Increasing Fiber Content Research Articles

Effect of Fiber Type and Content on Surface Quality and Removal Mechanism of Fiber-Reinforced Polyetheretherketone in Ultra-Precision Grinding.

Polyetheretherketone (PEEK) is a promising thermo-plastic polymer material due to its excellent mechanical properties. To further improve the mechanical properties of PEEK, different kinds of short fibers are added into the PEEK matrix. The grinding machinability of short-fiber-reinforced PEEK varies with the effect of fiber type and content. Therefore, it is crucial to investigate the surface quality and removal mechanism of fiber-reinforced PEEK in ultra-precision grinding. In this paper, different fiber types and mass fractions of short-fiber-reinforced PEEK, including carbon-fiber-reinforced PEEK (CF/PEEK) and glass-fiber-reinforced PEEK (GF/PEEK), are employed. The grinding machinability of short-fiber-reinforced PEEK was investigated using grinding experiments with grinding wheels of different grit sizes. The effects of the fiber type and mass fraction on the surface quality and removal mechanism during grinding were discussed. The results showed that the brittle–ductile transition depth of carbon fiber was much larger than that of glass fiber, so it was easier to achieve ductile removal in grinding with the carbon fiber. Therefore, the ground surface roughness of CF/PEEK was smaller than that of GF/PEEK under the same grinding conditions. With the increase in carbon fiber mass fraction, the ground surface roughness of CF/PEEK decreased due to the higher hardness. The brittle–ductile transition depth of glass fiber was small, and it was easy to achieve brittle removal when grinding. When the glass fiber removal mode was brittle removal, the GF/PEEK surface roughness increased with the increase in glass fiber content.

Addition of Soluble Fiber in Low-Fat Purified Diets Maintains Cecal and Colonic Morphology, Modulates Bacterial Populations and Predicted Functions, and Improves Glucose Tolerance Compared with Traditional AIN Diets in Male Mice

ABSTRACTBackgroundPurified diets (PDs) contain refined ingredients with one main nutrient, allowing for greater control relative to grain-based diets (GBDs), which contain unrefined grains and animal byproducts. Traditional PDs like the American Institute of Nutrition (AIN)-76A (76A) and AIN-93G (93G) can negatively impact metabolic and gut health when fed long term, in part due to lower total fiber, no soluble fiber, and higher sucrose content.ObjectiveTwo studies were conducted to determine how PDs with reduced sucrose and increased fiber (soluble and insoluble) influence metabolic and gut health in mice compared with traditional AIN PDs or GBDs.MethodsIn study 1, C57Bl/6N mice (n = 75) consumed a GBD [LabDiet 5002 (5002)], 76A, 93G, or 2 PDs with reduced sucrose and higher fiber for 88 d. Body composition and metabolic parameters were assessed. In study 2, C57Bl/6N mice (n = 54) consumed either 2 GBDs (LabDiet 5001 or 5002) or PDs with different types/levels of fiber for 14 d. Microbiome alterations and predicted functional metagenomic changes were measured.ResultsThe PD with 75 g cellulose and 25 g inulin per 4084 kcals marginally influenced body weight and adiposity, but improved glucose tolerance relative to 93G (P = 0.0131) and 76A (P = 0.0014). Cecal and colonic weights were lower in mice fed cellulose-based PDs compared with those fed GBDs and soluble-fiber PDs. Soluble-fiber PDs reduced alpha diversity and showed similar beta diversity, which differed from cellulose-based PDs and GBDs. Certain genera associated with improved gut health such as Bifidobacteria and Akkermansia were significantly elevated by soluble-fiber PDs (P ≤ 0.01). Metabolic pathways related to carbohydrate and fatty acid metabolism were affected by PDs.ConclusionsPDs formulated with lower sucrose and increased fiber content, particularly soluble fiber, blunted elevations in metabolic parameters and favorably impacted the microbiota and metagenome in C57BL/6N mice.

