Mechanical Properties Of Composites Research Articles

Strength-plasticity synergetic CF/PEEK composites obtained by adjusting melt flow rate

Short carbon fiber reinforced PEEK (CF/PEEK) composite materials with the advantages of excellent mechanical properties and easy processing, have been widely applied in the fields of aeronautics and astronautics, automotive engineering, and so on. However, their development in microinjection molding is hindered by the incompatibility between excellent plasticity and high mechanical properties. Herein, strength-plasticity synergetic CF/PEEK composites are prepared by adjusting the melt fluidity and crystallization behaviors, based on PEEK with different melt flow rate (MFR) and T800 carbon fiber. The rheological results showed that the melt viscosity of CF/PEEK composite was negatively related to the MFR of PEEK. Moreover, the mechanical properties of composites were increased by the crystallinity of PEEKs with high MFR. This work presents strength-plasticity synergetic CF/PEEK composites suitable for microinjection molding thin-walled and intricate components, offering new opportunities for next-generation portable electronic.

Polyamide 6/carbon fibre composite: An investigation of carbon fibre modifying pathways for improving mechanical properties

Carbon fibre-reinforced polyamide 6 (PA6) composites exhibit exceptional mechanical properties, making them a highly attractive material option for various industries. Their ability to combine the advantages of carbon fibres with the versatility of PA6 provides opportunities for lightweight, high-performance applications. This work presented the fabrication of a PA6/carbon fibre composition with carbon fibre was modified by two different chemicals: nitric acid and diglycidil ether bisphenol A (DGEBA). The tensile strength at break, flexural strength, Rockwell hardness and Izod impact were measured to compare the mechanical properties of composites based on the PA6 matrix with two different modified carbon fibres. The morphology of PA6-based composite with different modified carbon fibres was observed by scanning electron microscopy. The results showed that PA6 is more compatible with acid-modified carbon fibre than DGEBA-modified carbon fibre and unmodified carbon fibre. In comparison to composite materials containing unmodified carbon fibre and DGEBA-modified carbon fibre, composite containing acid-modified carbon fibre increase tensile strength (16–38% and 7–15%, respectively), flexural strength (18–66% and 51–70%, respectively), Izod impact (23–65% and 32–78%, respectively) and Rockwell hardness (50–400% and equivalence, respectively).

An efficient viscoelastic multiscale model for investigation on the cure‐induced microscopic residual stresses of composite laminates

AbstractThe cure‐induced residual stresses have a significant influence on the deformation and mechanical properties of composites. Moreover, the cure‐induced residual stresses exhibit multi‐level and multiscale distributions due to the complexity of micro‐structure of composites and anisotropic characteristics. In this paper, a computationally efficient multiscale procedure is proposed to predict the microscopic residual stresses induced by cure temperature, cure shrinkage and macroscopic residual stresses, which is based to the linear viscoelastic theory combined with the micro‐mechanics method. The instantaneous microscopic residual stresses are expressed as a linear combination of the instantaneous temperature increment, degree of cure increment and macroscopic strain increment at all times of the cure process until to the current time. The proposed method is verified in comparison with the published results in literature and the microscale FEA at different length scales, respectively. The results show that the proposed method is about a thousand times faster than directly using FEA in the microscale RVE model once the influence coefficient matrices are determined. At length, the microscale stresses of all nodes of the entire macroscale model are examined by using the proposed method. It is found that the thermal‐chemical‐mechanical loads lead to serious microscopic stresses for the matrix and interphase constituents, especially for those due to the macroscopic residual stresses.Highlights Microscale residual stress is written as a linear combination of macroscale loads. Applying macroscale loads on microscale FEA model to obtain influence matrices. The presented model avoids repeatedly FEA microscopic to improve the efficiency. The online time required for the proposed model is much less than microscale FEA. The microscale stress increases the risk of matrix cracking and interface bonding.

