Advanced Composite Applications Research Articles

Development of low temperature cure hybrid benzoxazine-epoxy resins for thermally stable and moisture resistant applications

New type of diallyl bisphenol-A (ABA) based benzoxazines and benzoxazine resins tailored with epoxy groups for low-temperature curing, have been developed using various curatives for high performance applications. The molecular structure of the synthesized compounds was analyzed using HRMS, 1H NMR, 13C NMR and ATR-FTIR analytical techniques. The cure behavior (Tp) of benzoxazine (Bz) and benz-epoxy (Bz-Ep) resin in the absence and presence of different nature of curatives were studied using DSC to evaluate their applicability for advanced composite applications. The values of Tp obtained are 279 °C, 190 °C and 247 °C for ABA-a, ABA-dmapa and ABA-ipa respectively. The cure behavior has been further lowered by converting ally group present in the benzoxazine has been transformed into epoxy groups by appropriate mechanism. The curing (Tp) temperature observed for hybrid ABA-a-Ep, ABA-dmapa-Ep and ABA-ipa-Ep benz-epoxy resins are 151 °C, 226 °C and 160 °C, 187 °C and 150 °C, 211 °C respectively. The Tp of different benz-epoxy resin systems studied in the presence of catalysts were found to be in the range of 101-155 °C. With a Tmax of 484 °C and a char yield of 43 %, poly(ABA-a) exhibits impressive thermal stability when compared to other synthesized polybenzoxazines. Further, incorporating various curatives into the benz-epoxy matrix enhances its thermal stability and char yield compared to the neat matrices. Additionally, the developed samples exhibit excellent moisture resistant (0.75 %) and hydrophobic nature with the highest contact angle value of 152o for poly(ABA-a). The findings from various studies indicate that the hybrid benz-epoxy resins demonstrate characteristics such as low-temperature curability, thermal stability, hydrophobicity. These results render them appropriate for a diverse array of high-performance industrial and engineering uses.

Artificial Intelligence prediction and optimization of the mechanical strength of modified Natural Fibre/MWCNT polymer nanocomposite

Artificial Intelligence (AI), techniques like artificial neural networks (ANN), and machine learning have been used to solve a variety of engineering problems. In this study, Multiwall Carbon Nanotube (MWCNT) and Natural Fibres (NF) from plantain (Musa Paradisiaca) fiber (PF), were utilized to prepare a reinforced hybrid polymer nanocomposite for advanced composite applications. A chemical solution containing potassium permanganate (KMnO4) in acetone (C3H6O) was applied to modify the fibers to alter their surface and improve adhesion and interaction between the PF/polymer matrix. To predict and optimize the tensile strength (TS) of the prepared PF/MWCNT hybrid nanocomposite (PFMNC), the ANN model with hyper-parameter optimization in a single-layer-perceptron architecture of 3-5-1 was used with 5 neurons in the hidden layer, and Box-Behnken Design (BBD) was utilized. Scanning electron microscope (SEM) micrographs demonstrate that KMnO4 modification has impacted the TS of the hybridized nanocomposite. Mechanical Test results show that these variables impacted the TS of the PFMNC as shown by analysis of variance (ANOVA) with R2 = 0.9986. The expected findings were nearly identical to the experimental results. The model predicted an optimal tensile strength of 46.1563 Mpa. To substantiate the reliability of the empirical experimental investigation, TS analysis was performed at predicted optimal settings. TS results showed an average strength of 45.4401 Mpa. About 98.45 % of the projected tensile strength is accounted for by the model. The present study has demonstrated the effectiveness of the ANN-BBD modeling technique in achieving the appropriate mechanical property values quickly, reducing production costs, and preserving resources.

Improved Thermomechanical and Viscoelasticity Properties of Bio-Epoxy/date Palm Fiber Composite by Addition of Eggshell Particles

ABSTRACT In this research, a novel eco-friendly green composite is fabricated by combining a biomatrix composed of a biopolymer, date palm fiber, and a filler obtained from discarded eggshell (ES) waste material. This research aims to check the influent of ES filler on thermal and viscoelasticity properties of bio-epoxy composite with incorporation of 40 wt.% date palm (DP) fiber. Various ES filler ratios, specifically 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.%, are dispersed into the composite. Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) approach were employed to investigate the properties of fabricated composites as a function of temperature in terms of storage modulus (E′), loss modulus (E′′), Tan delta (Tan δ), glass transition temperature (Tg), and Cole-Cole plot. Overall, incorporating ES filler into the bio-epoxy/DP fiber composites increased E′, E′′, and Tg significantly. ES-filled composites containing 5 and 10 wt.% exhibited properties comparable to 15 wt.% but less than 20 wt.% ES filler. Thermal tests result show that 20 wt.% ES-filled materials outperform their counterparts in terms of heat resistance or thermal stability. The evidence suggests that the embodiment of ES filler in bio-epoxy/DP fiber composites yields enhancements in both thermal and dynamic mechanical properties. This indicates the potential for utilizing ES filler loading in advanced composite applications that prioritize thermal stability and sustainability.

