High Fiber Fractions Research Articles

Evaluation of orthotropic elasticity of gradient-structured bamboo by microtensile testing combined with digital image correlation technique

Bamboo, a biomaterial with a unique gradient structure, possesses exceptional mechanical properties. The gradient structure impacts the mechanical properties of bamboo in the longitudinal (L), radial (R) and tangential (T) directions. To investigate the elasticity associated with gradient structure, we derived the orthotropic elastic constants: Young’s modulus (E), Poisson’s ratio (ν) and shear modulus (G) at different radial positions (outer, central and inner) through micro-tensile testing and the digital image correlation (DIC) technique. Our results revealed that the Young’s modulus of bamboo exhibited a characteristic orthotropic behavior irrespective of radial position. The ratio of E in the L, T and R directions (EL:ET:ER) was 6.05:1.08:1, 5.12:1.17:1 and 8.02:1.58:1, respectively at the outer, central and inner positions. With increasing fiber fraction, ν (except νRT) demonstrated an upward trend. Under main axis tension, fiber pull-out and brittle fracture were the main failure modes, whereas off-axis tension exposed the vulnerable interface between fibers and parenchyma cells. The enhancement effect of the gradient structure in the L and T directions was more prominent, resulting in a consistent deformation pattern from the inner to outer positions. However, strain localization was found when tensioning through the R direction. Leveraging the derived orthotropic elastic constants, we visualized the three-dimensional elastic behavior of bamboo by body deformation. Bamboo at the outer position exhibited quasi-isotropic behavior in the RT plane due to the high fiber fraction. This study provides critical experimental evidence for the orthotropic behavior of bamboo at different radial positions and valuable data for mechanical modeling and practical applications involving bamboo.

A micromechanical cyclic damage model for high cycle fatigue failure of short fiber reinforced composites

This paper presents a micromechanical high cycle fatigue damage model for short fiber reinforced composite materials. Because the damage processes within such materials are influenced strongly by their microstructure, we use a mean field homogenization framework to compute the macroscopic behavior of the composite as well as the microscopic stresses and strains in the constituent phases. This allows us to account for damage phenomena related to both the fiber phase as well as in the matrix material. Fiber and fiber-interface damage is modeled using a Tsai–Wu and Weibull-based approach and the progressive damage due to cyclic loading is described by a progressive matrix damage model. The latter includes a novel coupling term in which the matrix damage progression is linked to the damage state of the reinforcing fibers. A cycle-based numerical formulation is used to overcome the computational limits of such load cases in the time domain. While the approaches are in principle applicable to different types of fiber–matrix composite, a short glass fiber reinforced polyamide 6.6 is used as an example material, for which microstructural analyses as well as tensile and fatigue tests are reported. The model’s capabilities with regard to complex fiber orientations and different fiber fractions are studied using different grades of this material class. Furthermore, the model is analyzed via benchmarks of the numerical schemes and by parameter sensitivity studies. The results show that the approach is capable of modeling the complex and microstructure-dependent fatigue damage and fatigue limits for the different material grades with limitations only becoming visible at very high fiber fractions.

Highly effective fractionation chemistry to overcome the recalcitrance of softwood lignocellulose

The efficient fractionation and thus production of individual biomass components are pivotal processes in the biorefinery concept. However, the recalcitrant nature of lignocellulose biomass, especially in the case of softwood, is one of the main obstacles to the wider application of biomass-based chemicals and materials. In this study, the use of aqueous acidic systems in the presence of thiourea was studied for the fractionation of softwood in mild conditions. Despite relatively low temperature (100 °C) and treatment times (30–90 min), notable high lignin removal efficiency (approximately 90 %) was obtained. Chemical characterization and the isolation of minor fraction of cationic, water-soluble lignin indicated that the fractionation proceed via nucleophilic addition of thiourea to lignin, resulting in dissolution of lignin in acidic water in relatively mild conditions. Besides high fractionation efficiency, both fiber and lignin fractions were obtained with bright color, significantly elevating their usability in material applications.