The influence of in situ microfibrillation on the mechanical properties and warpage of low‐density polyethylene/polystyrene composite prepared by fused filament fabrication

AbstractFused filament fabrication (FFF) has been widely adopted due to its simplicity and cost‐effectiveness. But until now, its application materials are still limited. Polyolefin material is one of the most commonly used plastics. However, low‐density polyethylene (LDPE) is rarely used in FFF due to the inadequate strength of the filaments and the warpage of the printed parts. In this work, polystyrene (PS) is added to LDPE to obtain blend filaments. After that, the filaments are used to validate the possibility of in situ microfibrillation directly in the process. The results show that the addition of PS can significantly improve the bending strength, bending modulus, and hardness without affecting the heat resistance and crystal transition of the composite. Besides, the PS dispersed phase can form microfibers under the influence of the shear field. The formation of microfibers can significantly enhance the mechanical properties of composites. The tensile strength and Young's modulus increase by 140% and 221%, respectively. The warping deformation and surface morphology of printed parts are also improved. This study provides a new idea for utilizing low‐strength polyolefin in 3D printing and achieving performance enhancement.

Multiscale enhancement of carbon/carbon composite performance by self-assembly of sulfonated graphene with silane-treated carbon fibers

The application prospects of carbon/carbon composites are greatly limited by interfacial cracks and pores caused by binder pitch displacement and cracking during high-temperature carbonization. In this study, silane coupling agent was coated on the surface of oxygen plasma-treated carbon fibers (CFs) and subsequently electrostatically self-assembled with sulfonated graphene (SG) to improve the interfacial bonding between filler and CTP. The results indicate that the tensile strength of carbon fiber treated with silane coupling agent increased by 19 % compared to untreated CF. This increase in strength may be related to the layer of silane coupling agent that repaired the grooves and imperfections on the CF surface. The addition of SG not only improves the distribution characteristics of the fibers, allowing the silane-treated CF to play a greater role in the matrix, but also creates a three-dimensional hydrogen-bonded cross-linking between the SG and the coal tar pitch (CTP) on the surface of the fibers. This inhibits CTP displacement and pyrolysis, achieving a tight bonding of the fiber to the matrix. The composites' structural integrity and mechanical properties were significantly improved due to the synergistic effect of silane-treated CF and SG. The compressive strength was 216.98 MPa, with a flexural strength of 54.78 MPa, 250 % higher than the untreated carbon fiber-reinforced composites. Additionally, the porosity decreased by 31.5 %, and the antioxidant properties increased. The study presents a potential solution to improve the performance of carbon/carbon composites by using the silane-treated CF-SG multiscale reinforced phase.

Effects of Nanoparticles on the Mechanical Properties of the Composites Prepared from Biological and Chemical Gels

Poly (N-isopropyl acrylamide) (PNIPAm) and polyacrylamide (PAAm) are widely used in antifouling research because of their non-harmful nature and their high water-absorbing capacity. In addition, hydrogels such as these two, should be investigated for their mechanical properties because their mechanical properties influence the antifouling paint containing them remaining on the surface of the vessels. In this research PAAm, PNIPAm, and kappa carrageenan (κC) doped with graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) composite gels were examined for their mechanical properties for use in antifouling paints as a potential material. For increasing the mechanical properties of composites, GO and MWCNTs are often used as doping materials. In the research described here, a compressive test was used to determine the elasticity, and the modulus was calculated. The toughness was calculated from the slope of the stress-strain curve. The PAAm, PNIPAm, and κC doped with GO and MWCNT exhibited excellent swelling and deswelling behavior and good mechanical properties as composites. The results showed that the composites’ mechanical characteristics increased with an ideal loading concentration of GO and MWCNTs. This study was inspired by our belief of a shortage of research on antifouling materials that are sensitive to the environment. We wanted to create materials that were both effective against fouling and environmentally safe by integrating the beneficial characteristics of hydrogels with potential materials inside antifouling paint. This study, we suggest, is an important step toward the development of antifouling materials with high mechanical performance that are also environmentally friendly.