Impact of germination on the proximate composition, functional properties, and structural characteristics of black soybean ( Glycine max L. Merr)

This study aimed to investigate the impact of germination on the quality of black soybean flour (BSF). The black soybeans were germinated for different time period (24, 48, and 72 h), and the impact on proximate composition, functional, structural, and antioxidant properties of the obtained flour was evaluated. Germination process resulted in significant (p ≤ 0.05) increase in protein (39.46 ± 0.08–43.30 ± 0.05 g/100 g), crude fiber (7.55 ± 0.15–10.31 ± 0.16 g/100 g), and ash (5.95 ± 0.04–6.28 ± 0.01 g/100 g) content as compared with raw black soybean flour (RBSF). Further, significant variation in color attributes, functional properties, and pasting characteristics of raw and germinated black soybean flour (GBSF) was observed. Significant increase in total phenolic content (6.76 ± 0.05 to 9.30 ± 0.04 mg GAE/g), total flavonoid content (2.45 ± 0.04 to 4.32 ± 0.02 mg QE/g), and DPPH radical scavenging activity (41.31%–60.20%) was observed post germination (24–72 h). Scanning electron micrographs (SEMs) showed that germination resulted in microstructural changes in starch and protein matrix owing to activation of hydrolytic enzymes. Further, X-ray diffraction patterns elucidate significant reduction in crystallinity of GBSF (42.54%–44.48% for 24–72 h) in comparison to RBSF (45.75%).

Study on Evolution Law of Pore Structure and Frost Resistance of High-Performance Activated Cement-Based Composites in Severe Cold Area

In order to explore the frost resistance of high-performance activated cement-based composites(HACC), The freeze-thaw cycle test of HACC with different water-binder ratio and basalt fiber content was carried out, the mass loss rate, relative dynamic elastic modulus and related pore structure parameters of different freeze-thaw cycles were measured, and the influence of different factors on the frost resistance of HACC was studied, and the variation law of pore structure parameters with freeze-thaw cycles was explored. The results show that the mass loss rate of high performance cement-based composites has a small range, the maximum is less than 1% during failure, and the relative dynamic modulus changes significantly, which is the main indicator to evaluate the freeze-thaw failure of HACC; The frost resistance of HACC decreased gradually with the increase of the water-binder ratio, and showed a change rule of first increasing and then decreasing with the increase of basalt fiber content; HACC have good frost resistance when the air content is 3% ~ 4%. The bubble chord length is directly related to the freeze-thaw deterioration characteristics of HACC, and the bubble chord length reflects the frost resistance of HACC to some extent.

Study on the thermal and mechanical properties of steel fibre reinforced PCM-HSB concrete for high performance in energy piles

In this study, a hollow steel ball (HSB) is used to macro-encapsulate the phase change materials (PCM) to obtain PCM-HSB aggregates. Furthermore, the PCM-HSBs were incorporated with steel fibres to improve the thermal and mechanical properties of concrete. The effect of the volume content (0.35, 0.7, and 1.05 vol%) of the steel fibre and the thickness of HSB (0.3 and 1 mm) on the thermal and mechanical properties of the steel fibre reinforced PCM-HSB concrete was evaluated. The test results demonstrated that the thermal conductivity and compressive strength of the PCM-HSB concrete significantly increased with an increase in the steel fibre content and HSB thickness. The addition of 0.35% steel fibre improved the thermal conductivity of the PCM-HSB concrete by 71% due to the bridge function of the scattered steel fibres in the concrete matrix. However, the thermal conductivity decreased when the high steel fibre content was increased to1.05 vol% due to fibre agglomeration. Moreover, compared with that of the plain PCM-HSB concrete, PCM-HSB concrete with 0.7 vol% steel fibre increased the compressive strength of the concrete by 63%. The proposed fibre reinforced PCM-HSB can significantly improve the heat capacity and bearing capacity of concrete, which can ensure potential applications of energy piles.

