High-strength Composites Research Articles

Secondary Processing of Aramid with AWJ and Optimization with NSGA-III

The secondary operations of composite parts are performed following thermal cure processes, which generate the final dimensions with desired tolerance and quality specifications. High-strength composites, on the other hand, especially aramid fiber-reinforced polymers (AFRP), are not suitable for conventional machining operations due in part to high operational costs and limited surface quality characterized by fuzziness and delamination. Abrasive Water Jet (AWJ) has been recently shown promising results in obtaining improved surface quality while ensuring significant cost advantages. This study investigates the AWJ processing of AFRP by implementing the analysis of variance and response surface methods. The effects of the control parameters (sand ratio, pressure, stand-off-distance, and feed rate) on the surface quality metrics (surface roughness, kerf angle, and dimensional error) are identified and comparatively evaluated. The surface quality of the AWJ processed AFRP specimens are investigated using Scanning Electron Microscopy (SEM). The trade-offs between the measured tolerances and surface roughness values are identified via a new genetic algorithm approach: Non-dominated Sorting Genetic Algorithm (NSGA-III). Also, operation regions are determined using the generated Pareto curves while improving the quality of various features of an AFRP component, critical to its functional performance during extended service life. As a result, the lowest Ra values obtained were 4.135 µm for trimming, 5.962 µm for pocketing, and 4.696 µm for the hole-making operation. The maximum error in the accuracy of operating regions yields to 7% with independent measurements for validation.

PREPARATION OF CONCRETE BASED ON GLASS WASTE

PREPARATION OF CONCRETE BASED ON GLASS WASTE

A lightweight and high-strength epoxy composites based on graphene oxide modified kapok fibers

Lightweight and high-strength (LWHS) composites are widely used in aerospace, automotive and marine fields. However, it is difficult to maintain the strength of the material while decreasing its density, let alone increasing. In this work, inspired by the mechanism of fiber-reinforced polymers, a LWHS epoxy composite was constructed through hollow kapok fibers. Computational fluid dynamics simulations show that the hollow structure of kapok fiber can be effectively retained. The results show that the graphene oxide effectively improves the interfacial adhesion between kapok fiber and epoxy matrix. Decrease in specific gravity and the enhancement of mechanical properties can simultaneously realize in the LWHS composites via the interweaving of kapok fibers. At an optimal 1.5 wt% fiber content, the specific gravity of LWHS composites decreased by 20.3% while tensile strength, bending strength and compressive strength increased by 21.5%, 9.56% and 51.92%, respectively. Tensile modulus, bending modulus and compression modulus increased by 48.35%, 92.18% and 49.84%, respectively.

High-Strength Cement Composites Modified with a Complex Additive Hyper Plasticizer - Bentonite

The paper presents the results of research on creating a high-strength cement composite using a complex additive. The optimal concentrations of additives of the Odolit-K hyper plasticizer in combination with bentonite have been determined. A significant decrease in the w / c ratio and an increase in the cement stone's strength was obtained. High-strength cement composites have been obtained with the optimal content of the complex additive. The volume-weighted average crystallite sizes were calculated using the Scherrer formula on the basis of X-ray studies. Deformation diagrams of statically loaded samples of prisms of the basic and control compositions of high-strength concrete were obtained. Deformation diagrams are investigated.

Composite and Metal Structural Elements Joint Strength

The paper reveals the hybrid structure strength studies results, which consists of composite and metal parts. The object of the study was an experimental transmission shaft of an aircraft high-lift system. It consisted of a composite tube and metal flanges. New high-strength composites, modern metal powders and additive technology were used for its manufacture. This is the feature that differ the shaft from the typical metal structures used at present. The shaft strength investigation included static tests and calculations. During the tests, the maximum torque and the corresponding shaft twist angle were determined. Based on the computational analysis results, the critical stresses and reserve factors of its structural elements were calculated. The assessment of the effectiveness of the new technologies application for joining structural elements using discrete pins was carried out.