Comparison of properties of carbon reinforced plastic obtained on the basis of semicrystalline polyimideR‐BAPBand other high‐temperature‐resistant thermoplastic matrices

AbstractHeat resistant thermoplastic matrices offer potential advantages over thermoset polymers and represent a promising alternative in advanced composite applications. In the present work, the properties of carbon fiber reinforced plastics (CFRPs) based on the developed semicrystalline polyimide R‐BAPB were studied and compared with those of highly heat‐resistant thermoplastic polymers such as amorphous polyetherimide Ultem‐1000 and semicrystalline polyetherketone PEEK. To obtain CFRP, an approach was used basing on the uniform distribution of polymer powders on continuous carbon fibers by electrostatic spraying followed by their impregnation in heated calenders and hot pressing. The thermal and thermomechanical properties of CFRPs based on mentioned above polymers were studied. The effect of temperature on the mechanical behavior of CFRPs, including flexural properties and interlaminar fracture toughnessG1C, was investigated as well. CFRPs based on PEEK and R‐BAPB are found to have the highest thermal stability and heat resistance. The maximum flexural strength, which practically does not change in a wide temperature range from −50 to 180°C, is observed for CFRP based on R‐BAPB polyimide. Among the investigated CFRPs, the highest value of interlaminar fracture toughness is shown by CFRPs based on semicrystalline R‐BAPB.

Buckling and Post-buckling Analysis of Composite Hat Stiffened Panels under Axial Compression Loads

Owing to their unique material design-ability and excellent weight reduction properties of carbon fibre reinforced polymers(CFRP), commercial aircraft OEMs have been innovating design and manufacturing approaches to wider the application of advanced composites. In this paper, the bearing capacity of composite hat-stiffened panels is determined by an improved engineering calculation method and numerical analysis method. The effectiveness of both methods is verified by the test. The advantage of the engineering estimation method is simple and fast, which is suitable for the parametric analysis of the structure in the preliminary design phase. The finite element method can better simulate the test process and is suitable for the comprehensive evaluation of structural strength. The combination of the two methods has a high reference value for rapid design and selection.

Influence of Chemical Treatments on the Physical and Mechanical Properties of Furcraea Foetida Fiber for Polymer Reinforcement Applications

ABSTRACT The usage of natural fibers is regarded as the most viable solution for controlling the consumption of synthetic materials. However, the low moisture resistance, stiffness and poor adhesion capabilities restrict their use in several advanced composite applications. Hence, different surface treatments are employed to improve the physical characteristics of natural materials. In this study, the effect of chemical treatments (sodium hydroxide, acetic acid, potassium permanganate and bromodecane) on the surface characteristics and the adhesion capabilities of Furcraea foetida (FF) fiber with epoxy material is evaluated. From the study, it is seen that the chemical treatment (CT) eliminates the O-H functional groups and enhances the hydrophobic characteristics in FF fiber. Furthermore, the CT removes the amorphous organic attachments and improves the crystallinity in the fiber. However, no substantial increase in the thermal stability of FF fiber was observed post chemical treatment. The microscopic analysis of chemically treated FF (CTFF) fiber shows the elimination of organic attachments and developed neat uniform surface structure. The NaOH-treated FF fiber exhibited maximum tensile strength (σt: 241.75 MPa). Whereas the acetic acid-treated FF fiber showed maximum tensile modulus (σm: 6.9 GPa) and interfacial shear strength (IFSS: 0.06 MPa) compared to CTFF and untreated FF fiber (UTFF).

