measured using High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS). For stress corrosion, a custom rig was designed and used. The temperature showed an Arrhenius-type influence on the kinetics, increasing the rate of dissolution exponentially with increasing temperature. In comparison with neutral conditions, basic and acidic aqueous environments showed an increase in the dissolution rates, affecting the lifetime of glass fibres negatively. External loads also increased glass dissolution rates due to stress corrosion. The model was able to capture all of these effect © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Acknowledgements: The authors are grateful to FEDER – Fundo Europeu de Desenvolvimento Regional, in the aim of COMPETE 2020 with the copromotional project WOWW - World of Outstanding Wool and Wood and to Portuguese Foundation for Science and Technology (FCT) through the Project reference UID/Multi/04044/2013 and PAMI – ROTEIRO/0328/2013 (Nº 022158). The authors gratefully acknowledge the contribution to language revision of Dr Sonia Fiuza. The Coimbra Chemistry Centre, CQC, supported by FCT, through the project PEstOE/QUI/UI0313/2013 is also acknowledged In the last decades the studies on thermoplastic composites reinforced with natural fibres have been mostly focused on vegetable lignocellulosic or cellulosic fibres. These materials provide eco-sustainable solutions for a large range of applications and have been actually adopted by multiple industries. The interest on fibres of animal origin is more recent and research on composites reinforced with these fibres predominantly composed of keratin, such as wool, feathers or silk, is increasing in virtue of some advantageous properties that may overcome some of the intrinsic limitations from vegetable fibres. The combined use of vegetable and animal fibres in composites appropriate for melt blending processing is at early stages of research. After chemical treatments, the fibres of animal origin have been mostly applied as binders between vegetable fibres and polymers, but not as main constituents of these composites. The use of both types of fibres simultaneously in composites of thermoplastic matrices is the subject of the present study where the fibres of animal origin (wool) are sourced from different kinds of residues from a textile industry and the fibres of vegetable origin (wood) are the residues from carpentry activities. The chemical composition, the macro and microstructure of the fibres is analyzed, as well as that of the composites that combine non-biodegradable and biodegradable polymers with diverse ratios of the fibres in different conditions (wool as cards, yarns and felt cloths; wood as sawdust). The addition of coupling agents to enhance the compatibility between wool, wood and different polymers is also analysed. info:eu-repo/semantics/publishedVersion

This chapter deals with protein nanofibrils (PNFs), also referred to as amyloid fibrils. This is an emerging field in nanoscience and engineering. Sources for PNFs, ways of making these, including the mechanisms of the fibrillation process, and factors affecting the production process are presented here. Properties of the PNFs themselves as well as properties and preparation of PNF materials in the form of hydrogels, films, and fibres are also described. In this chapter, PNF-based nanocomposites and templates are also considered. Possible applications of PNFs are discussed and put in the perspective of future uses as, or in, industrial nanomaterials. Part of book ISBN 978-0-12-815749-7QC 20210901

International audience; Ceramic matrix composite (CMC) materials have been considered a desired solution for lightweight and high-temperature applications. Simultaneously, among all different CMC reinforcements, polymer-derived ceramic (PDC) fibres have gained attention for the intrinsic thermal stability and mechanical strength with simple and cost-effective synthesis techniques. Here, carbon-rich SiOCN fibres were synthesized via hand-drawing and polymer pyrolysis of a hybrid precursor of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasilazane (TTCSZ) and poly-acrylic acid (PAA). The type of silazane reported in this work is considered as a major precursor for SiCN; however, it is unspinnable, due to its unfavourable physical properties (low viscosity) and chemical structure (cyclic rather than linear structure). The introduction of PAA to TTCSZ to create a hybrid precursor remarkably improved the spinnability of the silazane and should be widely applicable to other unspinnable PDC pre-ceramic polymers. Investigations on the structural and compositional development of the fibres were mainly conducted via Raman spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance and thermo-gravimetric analysis to determine spinnability, free carbon content, cross-linking and pyrolysis behaviour of the fibres, respectively.

Anterior Cruciate Ligament (ACL) is one of the main ligaments within the knee. ACL is a dense fibrous tissue, its nonlinear stress-strain behaviour is related to fibres uncrimping, reorienting and tensioning, which inherently define its functional properties. Aim of this study was to design a setup able to acquire the 3D fibrous microstructure of ACL samples evolving under strain. A specific tensioning device – consisting in two clamps to hold the sample, a linear guide moved by a threaded rod for sample elongation, a load cell to measure reaction force and an aluminum frame – was designed to be inserted into the chamber of a high resolution micro-CT system (Skyscan 1176). Once clamped, ACL underwent 1, 2, 3, 4, 6 and 8% of elongation to reveal toe and linear region of the stress-strain curve. At each specific strain, specimen was scanned with a nominal resolution of 9 μm to non-destructively obtain 3D microstructure. Before testing, collagen fibres were highlighted by an optimized contrasting protocol which included the staining of ACL in a solution of 2% PTA in H2O. With the specific contrasting procedure and micro-CT resolution, it was possible to show the effect of strain variation on the different fibres bundles. Presented procedure makes it possible to obtain fundamental information about mechanical and microstructural characteristics, simultaneously addressing clinical and engineering issues related to ACL reconstruction. Current work is related to micro-CT image processing, in order to perform a 3D morphometric analysis on the fibres bundle changes in relation to their mechanical behaviour.

The ferrierite crystal structure has often been subject to discussion because of the possible lowering of symmetry from the space group Immm. It mainly occurs in nature with a fibrous crystal habit, and because of the existence of line/planar defects in the framework, texture and preferred orientation effects it has been difficult to obtain an exact crystallographic model based only on the results from powder diffraction data. Therefore, nano-single-crystal diffraction and tomography data have been combined in order to improve the refinement with a meaningful model. High-quality single-crystal data, providing reliable structural information, and tomography images have been used as input for a Rietveld refinement which took into account a phenomenological description of stacking disorder and the analytical description of the preferred orientation, by means of spherical harmonics for strong texture effects. This is one of the first examples of application of synchrotron nano-diffraction for the structure solution of fibrous minerals of micrometre to nanometre size. The high quality of the crystals allowed collection of single-crystal X-ray diffraction data of up to 0.6 Å resolution, leading to an unambiguous solution and precise anisotropic refinement. Nano-single-crystal diffraction and phase contrast tomography data were collected at ID11 and the high-resolution powder diffraction patterns at ID22 of the European Synchrotron Radiation Facility. This detailed crystallographic characterization provides a basis for understanding the potential of ferrierite for toxicity and carcinogenicity.

A variety of applications, spanning from structural or biomedical engineering to flexible electronics, require the development of materials able to withstand high load and, at the same time, accommodate high strain before failure. While strength and toughness are often self-excluding properties in man-made materials, they can be efficiently combined by nature, which provides source of inspiration for novel materials design. Herein this paper, we pursue a bio-inspired approach, based on the introduction of a mechanical sink, such as a running knot, to improve the toughness modulus of high-performance polymeric microfibres. These are then enriched with additional smart features, such as a viscoelastic coating, surface roughening or a combination of those, to amplify the beneficial effect of the knot introduction. The role played by all such features on the mechanical performances of the prepared fibre samples, namely load at failure and toughness modulus increase, is then evaluated through a statistical technique, known as correspondence analysis (CA). While this exploratory analysis is widely adopted in biology, ecology, neuroscience or genetics, applications in structural or mechanical engineering are still rare. Here, we show that CA can be a powerful tool for the design of materials provided with enhanced toughness without losing strength.