High strength composites of carbon fiber sheets-veneers sandwich-structure for electromagnetic interference shielding materials

Due to the advantages of porous structure, anisotropy, and fiber composition, wood possesses great potential to be a high-strength electromagnetic interference (EMI) shielding material. This study used vacuum assisted resin transfer molding (VARTM) technology to fabricate EMI shielding composite material by combining carbon fiber sheets and wood veneers via infusion of epoxy resin. The shielding effectiveness of the composites against electromagnetic waves in the 8.2–12.4 GHz (X-band) can reach 40 dB. The flexural and tensile strength (i.e., 442.3 and 195.5 MPa, respectively) of the composite were 6-fold and 3-fold higher than natural poplar (i.e., 69.8 and 55.6 MPa, respectively), respectively. The composites possessed superior thermal conductivity (0.91 W m-1 K-1) compared to poplar, good water resistance and surface hydrophobicity. The addition of carbon fiber sheets not only improved the mechanical performance of samples, but also made samples possessing the ability to shielding electromagnetic waves. This work provides a novel technology to make a natural bio-based high-strength composite material for the EMI shielding applications.

Biomimetic architectured Kevlar/polyimide composites with ultra-light, superior anti-compressive and flame-retardant properties

Lightweight, high strength, and flame-retardant properties are highly required for practical applications of composites, such as in areas of aerospace, aircraft, and automobiles. However, it is challenging to achieve the above properties simultaneously due to the intrinsic conflict between lightweight and excellent mechanical performance. Herein, we overcome this conflict in a 3D Kevlar/polyimide composite (K/PIC) innovatively by mimicking the structural features of the beetle's elytra. As a result, the K/PIC has a void content of 84% and a low volume density of 0.23 g/cm3, but it can support more than 16 000 times its own weight without any damage. It exhibits a specific strength of 23.5 MPa/g·cm−3, which is superior to that of many other reported lightweight composites. Additionally, the as-prepared K/PIC could not be ignited and could retain around 93.2% of its original compressive strength even after being subjected to the flame of an alcohol burner for 300 s. The results demonstrate that similar lightweight, high strength, and flame-retardant composites can be fabricated by this underlying principle in future and be applied in extreme environments, such as aeronautics and aerospace.

Configuration of new fiber-like structure driven high matching of strength-ductility in TiB reinforced titanium matrix composites

To fulfill the combination of high strength and ductility, configuration of novel fiber-like structural TiB reinforced titanium matrix composites was designed and successfully fabricated through series of powder metallurgy and hot working process. The influence of the fiber-like structure and microstructures on the mechanical response is investigated to clarify their strengthening and plasticizing mechanisms. Smaller equiaxed α-Ti grains generated in both the composites region and Ti region of the TiB/Ti composites. The new configuration improved the tensile strength from 573.5 MPa to 659.1 MPa while the ductility (24.4%) was comparable with that of pure Ti (23.5%). Besides, prismatic <a> slips with Schmid factors above 0.4 had higher distribution in both the composites region and Ti region of the TiB/Ti composites than pure Ti along the loading direction, suggesting the higher deformation ability of the TiB/Ti composites. Moreover, the loading-unloading-reloading (LUR) true stress-strain curves showed much higher back stress in fiber-like structural TiB/Ti composites compared with unreinforced Ti during deformation. The existence of the back stress increased the strain hardening rate when the true strain was above 0.05 and strengthened the Ti region, which was caused by deformation incompatible between the composites region and Ti region during tensile loading in the TiB/Ti composites. The higher mechanical response of the TiB/Ti composites is attributed to the introduction of TiB reinforcements with the new fiber-like structure, and the coupling effect of consequent grain refinement, load transferring effect, dislocation pinning effect of the fine TiB particles, back stress strengthening and the higher Schmid factors of prismatic<a> slips. • Novel fiber-like structure was designed to match the high strength and ductility in TMCs. • Configuration design of high strength composites without losing ductility by tailoring the spatial distribution of reinforcements. • The ductility of the composites was maintained for the higher Schmid factor values of prismatic<a> system and back stress. • Grain refinement, load transferring effect and back stress strengthening result to the strength improvement.

Modeling Flexural Failure in Carbon-Fiber-Reinforced Polymer Composites

Flexural testing provides a rapid and straightforward assessment of fiber-reinforced composites’ performance. In many high-strength composites, flexural strength is higher than compressive strength. A finite-element model was developed to better understand this improvement in load-bearing capability and to predict the flexural strength of three different carbon-fiber-reinforced polymer composite systems. The model is validated against publicly available experimental data and verified using theory. Different failure criteria are evaluated with respect to their ability to predict the strength of composites under flexural loading. The Tsai–Wu criterion best explains the experimental data. An expansion in compressive stress limit for all three systems was observed and is explained by the compression from the loading roller and Poisson’s effects.