Fatigue behavior of unidirectional fiber‐reinforced pultruded composites with high volume fiber fraction

AbstractPultrusion is a high‐volume manufacturing process for fiber‐reinforced polymer (FRP) composites ensuring high strength and quality products. However, research studies are very limited on the fatigue behavior of these products, especially with unidirectional fiber alignment. This study investigates the fatigue behavior of the unidirectional pultruded glass FRP (GFRP) composites with high fiber volume fraction ( ). Tension–tension fatigue loading was applied with different levels of applied stress, frequency, and gripping condition until failure. Results showed that the high composites have significantly low fatigue life cycle. Moreover, increasing the frequency showed better fatigue resistance, while the tabs geometry has insignificant effect on the fatigue behavior of the dog‐bone shaped specimens. Comparison with available literature showed that GFRP composites with high have lower fatigue performance than those with low . A fatigue capacity reduction factor is also proposed for unidirectional GFRP composites as a function of the .

Associating Compositional, Nutritional and Techno-Functional Characteristics of Faba Bean (Vicia faba L.) Protein Isolates and Their Production Side-Streams with Potential Food Applications.

Faba beans (Vicia faba L.) show exciting prospects as a sustainable source of protein and fibre, with the potential to transition to a more sustainable food production. This study reveals the compositional, nutritional and techno-functional characteristics of two protein isolates from faba beans (Vicia faba L.), a high-starch fraction and a high-fibre side-stream. During the analysis of those four ingredients, particular attention was paid to the isolates' protein profile and the side-streams' carbohydrate composition. The isoelectric precipitated protein isolate 1 showed a protein content of 72.64 ± 0.31% DM. It exhibited low solubility but superior digestibility and high foam stability. High foaming capacity and low protein digestibility were observed for protein isolate 2, with a protein content of 71.37 ± 0.93% DM. This fraction was highly soluble and consisted primarily of low molecular weight proteins. The high-starch fraction contained 83.87 ± 3.07% DM starch, of which about 66% was resistant starch. Over 65% of the high-fibre fraction was insoluble dietary fibre. The findings of this study provide a detailed understanding of different production fractions of faba beans, which is of great value for future product development.

High fiber fraction DDGS – A functional filler for manufacturing low-density particleboards

Increasing demand for wood in the particleboard industry, its associated cost, and the potential health issues with chemical resins have led to a search for using environment friendly renewable agricultural products to replace the wood particles. The objective of this study was to evaluate the properties of particleboards manufactured from renewable products such as wheat straw and the high fiber fraction of distillers dried grains with solubles (DDGS). The high fiber fraction of the DDGS was obtained by sieving and aspiration to get two fractions - one with high protein and another with high neutral detergent fiber (NDF) content compared with the original DDGS. The number 20 sieved and aspirated lighter fraction (SA#20-L) had the highest NDF content at 25.44% higher than the original DDGS. Therefore, this SA#20-L fraction was selected for particleboard manufacturing. Particle size distribution (PSD) was analyzed using ∑Volume machine vision approach to study the effect of particle morphology and size on properties of boards. Low-density particleboards were made from SA#20-L DDGS and wheat straw at three different loadings of DDGS (25%, 50%, and 75%) using 3% (dry basis) phenol formaldehyde (PF) resin. Particleboards with the same the DDGS loading and processing conditions were also manufactured from original DDGS to test the effectiveness of using the high fiber DDGS for manufacturing particleboards. The inclusion of DDGS (both SA#20-L and original) at 25% loading in the wheat straw boards had comparable mechanical properties to control wheat straw particleboards. With the inclusion of even higher DDGS loading (50% and 75%), physical properties were significantly improved as compared to control, but mechanical properties declined. Modulus of Elasticity (MOE) was superior for high fiber DDGS than particleboards made from the original DDGS. Other mechanical properties, however, were better for the original DDGS. At 25% DDGS loading, both SA#20-L and original DDGS met the ANSI 208.1 standard for MOE, modulus of rupture, and internal bond values for low-density particleboards.