Advanced ceramics and coatings for erosion‐related applications in mineral and oil and gas production: A technical review

AbstractThe applications of advanced ceramics, composites and coatings in mineral, mining, fuel production, and processing are reviewed. The materials include oxide and non‐oxide ceramics (specifically SiC‐based), ceramic–ceramic, and ceramic–metal composites, coatings on metallic components where functional application properties can be achieved. Some principles of materials selection, specifically for erosion wear and corrosion applications, and manufacturing are considered. The examples of the successful development and processing of ceramics, coatings, and composites with manageable structures and phase compositions, in the erosion‐related applications, particularly conducted by the author, are discussed and reviewed. Specifically, industrially employed types of ceramics and processing routes were focused on the considered applications. Particular demands for advanced materials with high reliability and complex shapes or for protective coatings on complex shape steel components and long tubing with inner surface protection require novel and optimized processing. The factors affecting erosion and erosion–corrosion resistance and the paths for the erosion resistance enhancement of ceramic and coating materials are considered. Ceramic components design, technology, and installation features are reviewed.

Multifunctional Characteristics of Carbon Fibers Modified with Imidazolium Ionic Liquids.

A multifunctional designing approach is of great importance for advanced composite applications. This study assessed the use of ionic liquids (ILs) to modify the surface of carbon fiber (CF) and impart multifunctional characteristics to it. For that, ethanolic solutions of different ILs, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium chloride and 1-(2-hydroxyethyl)-3-methylimidazolium chloride, at different concentrations, were used to treat the CF. Fourier-transform infrared spectroscopy confirmed the presence of IL on the CF surface. The contact angle for 1% w/v IL-treated CF and DGEBA epoxy decreased by up to 35%, corresponding to an increase in surface energy of fiber, accompanied by an increase of 91% in interfacial shear strength. These enhancements were achieved with the hydroxy-functionalized IL, showing the tunability of CF properties through the N-imidazolium substituent. An increase in crystallite size along the basal plane was also found due to the ordering of the graphitic structure on the surface. Moreover, there was a decrease in electrical resistivity of 77%. In all, the imidazolium ILs were considered a promising approach to induce multifunctional characteristics, namely enhanced interfacial strength and electrical conductivity, to unsized CF, which can also be beneficial for recycled fibers without deteriorating their inherent surface properties.

Ultrahigh strength and modulus of polyimide-carbon nanotube based carbon and graphitic fibers with superior electrical and thermal conductivities for advanced composite applications

Development of carbon fibers (CFs) with high strength and high modulus for structural applications in CF-reinforced polymer (CFRP) industry has been a challenge. Herein, we propose a method for manufacturing highly oriented polymer–carbon nanotube (CNT) composite fibers having high strength (4.8 ± 0.2 GPa), modulus (390 ± 48 GPa), and electrical conductivity (5.75 ± 0.84 MS m-1) by a liquid crystalline wet-spinning process. The use of chlorosulfonic acid (CSA) as a solvent for CNTs and polyimide (PI) promotes dispersion and enables the production of high-performance composite fibers. In addition, the functional groups of PI in composite fibers improve the interfacial shear strength with epoxy resin without sizing additives by 72% compared to that of CNT fibers. Carbonization and graphitization of the composite fibers with an optimal ratio of PI (30%) and CNT cause significant improvement in their mechanical (tensile strength; 6.21 ± 0.3 GPa and modulus; 701 ± 47 GPa) and thermal properties (496 ± 38 W m−1 K−1) by reducing voids and improving orientation. We believe that the polymer–CNT composites and their CFs with high strength and high modulus would be the next-generation CFs for aerospace and defense industry.

Special Issue: “Physics and Mechanics of New Materials and Their Applications”

Solid-state physics, directed to the design, manufacture, research, and further application of advanced materials and composites, play one of the most important roles in the quick development of modern science, techniques, and technologies [...]

Aliphatic chains grafted cellulose nanocrystals with core-corona structures for efficient toughening of PLA composites

To promote the replacement of nondegradable petrochemical-based polymers with green polylactic acid (PLA) materials, aliphatic chains-grafted cellulose nanocrystals (ECNCs) were prepared and used as nanofillers to overcome the disadvantage of poor toughness of PLA. ECNCs with core-corona structures were obtained by modifying cellulose nanocrystals (CNC) with valeryl chloride, octanoyl chloride, dodecanoyl chloride, and stearoyl chloride. ECNCs consists of a cellulose crystalline core and a soft esterified corona layer with aliphatic chains. Among the diverse ECNCs, the obtained EOCNC by esterification of octanoyl chloride exhibited most efficient enhancement of the toughness of PLA. Specifically, PLA/EOCNC-1% film displayed the best elongation at breakage of 108%, which was 6.4 times that of pure PLA. The esterified outer layer of ECNCs, which improves the interfacial compatibility, is one of the key factors contributing to toughening of PLA. These ECNCs with core-corona structure open up new directions for the application of PLA advanced composites.