Influence of Marble Powder and Polypropylene Fibers on the Strength and Durability Properties of Self-Compacting Concrete (SCC)

The purpose of this study was to investigate the effect of polypropylene fiber reinforced self-compacting concrete (SCC) at both the fresh and hardened stages, as well as their durability behavior. Properties of marble powder-based fiber reinforced SCC at fresh state were studied by means of slump flow diameter and flow time, V-funnel, and L-box test. The concrete properties at the hardened state were examined regarding compressive strength, split tensile strength, and flexural strength. Cement was replaced with marble powder with a substituting ratio of 4%, 8%, 12%, and 16% while polypropylene fibers were added as 0.1%, 0.2%, 0.3%, and 0.4%. The durability properties were analysed in the form of water permeability and chloride migration. In accordance with the outcomes of the tests, the workability of SCC deteriorated with an increase in fiber content, although it performed effectively at higher marble dosages. There was little impact of fibers on compressive strength and water permeability property of SCC. However, by adding the fibers in SCC improved both the split tensile strength and flexural strength by 16.92% and 11.36%, respectively. The addition of marble powder showed a synergetic effect with polypropylene fibers, which showed its applicability in SCC. The chloride resistance was improved at lower content of polypropylene fiber addition. For optimizing polypropylene fibers (pp) and marble powder substitution, the polynomial work expectation justifies the response surface technique (RSM). When a p value of 0.05 is used to analyse the variation in the (Linear-ANOVA), the model is considered statistically significant. Performance of concrete was greatly enhanced by substituting 12% marble powder with cement and adding 3% polypropylene fiber.

Inulin from Globe Artichoke Roots: A Promising Ingredient for the Production of Functional Fresh Pasta.

Globe artichoke roots represent an alternative and sustainable source for inulin extraction and are well-noted for their technological and functional properties. Therefore, the aim of our study was to exploit inulin with high degree of polymerization as a replacement of durum wheat semolina for the production of functional fresh pasta. The effect of increased level of substitution (5, 10, 15%) on cooking, structural, sensory, and nutritional properties were evaluated and compared with a control sample consisting exclusively of durum wheat semolina. Inulin addition caused changes to internal structure as evaluated by scanning electron microscopy. The enriched samples showed a lower swelling index, an increasing cooking time, and values of cooking loss (2.37–3.62%), mainly due to the leaching of inulin into the cooking water. Cooked and raw enriched pasta was significantly darker and firmer than the control, but the sensory attributes were not negatively affected, especially at 5 and 10% of substitution levels. The increase of dietary fiber content in enriched pasta (3.44–12.41 g/100 g) resulted in a significant reduction of glycaemic index (pGI) and starch hydrolysis (HI). After gastrointestinal digestion, inulin-enriched pasta increased prebiotic growth able to significantly reduce E. coli cell density.

Suffusion restraint in gap-graded soil reinforced with fibers

To study how gap-graded soil reinforced with fibers of different types restrains suffusion in embankment dams, the hydraulic response of fiber-reinforced soil (FRS) containing polypropylene fibers (PPF), coir fibers (CF) or basalt-tape fibers (BTF) was investigated in one-dimensional seepage tests. The critical hydraulic gradient and fine-particle loss of the FRS were analysed quantitatively by changing the fiber type, fiber content, and reinforcement-layer thickness. The test results show that the three types of FRS all had restraining effect on the development of suffusion. The netting reinforcement effect of PPF was the best, followed by the water absorption and expansion of CF to reduce pore volume, and finally the effect of BTF was to block migration channels under the same reinforcement conditions. With increasing fiber content and the reinforcement-layer thickness, the critical onset hydraulic gradient (icr,onset), and critical failure hydraulic gradient (icr,failure) increased, improving the internal erosion resistance of gap-graded soils against suffusion. The fine-particles loss decreased and the restraint rate of fine-particle loss (RF) increased meant that the permeability stability of soil was enhanced. Linear regression analysis showed that the reinforcement-layer thickness has greater influence on restraining effect parameters than fiber content.