Enhanced interfacial, mechanical, and anti-hygrothermal properties of carbon fiber/cyanate ester composites with the catalytic sizing agents of titanium epoxy

The mechanical properties of composites are closely related to the interfacial behavior, especially under the hygrothermal circumstance. A catalytic sizing agent of titanium epoxy is designed to enhance interfacial, mechanical, and anti-hygrothermal properties of high modulus carbon fiber (HMCF)/cyanate ester composites simultaneously. The mechanisms of interface enhancement and low hygroscopicity of composites are investigated. The titanium epoxy is synthesized and its catalytic effect on the curing of cyanate ester is proved. The interfacial properties of HMCF composites with catalytic sizing agents are improved to 95.5 MPa, which is attributed to the interphase with high crosslinking density and sufficient triazine rings and oxazolidinone structure due to preferential curing induced by interfacial catalysis, stimulating the smooth transition of interphase modulus. Further, the formed interphase exhibits few interface defects and low content of hydroxyl groups, which changes the moisture diffusion path and reduces saturated water absorption of composites to only 0.36 %, resulting in the release of interfacial wet stress concentration and high retention of mechanical properties in hygrothermal environment. The resultant composites with high stiffness, excellent temperature resistance, superior dimensional stability and low moisture absorption are expected to be applied to high-orbit space, aerospace, precision instruments.

Mechanical properties enhancement of 3D-printed HA-PLA composites using ultrasonic vibration assistance

ABSTRACT 3D-printed HA-PLA composites have attracted much attention because of their excellent biodegradability and osteointegration properties. However, HA particles negatively affect the mechanical properties of the composite parts. In this study, ultrasonic vibration-assisted 3D printing was used to improve the mechanical properties of HA-PLA composite specimens, and the effects of different infill angles and ultrasonic vibration power on the mechanical properties were investigated. The results demonstrated that the degradation and anisotropy of the mechanical properties of HA-PLA composites were alleviated by the use of ultrasonic vibration. By applying the ultrasonic vibration, the tensile and flexural strengths of the 20 wt% HA-PLA specimens fabricated with a 90° infill angle demonstrated the largest improvement of 104.3% and 112.7%, respectively. The high-frequency ultrasonic vibration waves promoted the spreading and fusion of the extruded materials, thereby reducing overlapping voids within the specimens and improving the interface bonding strength, also facilitated the refinement and dispersibility of the HA particles, which inhibited the formation of stress concentrations within the specimens and ultimately improved the mechanical properties. The printing process developed in this study can also be adapted to other particle (or other reinforcement types) reinforced composite to improve their mechanical performance.

Matrix curing and stress field development around fiber during the solvent evaporation-induced repolymerization of recycling composites

When recycling fiber-reinforced composites using depolymerized polymer solutions, oligomers reconnect through covalent bond exchange reactions (BERs), which ultimately forms a crosslinked network with mechanical properties comparable to those of virgin materials. This process offers exciting opportunities for the primary recycling of engineering composites, but it is intricately influenced by a few material and process parameters, such as heating temperature, duration, and fiber volume fractions. These parameters collectively determine the matrix's curing degree and the evolution of stress fields around the fiber, which are significant factors determining the quality and mechanical performance of recycled composites. This study introduces a diffusion-reaction-mechanics finite-element computational model to examine the solvent-induced repolymerization process in recycling composites. The model predicts the matrix curing degree, residual stress development around the fiber, and the composite's mechanical properties, aligning with experimental results. Parametric computational studies are then conducted to assess the influences of temperature, fiber content, solvent diffusivity, and the reactivity of BERs. The objective is to identify material and processing conditions that ensure efficient composite recycling while minimizing the development of residual stress. Overall, this study enhances our understanding of the mechanisms behind composite recycling using organic solvents and provides valuable insights for industrial stakeholders looking to optimize processing conditions and advance the commercialization and widespread adoption of this innovative recycling technique.