Tough poly(ethylene glycol)-sized bacterial cellulose sheet for high impact strength laminated acrylic composites

Dried and well-consolidated sheet of bacterial cellulose (BC) nanofibrils is a material structure that possesses high modulus and strength but is also brittle, which limits its potential in various advanced composite applications. Here, we report a simple method of enhancing the toughness of BC sheet by sizing the BC nanofibrils with poly(ethylene glycol) (PEG). This hinders interfibril hornification and facilitates large-scale BC nanofibril debonding, slippage and reorientation upon deformation. The PEG-sized BC sheets show high tensile strain-at-failure and work of fracture compared to neat BC sheet. PEG-sized BC reinforced laminated acrylic composites achieve a flatwise Charpy impact strength of up to 26 kJ m−2. This is a remarkable increase over the impact strength of neat impact-modified acrylic of only 12 kJ m−2, especially when the BC loading required to achieve this radical improvement is only 0.2 wt-%. Our study opens new paradigm in using low BC loading to achieve performance improvements suitable for high value composite applications.

Low‐cost carbon black‐loaded functional films for interlaminar toughening and in‐situ delamination monitoring of carbon fiber/epoxy composites

AbstractFunctional polyethersulfone (PES)/carbon black (CB) films were fabricated and interleaved into carbon fiber/epoxy composite laminates to simultaneously improve the mode I interlaminar fracture toughness (GIC) and delamination monitoring sensitivity. It was found that when the CB content in the functional film was 7.5 wt%, the initial and propagation GIC of the laminate achieved the greatest improvements of 99.16% and 82.83%, respectively. The toughening mechanism was mainly attributed to the formation of phase separation structure, the plastic deformation of PES and the pull‐out of epoxy and CBs. Meanwhile, a delamination increment‐resistance change relationship equation was proposed to predict the delamination increment of the laminate during mode I delamination. Moreover, the effect of CB content in the film on the delamination monitoring sensitivity was investigated. The pure PES film showed the largest sensitivity coefficient k of 4.55, which was much higher than that of Control (0.14). When the CB content was in the range of 2.5–7.5 wt%, both GIC and k remained at relatively high levels, indicating that PES/CB films have promising applications in advanced multifunctional composites due to their low cost, simple manufacturing process, and large‐scale industrial manufacturability.

Bio-Inspired Hierarchical Carbon Nanotube Yarn with Ester Bond Cross-Linkages towards High Conductivity for Multifunctional Applications

The cross-linked hierarchical structure in biological systems provides insight into the development of innovative material structures. Specifically, the sarcoplasmic reticulum muscle is able to transmit electrical impulses in skeletal muscle due to its cross-linked hierarchical tubular cell structure. Inspired by the cross-linked tubular cell structure, we designed and built chemical cross-links between the carbon nanotubes within the carbon nanotube yarn (CNT yarn) structure by an esterification reaction. Consequently, compared with the pristine CNT yarn, its electrical conductivity dramatically enhanced 348%, from 557 S/cm to 1950 S/cm. Furthermore, when applied with three voltages, the electro-thermal temperature of esterified CNT yarn reached 261 °C, much higher than that of pristine CNT yarn (175 °C). In addition, the esterified CNT yarn exhibits a linear and stable piezo-resistive response, with a 158% enhanced gauge factor (the ratio of electrical resistance changing to strain change ~1.9). The superconductivity, flexibility, and stable sensitivity of the esterified flexible CNT yarn demonstrate its great potential in the applications of intelligent devices, smart clothing, or other advanced composites.

Engineering Advanced Composite Materials Using Liquid Crystals: From Device Application to Unconventional Cosmetics

Mixing two individually well-known materials is an established route to engineering composites with tailored properties. Such composite materials, namely those based on liquid crystals, offer the possibility of exploring phase behaviors in condensed soft matter, leading to exotic phenomena and technological innovations. This contribution reviews the design and application of advanced liquid crystal-based composites, which show emergent and intriguing properties that stem from interactions with strong magnetic fields or confinement in condensed polymer systems. This review should be of interest to academics and industries interested in magneto-responsive materials, non-volatile memory, and innovative approaches to protect and beautify the skin.

Triphenylene containing blue-light emitting semi-fluorinated aryl ether polymers with excellent thermal and photostability

Integration of polycyclic aromatic hydrocarbon (PAH) units into semi-fluorinated polymers affords high thermal stability and excellent processability for potential applications in optoelectronic, gas-separation, and advanced composites.