PHYSICOCHEMICAL, MICROSTRUCTURE AND SENSORY PROPERTIES OF NOODLE ENRICHED WITH PUMPKIN (CUCURBITA MOSCHATA) POWDER

Pumpkin (Cucurbita moschata) is a fruit that contains large amount of dietary fiber. In this study, noodles were produced by substituting wheat flour with pumpkin powder at two concentrations (5% and 10%). The resulting noodles were then evaluated in terms of sensory, physicochemical, microstructure, and cooking properties. The addition of pumpkin powder caused a significant increase in ash, dietary fiber, Mg, K and Zn content, cooking loss, water absorption capacity and adhesiveness value, and a significant decrease in protein, fat and carbohydrate content, energy value, cohesiveness, resilience, gumminess, springiness and chewiness values. It was determined from microstructure images that pumpkin powder addition in the noodle formulation caused an interruption in the gluten-starch matrix. Control sample had significantly lower a* and b* values and higher L* values than the enriched samples. The noodles made with pumpkin powder received significantly higher sensory scores with regard to overall acceptability, flavor and color.

Experimental Study on Frost Heave Behavior of Steel Fiber Improved Soil

The incorporation of steel fibers into the natural soil is generally considered to be a novel and effective way to reduce the amount of frost heave induced by an artificial freezing process in underground engineering. In order to analyze the frost heave behavior of the steel fiber improved soil, a one-dimensional frost heave test under the open recharge system was conducted in this paper, focusing on the influence of steel fiber content, size, and soil properties. The results show that small amounts of steel fibers in the soil will not significantly affect the freezing process and temperature distribution, while the water-conducting properties of the steel fibers and the effect of limiting the ice lens growth can reduce the frost heave rate of the samples incorporated with 0.5% steel fibers by 26.93%. At the same time, the reduction effect of the frost heave rate increases linearly with the increase of steel fiber content and length but weakens with the increase of steel fiber diameter. In terms of soil property influence, the frost heave rate of the clay samples was reduced by 14.31% compared to the silt samples, while the water migration was reduced by 11.99%. In addition, the cementation of the steel fibers with the soil will also inhibit the growth of the ice lens and reduce the external water migration, thus significantly lowering the frost heave rate. The results can provide a reference for the research of the frost deformation of similar modified soils.

Experimental Study on Compressive and Flexural Performances of Polypropylene Fiber-Reinforced Concrete

Plain concrete (PC) has the disadvantages of easy cracking and low resistance to deformation. In practical engineering, steel fiber or polymer fiber is usually selected to improve the tensile and crack resistance of concrete. In this study, the polypropylene fiber (PPF) was added to the concrete with the content of 0, 0.6, 0.9, and 1.5 kg/m3. The compressive and flexural tests of PC and PPF-reinforced concrete (PPFRC) at 14, 28, and 60 days of curing were conducted. As the result, when the content of PPF exceeds to 1.2 kg/m3, the workability became worse. The compressive and flexural strength of PPFRC increased compared with PC. However, the increase of strength does not always increase with the increase of fiber content. The uniaxial compressive strength of the PPFRC with the PPF of 1.2 kg/m3 is the optimal at 14- and 28-day ages, which is 20.56% and 11.24% higher than PC, respectively. PPFRC with the PPF of 0.9 kg/m3 is best of all at 60 days, which is 19.68% higher than PC. The flexural strength of the PPFRC-0.9 is the highest. Furthermore, the CFEC and CTI of PPFRC are both higher than those of PC, indicating that it has significant crack resistance and toughness.