Recycling of Waste MDF by Steam Refining: Evaluation of Fiber and Paper Strength Properties

Currently, most of the collected waste medium-density fiberboards (MDF) is incinerated or landfilled, as economically viable recycling methods are yet to be developed. By steam refining waste medium-density fiberboards (MDF), it is possible to hydrolyze the incorporated resins and isolate a high yield fiber fraction. Further refining of the steam treated fibers might enable the fibers to be utilized in applications such as paper packaging, facilitating a cascading use of the waste material stream. To this end, intimate knowledge of the material is needed. In this study, the steam refined fibers of two waste MDF samples containing differing amounts of softwood and hardwood underwent refining and beating. The resulting fibers were characterized regarding their morphology and paper test sheets were produced to evaluate their strength (compression-, tensile- and tear-strength). Distinct differences in response to refining between the MDF samples were apparent. For the sample with the higher hardwood share an increase in strength properties with increasing steam treatment severities could be observed and it was possible to produce test sheets with comparable compression strength to recycled pulp for industrial corrugated paperboard. For the sample with a higher share of softwood, the steam treatment severity did not show any influence on fiber morphology or paper properties, and the resulting paper strength was low in comparison to the other steam refined waste MDF sample.Graphic

Effect of fiber fraction on the physical and mechanical properties of short areca sheath fiber reinforced polymer composite

The fiber fraction in a composite will have a significant influence on its behavioural aspects and is reported in the current study. With different fiber fractions (0, 12, 24, 36 and 48 wt%) of the areca sheath fiber reinforcing agent, composite specimens were prepared and its physical and mechanical properties were examined. The measured density of the neat epoxy to the higher fiber fraction composite specimen (48 wt%) varies from 1.147 to 0.9524 g/cm 3 , from which it is evident that the density decreases with increase in the fiber concentration. On the other hand, void fraction for a neat epoxy is 0.26% which increases with the increase in the fiber concentration and is 6.14% for the 48 wt% fiber loaded specimen. An optimum values of investigated mechanical properties such as the hardness (72.56 HRB), Young’s modulus (1.98 GPa), and the Impact strength (4.724 J) have been observed with the increase in fibre fraction. The flexural strength for the neat epoxy is 46.28 MPa starts decreasing with the inclusion of fibers and reaches 12.05 MPa at a higher fraction of 48 wt%. The similar declining behaviour may be observed for the flexural modulus of 0.26 GPa and tensile strength of 14.02 MPa at high fiber fraction.

Effect of Varying Steel Fiber Content on Strength and Permeability Characteristics of High Strength Concrete with Micro Silica.

For the efficient and durable design of concrete, the role of fiber-reinforcements with mineral admixtures needs to be properly investigated considering various factors such as contents of fibers and potential supplementary cementitious material. Interactive effects of fibers and mineral admixtures are also needed to be appropriately studied. In this paper, properties of concrete were investigated with individual and combined incorporation of steel fiber (SF) and micro-silica (MS). SF was used at six different levels i.e., low fiber volume (0.05% and 0.1%), medium fiber volume (0.25% and 0.5%) and high fiber volume (1% and 2%). Each volume fraction of SF was investigated with 0%, 5% and 10% MS as by volume of binder. All concrete mixtures were assessed based on the results of important mechanical and permeability tests. The results revealed that varying fiber dosage showed mixed effects on the compressive (compressive strength and elastic modulus) and permeability (water absorption and chloride ion penetration) properties of concrete. Generally, low to medium volume fractions of fibers were useful in advancing the compressive strength and elastic modulus of concrete, whereas high fiber fractions showed detrimental effects on compressive strength and permeability resistance. The addition of MS with SF is not only beneficial to boost the strength properties, but it also improves the interaction between fibers and binder matrix. MS minimizes the negative effects of high fiber doses on the properties of concrete.