Conductive V2C MXene and paralelectric SrTiO3 containing polymer composites with high dielectric constant

Strontium titanate (STO) is a ferroelectric ceramic that shows paraelectric behaviour at room temperature, leading to a low dielectric constant in polymer composites with STO particles for energy storage applications. In this study, to improve the dielectric constant of polymer/STO composites, STO filler was modified via its hybridisation with conductive V2C MXene to form high-polarity interphase. The high-polarity mechanism of the V2C/STO interphase was analysed using density functional theory (DFT) calculations. An interesting connection between V2C and STO through an interfacial single oxygen atom was observed. Polymer composites containing hybrid filler exhibited balanced electrical properties, including a high dielectric constant, low tanδ, and high breakdown strength. The novelty of this study lies in the strategy of improving the dielectric response of a paraelectric ceramic filler through heterojunction modification. Consequently, the composite with 9 wt% hybrid filler exhibited a high dielectric constant of ~87 and low tanδ of ~0.038 at 100 Hz along with a reasonably high breakdown strength of ~233 MV/m. It is expected that this study will contribute to the effective design of high-polarity hybrid ceramic fillers for advanced composite dielectric applications.

Multi-functional fluorescence cellulose composites based on a modified amphiphilic waterborne polyurethane by covalent suspension of the triazine groups

Multi-functional fluorescent composites with maximal fluorescence emission are desirable in advanced materials and composites. We synthesized an amphiphilic fluorescent waterborne polyurethane (WPU) by covalent linking of a naphthalimide fluorophore (NF) containing a monochlorotriazine group. The synergy of the NF and triazine group improved absorption in the A- and B-range ultraviolet (UV). We obtained corresponding fluorescent cellulose composites by coating a cellulose matrix with modified amphiphilic WPU. We measured the fluorescence intensity and fluorescence quantum yield of modified WPU emulsions and films that contained various proportions of NF. In accordance with increasing proportion of NF in the WPU–NF, the emission peak exhibited a gradual bathochromic shift and the fluorescence intensity considerably increased. Compared with a physical blend of WPU and NF, covalent linking greatly enhanced the fluorescence intensity and fluorescence quantum yield of WPU–NF films. When the proportion of the fluorescent group was 0.200% and 0.400% (w/w), the fluorescence intensities of the covalently cross-linked polymer were 4.29× and 7.27× higher, respectively, than those of the physically mixed polymers. The cellulose composites exhibited excellent fluorescence and good UV protection. The monochlorotriazine formed covalent bonds with the cellulose matrix and in so doing improved the bonding stability. Our amphiphilic fluorescent polyurethane polymer and fluorescent cellulose composites have great potential for applications in advanced composites, biomaterials, and UV protection materials.

Design and testing of polar-orthotropic multi-layered composites under rotational load

The growing requirements for efficient and reliable high-performance rotors have led to an increased application of advanced fiber-reinforced composites. For an efficient feasibility analysis, analytical calculation methods for composite structures can provide a first design draft of typical composite components without cumbersome finite element models to engineers having low experience with anisotropic materials. In these investigations, an analytical solution for polar-orthotropic multi-layered composite rotors under rotational load is presented by transferring the well-known formulation of the classical laminate theory given in Cartesian coordinates into a formulation given in a polar coordinate system taking into consideration of centrifugal loads. The analytical results are verified under different rotational speeds with standard finite element solutions and also with experimental results at selected positions from strain gauges and diffraction grating strain sensors. The results show the usefulness of analytical solutions for the design engineer and can be further expanded to take into consideration temperature and shrinkage effects.

Welding and reprocessing of disulfide‐containing thermoset epoxy resin exhibiting behavior reminiscent of a thermoplastic

AbstractThermoset resins generally lack the ability to be welded or reprocessed like thermoplastics because of their cross‐links. Increasing use of fiber‐reinforced composites in large structures, such as rail and aircraft parts, as well as wind blades, calls for better ways to repair damages and be compliant with recycling and environmental regulations. In this article, an epoxy resin containing disulfide bonds was prepared and characterized by Fourier transform infrared, 1H‐NMR, and 13C‐NMR. The dynamic nature of the disulfide bonds allowed the cured epoxy resin to be welded like thermoplastics, and the welded joints had strength that matched the resin's cohesive strength. It could also be reprocessed with 90% tensile strength retention after three reprocessing cycles, allowing the parts to be repaired instead of being replaced. In addition, the cured resin was chemically degradable in a thiol‐based solvent, allowing it to be recycled in closed‐loop processes. Moreover, the cured epoxy resin showed a glass transition temperature of 116°C, demonstrating its potential for advanced composite applications.