Fracture behavior of multi-scale nano-SiO2 and polyvinyl alcohol fiber reinforced cementitious composites under the complex environments

This paper aims to investigate the fracture properties and microscopic mechanisms of multi-scale nano-SiO2 (NS) and polyvinyl alcohol (PVA) fiber-reinforced cementitious composites (MNFRCC) in complex environments. The complex environment was the coupling effect of wet-thermal and chloride salt environments (CEWTSE) simulated by an environmental simulation test chamber. And the parameters of temperature, relative humidity (RH), mass fraction of NaCl solution, and action time were determined as 50 °C, 100 %, 5 %, and 30 d, respectively. The Double-K Fracture model (DKFM), boundary effect fracture model (BEM), and work fracture method (WFM) were used to reveal that PVA fiber and NS improved the fracture properties of MNFRCC under the CEWTSE. And when the contents of PVA fiber and NS were 1.2 % and 0.5 %, respectively, the fracture parameters were significantly improved. Based on the comparative analysis of DKFM and BEM, the reasonable fracture parameters could be obtained by linking them through the crack propagation length. Moreover, the fictitious crack growth lengths and characteristic cracks increased with the increase of PVA fiber contents. On the microscopic level, PVA fiber and NS improved pores, microcracks and interfacial transition zone in the MNFRCC.

Compressive Toughness Loss Rate and Softening Characteristic Analysis of Pasture Fiber-Rubber Powder Concrete

To develop the utilization of pasture fibers and waste tire rubber powder, the effect of different blending levels of modified pasture fibers (2 kg/m3, 3 kg/m3, and 4 kg/m3) on the loss rate of compressive toughness and softening characteristics of rubber powder concrete was studied. In addition, RapidAir457 system imaging analysis and microscopic electron microscope photo analysis were carried out to analyze the distribution pattern of modified pasture fibers and rubber powder in concrete. The results show that the peak load of concrete is higher than other pasture fiber dosing test groups when 3 kg/m3 is incorporated in 20 mesh and 60 mesh rubber powder. With the increase of pasture fiber content, the compressive toughness loss of MC60 group and MC80 group increased first and then decreased. The softening curve analysis showed that MC-3 was more capable of absorbing damage energy in the strain range of 0.0005–0.0009 than the MC-2 group. According to the RapidAir457 system imaging analysis, the pasture fibers form a web-like organization inside the concrete when the pasture fiber is mixed at 3 kg/m3.

Effect of carbon fiber on the properties of polymer cement based building sealant

AbstractThe working property, bond property, and mechanical property of five kinds of polymer cement based building sealant (PCBS) with different carbon fiber content were tested. The effect of carbon fiber on the properties of PCBS was discussed by analyzing the variation of the leveling performance, consistency, low temperature flexibility, surface dry time, elastic recovery rate, tensile mechanical property, and shear mechanical property of PCBS with carbon fiber content. And the modification mechanism of carbon fiber on PCBS was interpreted using scanning electron microscopy and mercury intrusion porosimetry techniques. The results shows that PCBS still has good working property and bonding property with carbon fiber addition. As the carbon fiber content increases, the leveling performance and low temperature flexibility of PCBS are unaltered., the consistency increases, while the surface drying time and elastic recovery rate decrease. The tensile and shear mechanical properties of PCBS can be improved by adding carbon fiber. With the increase of carbon fiber content, the strength performance indexes of PCBS increase, while the energy consumption performance indexes first increased followed by a decrease. When the carbon fiber content is 0.1%, the properties of PCBS is the best. The pore structure of PCBS gradually deteriorates, and the total porosity and the percentage of macropores increase with carbon fiber addition. Carbon fiber primarily exerts cracking resistance and internal deterioration effects in PCBS.

Research on the Mechanical and Physical Properties of Basalt Fiber-Reinforced Pervious Concrete.