High strength composites from low-value animal coproducts and industrial waste sulfur.

Herein we report high strength composites prepared by reaction of sulfur, plant oils (either canola oil or sunflower oil) and brown grease. Brown grease is a high-volume, low value animal fat rendering coproduct that represents one of the most underutilized products of agricultural animal processing. Chemically, brown grease is primarily comprised of triglycerides and fatty acids. The inverse vulcanization of the unsaturated units in triglycerides/fatty acids upon their reaction with sulfur yields CanBGx or SunBGx (x = wt% sulfur, varied from 85–90%). These composites were characterized by infrared spectroscopy, dynamic mechanical analysis (DMA), mechanical test stand analysis, elemental analysis, and powder X-ray diffraction. CanBGx and SunBGx composites exhibit impressive compressive strengths (28.7–35.9 MPa) when compared to other materials such as Portland cement, for which a compressive strength of ≥17 MPa is required for residential building. Stress–strain analysis revealed high flexural strengths of 6.5–8.5 MPa for CanBGx and SunBGx composites as well, again exceeding the range of ∼2–5 MPa for ordinary Portland cements. The thermal properties of the composites were assessed by thermogravimetric analysis, revealing decomposition temperatures ranging from 223–226 °C, and by differential scanning calorimetry. These composites represent a promising new application for low value animal coproducts having limited value to be used as organic crosslinkers in the atom-efficient inverse vulcanization process to yield high sulfur-content materials that have impressive mechanical properties.

Processing pulp fiber into high strength composites

ABSTRACT The mechanical performance of wood fibre-based panels is unsatisfactory for many advanced engineering structures and applications; it also releases free formaldehyde. Here, we report a simple and effective strategy to transform wood fiber (pulp fiber) into high strength composite panels without adhesive bonding. Our two-step process involves layer by layer self-assembly of bleached cellulose mixed with microcrystalline cellulose (MCC) and dibasic calcium phosphate (DCP). This was followed by hot-pressing, leading to the complete densification of the wood pulp fiber with highly aligned cellulose nanofibers. The result showed that the flexural and tensile strength could reach up to 147MPa and 58 MPa, respectively, which are much stronger than those of existing types of wood fiberboard, mainly resulting from the synergistic effects of hydrogen bonding and ionic bonding between the pulp fibers and DCP sheets.

X-ray diffraction of concrete composites of high structural strength and density

Аn analysis of the structure formation of concrete composites, compressive strength of which exceeds 120 MPa and a quantitative analysis of their qualitative composition and hydration products by X-ray diffraction, x-ray spectral analysis. The main factors affecting the physicomechanical parameters of the complex of various nanofillers and the formation of a denser cement stone structure, which mainly includes calcium hydrosilicates, calcium silicate hydroaluminates and hydroaluminates of various basicity, are studied.

3D-printing of architectured short carbon fiber-geopolymer composite

Developing advanced lightweight structures with both high strength and high toughness remains challenging. Herein, we provide a combined experimental and simulation method to fabricate 3D-printed geopolymer complex structures with lightweight, high strength and superior toughness for the first time. In this research, short carbon fiber reinforced geopolymer (C sf GP) composites were printed using 3D printing technology, and the rheological properties of C sf GP inks and the mechanical properties of hardened geopolymer composite structures were systematically studied. The C sf GP inks exhibited obvious shear-thinning behavior, which facilitated ink-extrusion from a micro-nozzle, conserving the filamentary shape and supporting the subsequent printed layers. In C sf GP composites, the consistent orientation distribution of short carbon fibers primarily enhanced their mechanical properties. When fiber content was 3 wt %, flexural strength and compressive strength of the C sf GP composite were 309.2% and 375.8% higher than those of nonreinforced geopolymer, respectively. Subsequently, C sf GP composites of the Bouligand architectures were successfully 3D-printed, and they showed superior load-bearing capacity and non-brittle failure mode due to their hierarchically ordered architectures and sophisticated interfaces. 3D printing together with Bouligand-structure designing provide a novel approach for the C sf GP composites of lightweight, high strength and superior toughness, which would lead to a resurgence of interest in new lightweight structure design and manufacturing strategies. • Short carbon fiber reinforced geopolymer (C sf GP) inks were 3D printed by direct ink writing. • Consistent fiber orientation distribution was achieved in the printed C sf GP composites. • C sf GP of Bouligand structures were designed and printed, and the fracture behavior of these structures was investigated. • The obtained C sf GP of Bouligand structures showed light-weight, high strength and superior toughness, and non-brittle failure behavior.