Microstructures and mechanical properties of TiAl matrix composites with multi-precipitates quasi-continuous network reinforced structures

A novel quasi-continuous network reinforced structure that consists of borides and carbides in B4C/TiAl matrix composites was innovatively designed for the strengthening at high temperatures. Simultaneously, impacts of such reinforced structures on microstructures and mechanical properties of the composites have been unveiled. TiAl matrix units in B4C/TiAl composites are duplex microstructures which are composed of (α2+γ) colonies and γ grains. The ascent of B4C contents triggers off the formation of network reinforced structures in the layers of TiAl matrix units. With B4C contents increasing to 0.1 wt%, elasticity modulus and ultimate compressive strengths of B4C/TiAl composites are upgraded from 10.944 GPa and 723.10 MPa to 16.052 GPa and 774.611 MPa. As B4C contents reach at 5.0 wt%, elasticity modulus and ultimate compressive strengths further soar to 17.244 GPa and 799.19 MPa. Borides and carbides within the quasi-continuous network reinforced structures are unfolded as stripe and needle shaped TiB with B27 structure and Ti2AlC particles with MAX structure. Parts of Ti2AlC particles take TiB as cores to nucleate and grow. Moreover, TiC phases usually act as the cores for the nucleation of Ti2AlC particles. The orientation relationships of such reinforcements represent as [011]TiC//[010]TiB, (1–11)[011]TiC//(0006) [-2110]Ti2AlC, [100]TiB//[0001]Ti2AlC, [010]TiB//[-2110]Ti2AlC and [001]TiB//[01–10]Ti2AlC. The fractures of TiB are usually along or perpendicular to [010]TiB direction. Meanwhile, the fracture surfaces of TiB are always parallel to (100)TiB or (010)TiB planes. Additionally, dislocations slip through Ti2AlC particles and lead to separation and sliding of staking planes (0001)Ti2AlC within Ti2AlC lattices. TiB and Ti2AlC with alternative distribution can stabilize the network reinforced structures and upgrade properties of B4C/TiAl composites.

Effect of freeze‒thaw cycles on root-Soil composite mechanical properties and slope stability.

Natural disasters such as landslides often occur on soil slopes in seasonally frozen areas that undergo freeze‒thaw cycling. Ecological slope protection is an effective way to prevent such disasters. To explore the change in the mechanical properties of soil under the influence of both root reinforcement and freeze‒thaw cycles and its influence on slope stability, the Baijiabao landslide in the Three Gorges Reservoir area was taken as an example. The mechanical properties of soil under different confining pressures, vegetation coverages (VCs) and numbers of freeze‒thaw cycles were studied via mechanical tests, such as triaxial compression tests, wave velocity tests and FLAC3D simulations. The results show that the shear strength of a root-soil composite increases with increasing confining pressure and VC and decreases with increasing number of freeze‒thaw cycles. Bermuda grass roots and confining pressure jointly improve the durability of soil under freeze‒thaw conditions. However, with an increase in the number of freeze‒thaw cycles, the resistance of root reinforcement to freeze‒thaw action gradually decreases. The observed effect of freeze‒thaw cycles on soil degradation was divided into three stages: a significant decrease in strength, a slight decrease in strength and strength stability. Freeze‒thaw cycles and VC mainly affect the cohesion of the soil and have little effect on the internal friction angle. Compared with that of a bare soil slope, the safety factor of a slope covered with plants is larger, the maximum displacement of a landslide is smaller, and it is less affected by freezing and thawing. These findings can provide a reference for research on ecological slope protection technology.

Investigation of the mechanical and physical properties of mesoporous silicon dioxide fillet epoxy composites

In this study, the effect of mesoporous silicon dioxide (M-SiO2) additives with different surface areas and pore diameters on the morphological and mechanical properties of epoxy composites was investigated. For this purpose, M-SiO2 particles with different pore diameters and surface areas were synthesized from polyethylene glycol (PEG) with three different molecular weights (PEG2000 (PEG2), PEG6000 (PEG6), and PEG35000 (PEG35) kDa) using the one-step sol-gel technique. The mixing of epoxy resin, hardener and M-SiO2 fillers, was carried out in a mould followed by using ultrasonic bath and mechanical stirrer.The mechanical properties of the composites, including hardness, tensile strength, elongation at break, and modulus of elasticity, were studied. FT-IR spectra and XRD patterns show that M-SiO2 is distributed homogeneously in the epoxy. The epoxy/PEG35M-SiO2 composites' tensile strength (8.7%) and modulus of elasticity (23.3%) increased with the addition of PEG35M-SiO2, however their elongation at break (5.1%) decreased.