The aim of this study was to investigate the properties of fiber-reinforced pervious concrete. Ordinary cement, silica fume, coarse aggregate, and basalt fibers were used to produce the concrete mix. The fibers were mixed with pervious concrete at the levels of 0 kg/m3, 2 kg/m3, 4 kg/m3, 6 kg/m3, and 8 kg/m3 to the investigate their influence on the mechanical and physical properties of pervious concrete. It could be observed that the cubic compressive strength, axial compressive strength, and flexural strength increased and then decreased as the content of basalt fiber increased, while the permeability and porosity of the pervious concrete decreased with the increase in the basalt fiber content. The mesostructure of pervious concrete was also studied through industrial computed tomography (ICT); the testing phenomenon showed that the fibers had a significant influence on the arrangement of the aggregate, cement paste, and the interfacial transition zone, and excessive basalt fiber resulted in poor characteristics of the interfacial transition zone (ITZ) and inferior strength properties. It was found that incorporating a basalt fiber content of 4 kg/m3 could achieve a balance between the mechanical and physical properties of pervious concrete, which was suitable for structural applications.

Cooking Quality and Chemical and Technological Characteristics of Wholegrain Einkorn Pasta Obtained from Micronized Flour.

The increased demand for healthier foods, the recognition of dry pasta as an ideal carrier of functional ingredients, and the current interest for ancient wheats such as einkorn motivated the present research. Two varieties of Triticum monococcum, namely cv Norberto and the free-threshing cv Hammurabi, were milled by ultra-fine milling process (micronization) to produce wholegrain spaghetti. Einkorn pasta was assessed in terms of technological and biochemical properties and cooking and sensorial quality and compared to durum wheat semolina pasta. Wholewheat einkorn pasta showed a threefold increase in total dietary fibre content as well as in total antioxidant capacity in comparison to the control. The level of resistant starch in cv Norberto resulted significantly higher respect to semolina and einkorn cv Hammurabi pasta. Despite the very weak einkorn gluten network, the sensory and instrumental assessment of pasta quality highlighted that einkorn spaghetti presented good sensorial properties related to their technological quality, in particular, for the overall judgment and firmness. Cultivar Hammurabi emerged as the preeminent compromise on the basis of technological performances together with chemical and sensorial aspects.

Development of a new magnesium oxychloride cement board by recycling of waste wood, rice husk ash and flue gas desulfurization gypsum

Recycling construction waste wood to produce magnesium oxychloride cement board (MOCB) is an eco-friendly and high-value strategy. The effects of extrusion force, admixtures, wood fiber content and size on the physical and mechanical properties of MOCB were systematically investigated in this study. The results show that an appropriate increase in the wood fiber content in MOCB can not only reduce the density but also increase its flexural strength, but the pulling force decreases due to the reduction of compactness. Meanwhile, the small-sized wood fiber is beneficial to the increase of density and pulling force of MOCB, and the appropriate increase of wood fiber size can improve its flexural strength and water resistance. Increasing the extrusion force can also enhance the flexural strength and pulling force by increasing the compactness of the sample, but it is detrimental to the development of water resistance. Appropriate amount of rice husk ash (RHA) can improve the mechanical properties and water resistance of MOCB. The incorporation of flue gas desulfurization gypsum (FG) reduces the strength of MOCB, but its water resistance is improved. In addition, RHA and FG-modified MOCBs indicate better environmental benefits and performance indicators (Thickness swelling and water absorption) compared to conventional resin-based particleboard and Portland cement-based particleboard. This study provides not only strategies for recycling waste wood, but also technical parameters for producing eco-friendly cement composite boards.

Effect of Single and Synergistic Reinforcement of PVA Fiber and Nano-SiO2 on Workability and Compressive Strength of Geopolymer Composites.