Anisotropic Dry Sliding Friction and Wear Properties of a Novel Stainless Steel/ZA8 Alloy Interpenetrating Phase Composite Produced by Squeeze Casting

Novel interpenetrating phase composites (IPCs) were produced by infiltrating ZA8 alloy into sintered 304 stainless steel fiber preforms through squeeze casting. Microstructural characteristics and dry sliding wear behavior of the IPCs at room and elevated temperatures under different applied loads were investigated. The results indicate that the microstructures and wear behavior of the IPCs exhibit anisotropy. The IPCs have better wear resistance properties and lower friction coefficients in the longitudinal direction compared to the radial direction. Compared with the unreinforced alloy, the composites exhibit lower friction coefficients at both room and elevated temperatures, and the wear rate of the IPC is higher at room temperature and significantly lower at 120 °C. The friction coefficients and wear rates of the IPCs first decrease and then increase with increasing fiber fraction. The IPC with 35.98 vol% has the best wear resistance. For the IPCs, a higher applied load leads to a higher friction coefficient and wear rate. The predominant wear mechanisms for the ZA8 alloy are delamination wear, which becomes more severe with increasing applied load at room temperature, and plastic deformation and adhesive wear at 120 °C, and the IPCs show predominant abrasive (ploughing) wear and slight delamination wear. Abrasive wear becomes more severe for a too high fiber fraction at both temperatures.

High-pressure interfacial impregnation by micro-screw in-situ extrusion for 3D printed continuous carbon fiber reinforced nylon composites

A micro-screw in-situ extrusion process was utilized to obtain high pressure for good impregnation and high fiber fraction of 3D printed continuous carbon fiber reinforced nylon (PA12) composites. Nylon pellets and different carbon fiber strand bundles (1 K and 3 K) were used as raw materials to print composites with different process parameters. Almost full impregnation for 1 K continuous carbon fiber (CCF) reinforced PA12 composites (1 K-CCF/PA12) with only 0.15% porosity and good impregnation for 3 K continuous carbon fiber reinforced PA12 composites (3 K-CCF/PA12) with 2.62% porosity achieved. Fiber volume fraction was dramatically improved from 31.9 vol% for 1 K-CCF/PA12 to 50.2 vol% for 3 K-CCF/PA12. Mechanical properties of different composites were measured systematically. Excellent longitudinal tensile strength and modulus of 735.7 MPa and 79.5 GPa, and simultaneously flexural strength and modulus of 772.6 MPa and 85.3 GPa for 3 K-CCF/PA12 were obtained. This novel 3D printing of continuous fiber reinforced composite process realized the integration of composites preparation and formation with enhanced impregnation, high fiber fraction and mechanical performance which could expand the applications of this technology to more and more industry fields.

An automatic methodology to CT-scans of 2D woven textile fabrics to structured finite element and voxel meshes

This paper presents a novel methodology to isolate the individual tow information contained within relatively low resolution µCT scans of real textile specimens. The proposed method can process high fibre fraction (Vf > 0.60) datasets in a fast and automated manner with minimal user interaction. The methodology has been validated qualitatively and quantitatively. The geometric description of the isolated tows can be used to create structured finite element meshes and voxel meshes, that contain the local tow information such as fibre volume fraction and fibre direction using an in-house meshing algorithm. The structured finite element meshes can be used as initial geometry for textile compaction simulations. The voxel meshes can be used directly for a flow simulation to predict the textile permeability. Finally, a methodology to observe the geometrical evolution of the same tows from different µCT datasets is also presented.