Preparation and characterization of hybrid PLA biocomposites reinforced by wood and silane treated basalt fibers or compatibilized by maleic anhydride‐grafted polypropylene (MAPP)

AbstractIn this study, basalt and/or beech wood fibers were treated with vinyltrimethoxysilane or compatibilized by maleic anhydride‐ grafted polypropylene (MAPP) to produce hybrid polylactic acid (PLA) biocomposites. Twin‐screw extruder was used to produce biocomposites, following by a hot press to form samples. Physical and mechanical properties of composites that were produced from both treated and untreated fibers were compared. Chemical, morphological, and thermal analysis of biocomposites were analyzed with TGA, FTIR and SEM, respectively. The results showed that silane treated basalt/wood fiber reinforced PLA (PBWS) and silane treated basalt reinforced PLA (PBS) have significantly better flexural strength than neat PLA. Besides, basalt reinforced bio‐composites except PBW3 and PBWM variations have significantly superior impact strength than neat PLA. Utilization of compatibilizers also reduced thickness swelling and water uptake features of biocomposites. All the above experimental data showed that the utilization of silane compatibilizer has better impact on properties than MAPP for such wood/basalt hybrid composite.Highlights Hybrid biocomposites with wood and basalt fibers by using coupling agents were prepared for the first time. Hybridization of organic and inorganic fibers gave promising results. Silane and maleic anhydride compatibilization improves physical properties. Vinyltrimethoxy silane grafted basalt fiber improves flexural strength significantly. Silanization of wood or basalt fibers enhances significantly the impact strength.

Impact of the Curing Temperature on the Manufacturing Process of Multi-Nanoparticle-Reinforced Epoxy Matrix Composites.

This study aims to analyze the effect of the curing temperature of nano-reinforcements during the manufacturing process on the mechanical properties of composites involving graphene (GNP), carbon nanofibers (CNFs), and a hybrid mixture of these two nanoparticles. In this context, the type of nanoparticles, their content, their type of resin, and their hybridization were considered. The results showed that both nanoparticles increased the viscosity of the resin suspension, with an increase of between 16.3% and 38.2% for GNP nanoparticles and 45.4% and 74% for CNFs depending on the type of resin. Shrinkage was also affected by the addition of nanoparticles, as the highest results were obtained with GNP nanoparticles, with a 91% increase compared with the neat resin, and the lowest results were obtained with CNFs, with a decrease of 77% compared with the neat resin. A curing temperature of 5 °C promoted the best bending and hardness performance for all composites regardless of the type of resin and reinforcement used, with improvements of up to 24.8% for GNP nanoparticles and 13.52% for CNFs compared with the neat resin at 20 °C. Hybridization led to further improvements in bending properties and hardness compared with single-reinforcement composites due to a synergistic effect. However, the effectiveness of hybridization depends on the type of resin.

Developing Eco-Friendly 3D-Printing Composite Filament: Utilizing Palm Midrib to Reinforce High-Density Polyethylene Matrix in Design Applications.