Geopolymer composites can be used as a proper substitute for ordinary Portland cement, which can reduce carbon dioxide (CO2) emissions and make rational use of industrial waste. In this study, an investigation of the workability and compressive strength of geopolymer composites was carried out through a series of experiments, such as slump flow test, consistency meter test and compressive strength test, to clarify the interaction mechanism among superplasticizer (SP), polyvinyl alcohol (PVA) fiber, Nano-SiO2 (NS) and geopolymer composites, thereby improving the properties of engineered composites. The results showed that with the increase in PVA fiber content, the flowability of geopolymer composites decreased, while the thixotropy increased. With the increase in the NS content, the flowability of geopolymer composites first increased and then decreased, reaching its best at 1.0%, while the thixotropy was the opposite. With the increase in the SP content, the flowability of geopolymer composites increased, while the thixotropy decreased. A significant correlation between thixotropy and flowability of geopolymer composites was found (R2 > 0.85). In addition, the incorporation of single PVA fiber or NS significantly improved the compressive strength of geopolymer composites. Specifically, the compressive strength of geopolymer composites with 0.8% content PVA fiber (60.3 MPa) was 33.4% higher than that without PVA fiber (45.2 MPa), and the compressive strength of geopolymer composites with 1.5% content NS (52.6 MPa) was 16.4% higher than that without NS (45.2 MPa). Considering the synergistic effect, it is found that the compressive strength of geopolymer composites (58.5–63.3 MPa) was significantly higher than that without PVA fiber (45.2–52.6 MPa). However, the flowability and compressive strength of geopolymer composites were only slightly improved compared to that without NS. With the increase in the SP content, the compressive strength of geopolymer composites showed a trend of a slight decrease on the whole. Consequently, the results of this study may be useful for further research in the field of repair and prevention of the delamination of composite structures.

Dynamic Mechanical Analysis and Ballistic Performance of Kenaf Fiber-Reinforced Epoxy Composites.

Several industry sectors have sought to develop materials that combine lightness, strength and cost-effectiveness. Natural lignocellulosic natural fibers have demonstrated to be efficient in replacing synthetic fibers, owing to several advantages such as costs 50% lower than that of synthetic fibers and promising mechanical specific properties. Polymeric matrix composites that use kenaf fibers as reinforcement have shown strength increases of over 600%. This work aims to evaluate the performance of epoxy matrix composites reinforced with kenaf fibers, by means of dynamic-mechanical analysis (DMA) and ballistic test. Through DMA, it was possible to obtain the curves of storage modulus (E′), loss modulus (E″) and damping factor, Tan , of the composites. The variation of E′ displayed an increase from 1540 MPa for the plain epoxy to 6550 MPa for the 30 vol.% kenaf fiber composites, which evidences the increase in viscoelastic stiffness of the composite. The increase in kenaf fiber content induced greater internal friction, resulting in superior E″. The Tan was considerably reduced with increasing reinforcement fraction, indicating better interfacial adhesion between the fiber and the matrix. Ballistic tests against 0.22 caliber ammunition revealed similar performance in terms of both residual and limit velocities for plain epoxy and 30 vol.% kenaf fiber composites. These results confirm the use of kenaf fiber as a promising reinforcement of polymer composites for automotive parts and encourage its possible application as a ballistic armor component.

Shear Strength Behavior of Fiber-Reinforced Soil: Experimental Investigation and Prediction Model

This paper presents a prediction model for the shear strength of fiber-reinforced soil. A series of triaxial compression tests were first conducted to investigate the influences of fiber content and fiber length on the shear strength behavior of fiber-reinforced soil under different confining pressures. Experimental results on the stress–strain relationship, shear strength improvement ratio, shear strength parameters, and reinforcement mechanism are presented and discussed. Results indicate that the shear strength of fiber-reinforced soil increases significantly with increasing fiber content, but there exists an optimal value for strength improvement. The fiber content and fiber length have little influence on the friction angle of fiber-reinforced soil, while the apparent cohesion increases significantly with increasing fiber content and fiber length. Based on the experimental data, a prediction model was proposed for the shear strength of fiber-reinforced soil using the concepts of equivalent apparent cohesion and equivalent normal stress. The model can capture the decrease in shear strength improvement effect due to excessive fibers and can predict the shear strength of fiber-reinforced soil with good accuracy using fiber parameters and shear strength parameters of unreinforced soil.