In-depth study of the changes in properties and molecular structure of cassava starch during resistant dextrin preparation

Physical, chemical and thermal properties, as well as molecular structure of cassava-based resistant dextrins prepared under different dextrinization conditions (0.04–0.10% HCl, 100–120 °C, 60–180 min) were determined. Increasing acid concentration, temperature and heating time resulted in the products with darker color, higher solubility, reducing sugar content, total dietary fiber and proportion of high molecular weight fiber fraction. An endothermic peak at 45–70 °C, having enthalpy of 1.66–2.14 J/g, was found from the samples processed under mild conditions (0.04–0.08% HCl, 100 °C, 60 min). However, harsher dextrinization conditions eliminated this endotherm. Dextrinization led to 1000-fold decrease in weight-average molecular weight (Mw) of the products, comparing to the native starch. Stronger processing conditions yielded the resistant dextrins with slightly higher Mw but composing of shorter branched chains. During dextrinization, hydrolysis was a predominant step, while transglucosidation and repolymerization played key roles in modifying molecular structure and properties, especially dietary fiber content, of resistant dextrins.

Cure kinetics and viscosity modeling for the optimization of cure cycles in a vacuum-bag-only prepreg process

This study focuses on the development of a process-based simulation model coupled with differential scanning calorimetry (DSC) and dynamic mechanical analyzer (DMA) experiments. The cure kinetics and rheology of an epoxy-amine resin were characterized in order to predict the degree of cure and viscosity behavior in an out-of-autoclave (OOA) process condition. Both phenomenological reactions and chemo-rheological models were applied to effectively predict the degree of cure and resin viscosity. Using these results, it is possible to predict the minimum viscosity, gelation, and vitrification, which are the main process factors of the multi-stepped cure cycles, and reduce the number of process trials. It was found that there was a good correlation between the experimental results and model predictions under isothermal and non-isothermal temperature profiles. Furthermore, this study demonstrates that there is an additional scope for optimization in the conventional cure cycles recommended by prepreg manufacturers, especially when a low viscous state is required. The optimized cure cycle led to a substantially high fiber fraction (58.96 vol%) and a low void content (0.15 vol%), as compared to the conventional cure cycles.

A Comparison of the Properties of Carbon Fiber Epoxy Composites Produced by Non-autoclave with Vacuum Bag Only Prepreg and Autoclave Process

The non-autoclave curing technique with vacuum bag only (VBO) prepreg has been conceived as a cost-effective manufacturing method for producing high-quality composite part. This study demonstrated the feasibility of improving composite part’s performances and established the effective mitigation strategies for manufacturing induced defects, such as internal voids and surface porosity. The experimental results highlighted the fact that voids and surface porosity were clearly dependent on the resin viscosity state at an intermediate dwell stage of the curing process. Thereafter, the enhancement of resin flow could lead to achieving high quality parts with minimal void content (1.3%) and high fiber fraction (53 vol.%). The mechanical testing showed comparable in-plane shear and compressive strength to conventional autoclave. The microscopic observations also supported the evidence of improved interfacial bonding in terms of excellent fiber wet-out and minimal void content for the optimized cure cycle condition.

Mechanical Properties of GF/pCBT Composites and Their Fusion-Bonded Joints: Influence of Process Parameters

High melting viscosity of thermoplastic composites gives no way of using substantial volume fractions of reinforcing agents. This problem can be solved by in-situ polymerization of an extremely low-viscosity cyclic butylene terephthalate (CBT) resin. Continuous glass fiber-reinforced poly(cyclic butylene terephthalate) (GF/pCBT) composites with high fiber fractions were manufactured, and the mechanical properties as a function of the catalyst mass fraction and fiber filling ratio were studied. The longitudinal tensile strength of the composites was enhanced by increasing the fiber volume fraction, and the influence of the fiber fraction on the bending strength of high fiber filling-ratio composites was evaluated. Furthermore, the mechanical properties and failure modes of GF/pCBT fusion-bonded joints with different number of bonding areas of different lengths were investigated. It was found that high-strength composite materials can be obtained, which are applicable for fusion-bonded structures.