Effect of Functionalized Multi-Walled Carbon Nanotubes on Preparation of High Strength and Conductive Copper-CNTs Composites by Electrodeposition

Functionalized multiwalled carbon nanotubes (MWCNTs)-reinforced copper (Cu) composites were prepared by the combination of electrowinning and hot-pressing sintering and cold rolling process. The influence of the functionalization of MWCNTs on the strength and electrical properties of MWCNTs/Cu composites was studied. Functional group was introduced to increase the wetting of water electrolytes, improve the poor wettability of MWCNTs and form a highly active surface suitable for the preparation of MWCNTs/Cu composites by electro-deposition, enabling MWCNTs to be evenly dispersed in Cu matrix. Studies have shown that the addition of 1% of functionalized MWCNTs composite can increase the tensile strength by 6% and 165% compared with the addition of unfunctionalized and pure copper. It’s worth noting that the increase of oxygen-containing functional group brought about by functionalized MWCNTs did not significantly reduce the electrical properties of composites. The main reason for this is the good dispersion of the treated MWCNTs in Cu matrix and the bridging for electronic transmission, ensuring that the high electrical properties of MWCNTs/Cu composites are just slightly lower than those of electrolytic pure copper (99.92% IACS).

Resistance of hybrid layered composite panels composed of fiber-reinforced cementitious composites against high-velocity projectile impact

The purpose of this study is to present an experimental investigation of the impact resistance of hybrid layered panels composed of high-strength fiber-reinforced composite and high-ductility fiber-reinforced composite. Seven types of panels were prepared with three types of composites and hybrid use of composites. A series of experiments including static loading tests and high-velocity projectile impact load tests was performed. From the test results, it was found that the hybrid layered panels, in which a high-strength composite was located at the front side and a high-ductility composite was located at the rear side, had impact resistance higher than those of other panels. It was also observed that the hybrid layered panels showed different damage patterns than those of the panels made of single material.

Effect of the Segmental Structure of Thermoplastic Polyurethane (Hardness) on the Interfacial Adhesion of Textile-Grade Carbon Fiber Composites

In polymer composites, the fiber–matrix interface is primarily influenced by the surface treatment of the fibers and polymer morphology. Previous studies have investigated the effect of surface treatment of carbon fiber on the mechanical properties of the resulting composites. However, very few studies have explored the chemical structural modification of polymer effect on the fiber–matrix adhesion. In this work, the interfaces of soft thermoplastic polyurethane (S-TPU) and hard-segmented TPU (H-TPU) were investigated through surface, thermal, and mechanical characterization. A textile-grade carbon fiber (TCF) with 1% concentration of epoxy sizing (an emerging material for nonaerospace applications with 450 K filament tows) was used as a reinforcement to investigate the structure–property relationship at the interface. Atomic force microscopy results showed 39% higher surface roughness for S-TPU than for H-TPU. X-ray photoelectron spectroscopy results revealed a 550% increase in C═O content, which can provide multiple hydrogen bonding networks in H-TPU, and these C═O bonds can produce a strong chemical bond at the fiber–matrix interface. Dynamic mechanical analysis and differential scanning calorimetry results confirmed the presence of hydrogen bonding that enhances the cross-linked density by 232% in H-TPU compared to S-TPU. The improved mechanical properties of H-TPU composites, such as flexural, impact and tensile by 30, 50, and 130% compared to S-TPU composites, prove that the crystallinity and hydrogen bonding significantly increase the load bearing capacity due to the strong interface. The mechanical properties of TCF–TPU composites validate the formation of chemical bonds through a nucleophilic addition reaction at the interface and improve the bond strength of the composites. Thus, tailoring the polyurethane structure broadens the performance of segmented TPU in conjunction with TCF reinforcement, which has implications for cost-effective, high-strength composites.

Environmental remediation potentialities of metal and metal oxide nanoparticles: Mechanistic biosynthesis, influencing factors, and application standpoint

Nanotechnology has emerged as a promising field in the development and modification of new nanostructured materials for multifaceted applications, including environmental remediation. Nanoparticles based trendy materials as robust adsorbents and efficient catalytic constructs offer unique structural, chemical, and multifunctional properties, such as high mechanical strength, morphologies, and diverse composition, which promise its use in catalysis, adsorption, degradation, and so on. Herein, we report contemporary advances in metal and metal oxide nanoparticles and their strategic role in environmental approaches, mainly due to the great interest and need for scientific community. The concept of green nanoscience is a practical application of advanced nanotechnology and, therefore, following this relationship between nanotechnology and green chemistry, the biosynthesis of nanoparticles has evolved as an excellent approach. In view of the different techniques widely explored for nanoparticles synthesis, it is possible to state that the main methods currently used are expensive, environmentally harmful, and inefficient regarding the use of materials with applications viewpoints. The natural extracts contain several secondary metabolites that assist in the redox process of metal ions in nanoparticles. Special attention is given to synthetic biological procedures and solvent systems when compared to nanoparticles obtained by non-biological methods. Here, we review recent advances in mechanistic approaches to nanoparticle biosynthesis, as well as the parameters influencing production rate, size, morphology, and their environmental implications. It will become evident that the environmental implication is a rapidly growing field. • The mechanism and factors affecting biosynthesis of metal and metal oxide nanoparticles are discussed in detail. • Biomass acts as reducing and stabilizing molecules in biosynthesis. • Physical chemistry techniques to characterize nanoparticles are outlined. • Environmental remediation potentialities of biosynthesized nanoparticles.

Application of the C-S-H Phase Nucleating Agents to Improve the Performance of Sustainable Concrete Composites Containing Fly Ash for Use in the Precast Concrete Industry.

Siliceous fly ash (FA) is the main additive to currently produced concretes. The utilization of this industrial waste carries an evident pro-ecological factor. In addition, such actions have a positive effect on the structure and mechanical parameters of mature concrete. Unfortunately, the problem of using FA as a Portland cement replacement is that it significantly reduces the performance of concretes in the early stages of their curing. This limits the possibility of using this type of concrete, e.g., in prefabrication, where it is required to obtain high-strength composites after short periods of curing. In order to minimize these negative effects, this research was undertaken to increase the early strength of concretes with FA through the application of a specifically formulated chemical nano-admixture (NA) in the form of seeds of the C-S-H phase. The NA was used to accelerate the strength growth in concretes. Therefore, this paper presents results of tests of modified concretes both with the addition of FA and with innovative NA. The analyses were carried out based on the results of the macroscopic and microstructural tests in five time periods, i.e., after 4, 8, 12, 24 and 72 h. The results of tests carried out with the use of NA clearly indicate the possibility of using FA in a wide range of management areas in sustainable concrete prefabrication.

Influence of coconut shell powder on physico‐mechanical, thermal, and morphological properties of polyvinyl chloride recovered from waste rigid pipes

AbstractThis research work focuses experimentally study on the utilization of coconut shell powder (CSP) as a strengthening filler in recycled polyvinyl chloride (r‐PVC) retrieve from waste PVC pipes to high mechanical strength composites. Herewith, to improve the interaction within the organic based natural filler and un‐plasticized r‐PVC, the epoxidized soybean oil (ESO) was used as a processing aid. The melt mixing of r‐PVC using CSP as well as ESO was carried out by a two‐roll milling process and further sheets manufacturing process followed by compression molding. The effect of CSP filler content on the physico‐mechanical properties, thermal properties, and morphology of r‐PVC/CPS composites was investigated. The result shows that the incorporation of CSP filler within polymer indicated, the change in physical with enhancement in mechanical properties such as tensile strength, modulus of elasticity, impact strength, and surface hardness properties. Meanwhile, the density and water absorption of composites has been increased as the filler content in the r‐PVC matrix increases. The morphology study of composites indicates poor interfacial interaction as an increase in CSP content in the composites. The marginal improvement in thermal stability of prepared composite also increased with 20 wt% of CSP content and analyzed by performing differential scanning calorimetry, thermogravimetry analysis. This study, therefore, shows the potential of CSP filler in r‐PVC as an alternative particulate material for the development of a new polymer matrix composite.

Modified Epoxy Resins for Perpreg Technology

A curing system has been developed for obtaining high-strength compositions matrix, which is used in the production of composites based on reinforced carbon fiber using prepreg technology with a curing temperature of . A technology has been developed for combining an epoxy oligomer with a curing agent and modifier. The pot life of the prepared prepregs is at least 15 days.