Composição nutricional e digestibilidade “in vitro” de genótipos de milho produzidos em dois anos agrícolas

The objective of this study was to evaluate the chemical composition, quantitatively characterize, in a comparative way, the carbohydrate fractions of commercial corn hybrids and of materials from crossing between hybrids for silage production. Therefore, 14 multiple hybrids, 7 commercial hybrids, 7 selffertilized from commercial hybrids progenies and 2 controls were evaluated in two agricultural years. The 2B710 hybrid showed high dry matter in vitro digestibility in the first year and fiber fraction in the two years of evaluation. The progeny P30P34 x P30P34 showed high dry matter digestibility and fiber fraction in two years. The highest fraction of non-fibrous carbohydrates (A+B1) was found for the crosses IMPACTO x CD308 and P30R50 x CD308 for the first and second year respectively, indicating a greater efficiency in providing readily available energy in the rumen. The significant interactions between corn hybrids and agricultural years for chemical composition showed that the growing environment has great influence on the nutritional composition, leading to the necessity of evaluating multiple environments in order to select corn for silage production.

Effect of mixing conditions on the morphology and performance of fiber-reinforced polyurethane foam

Polyol derived from soybean oil was used as a natural source preparation to create an environmentally friendly polyurethane foam. In order to stiffen these foams, wood fibers were added to provide reinforcement at low cost, while preserving the environmental friendly nature of the material. Mixing is a crucial step in the manufacture of reinforced foams and determines the fiber distribution and cell structure and hence the performance of the material. In this study, the effect of stirring variables on the mechanical properties of polyurethane foams was investigated and foams made using hand mixing were compared to foams made with a mechanical stirrer. Cell morphologies of the reinforced foams were characterized using scanning electron microscopy, X-ray computed tomography, and 3D stereo microscopy. The mechanical performance of the reinforced foam was essentially independent of stirring time and mainly depended on the variation in stirring rate. For foams made with high fiber fractions using a mechanical stirrer, the fibers were not as effective in increasing the compressive strength and modulus as they were in foams prepared by hand stirring. This suggests that mechanical stirring causes damage to the fibers, particularly at high fiber content.

Development and Shelf Stability of Natural Fibre Rich Retort Pouch Ready to Eat Products

The new frontier in the food research is the role of non nutritive components in human health. In the recent past, the importance of dietary fibre in the diet has been increased as a functional ingredient which has opened up a potential market for fibre rich products. The by products available during processing of plant foods are considered as promising source of functional fibres. The aim of the present study was to develop fibre rich products using the natural fibre such as ashgourd (Benincasa hispida) fibre, with high soluble fibre fraction. Ready-to-eat fibre rich Bisi bele bath and vegetable pulav were developed with the optimization of fibre using statistical design software. Fibre, fat and spice mixtures were independent variables with the other components as fixed factors. Since the product acceptance is more dependent on volatile compound form intern the flavour, as well as depends on the test, appearance, colour, texture which are the sensory attributes, total volatiles and sensory attributes were selected as responses. While in the fibre rich vegetable pulav water, fibre and spice mixtures were the independent variables. Both the products were showing good acceptability i.e. in the case of bisi bele bhath 7.1 and in the case of vegetable pulav 6.5 on a 9 point hedonic scale after 6 months of storage at room temperature. The dietary fibre profile of bisi bele bhath was 1.1% soluble fibre and 4.4% insoluble fibre while vegetable pulav had 6.2% insoluble and 1.54% soluble fibre fraction. The products were safe and had an established shelf life of 6 months.

Hemp yarn reinforced composites – III. Moisture content and dimensional changes

Based on a comprehensive set of experimental data it is demonstrated that the moisture properties of aligned hemp fibre yarn/thermoplastic matrix composites are showing low moisture sorption capacity and low dimensional changes. Using a reference humidity of 65% RH, and a common span of ambient humidity levels of 33% and 85% RH, the relative moisture content of composites with a high fibre fraction is ranging from −0.009 at 33% RH and+0.016 at 85% RH, and this lead to relative transverse hygral strains in the range of only −0.007 to+0.011. The axial hygral strain is practically zero. The moisture content of the composites is shown to be well predicted by a mixtures relationship using the measured moisture contents of the constituents. The dimensional changes of the composites are well predicted by micromechanical models of the transverse and axial hygral strains.