Designers actively pursue the use of novel materials and concepts in furniture and interior design. By providing insights into their processing behavior and suitability for 3D-printing processes, this research helps to highlight the potential of using waste materials to create more environmentally friendly and sustainable 3D-printing filaments that can be used in furniture and interior design. Furthermore, the study evaluates the effect of incorporating palm midrib nanoparticles (DPFNPs) to reinforce a high-density polyethylene (HDPE) matrix with different loadings such as 10, 20, 30, 40, and 50 wt.%. The composites were extruded into filaments using a manual extruder, which was then utilized to fabricate 3D-printed specimens using a 3D-printing pen. The effect of adding DPFNPs on the composite's chemical, thermal, and mechanical properties was evaluated, with a particular focus on how these modifications influence the melt flow rate (MFR) and, subsequently, the material's printability. The results revealed that HDPE and filament composites presented similar FTIR spectra. On the other hand, the filament composites presented an increase in the thermal stability and a decrease in the mechanical strength with increasing DPFNP content in the HDPE matrix. The filaments were successfully printed using a 3D-printing pen. Thus, using DPFNPs in the HDPE matrix presents a low-cost alternative for filament production and may expand 3D-printing applications in interior and furniture design with more sustainable materials. Future work will delve into optimizing these composites for improved printability and assessing their recyclability, aiming to broaden their applications in 3D printing and beyond.

Effect of fiber orientation on mechanical properties of betel nut (areca palm) stem fiber reinforced laminated polyester composites

ABSTRACT This study explored the effect of fibre orientation on the mechanical properties of Betel Nut (Areca palm) stem fibres (BNSF)-reinforced laminated polyester composites. Composites are fabricated by hand lay-up method with 15% (vol.) fibre loading and 0°/90°/0° and −45°/0°/45° orientations. The mechanical properties of composites are determined by testing as per ASTM standards and revealed that composite strengths vary significantly with fibre orientation. The tensile, flexural, and impact strengths of the composite are found 58.19 MPa, 153.96 MPa, and 25.68 kJ/m2, respectively, for the 0°/90°/0° fibre orientation, which are higher than the composite of −45°/0°/45° fibre orientation. Furthermore, strengths are found greater than the betel nut husk and leaf, bamboo, coir, banana, and jute fibres-reinforced polymer composites. The bonding between fibres and matrix, voids, micro-cracks, etc. are investigated by optical microscopy of a tensile-fractured specimen. This study revealed that BNSF would be a novel and potential natural fibre for reinforcing polymer composites. Its strength can be enhanced by choosing suitable numbers of fibre laminations and orientations. Since areca palm trees grow extended, moderate-sized composite boards/panels can be produced from BNSF to replace synthetic fibres-based ones. It will help reduce environmental pollution as a green composite.

The Synergistic Effect of Carbon Black/Carbon Nanotube Hybrid Fillers on the Physical and Mechanical Properties of EPDM Composites after Exposure to High-Pressure Hydrogen Gas.

This study investigated the synergistic effect of carbon black/multi-wall carbon nanotube (CB/MWCNT) hybrid fillers on the physical and mechanical properties of Ethylene propylene diene rubber (EPDM) composites after exposure to high-pressure hydrogen gas. The EPDM/CB/CNT hybrid composites were prepared by using the EPDM/MWCNT master batch (MB) with 10 phr CNTs to enhance the dispersion of CNTs in hybrid composites. The investigation included a detailed analysis of cure characteristics, crosslink density, Payne effect, mechanical properties, and hydrogen permeation properties. After exposure to 96.3 MPa hydrogen gas, the hydrogen uptake and the change in volume and mechanical properties of the composites were assessed. We found that as the MWCNT volume fraction in fillers increased, the crosslink density, filler-filler interaction, and modulus of hybrid composites increased. The hydrogen uptake and the solubility of the composites decreased with an increasing MWCNT volume fraction in fillers. Moreover, after exposure to hydrogen gas, the change in volume and mechanical properties exhibited a diminishing trend with a higher MWCNT volume fraction. We conclude that the hybridization of CB and CNTs formed strong filler-filler networks in hybrid composites, consequently reinforcing the EPDM composites and enhancing the barrier properties of hydrogen gas.

Performance of Flax/Epoxy Composites Made from Fabrics of Different Structures

Flax fibers have been shown to have comparable mechanical properties to some conventional synthetic fibers. Flax fabrics with different textile structures show differences in resistance against mechanical loads mainly rooted in fabric orientation and the resultant resin impregnation. Thus, in this study, flax fabrics with three different textile structures, fine twill weave, coarse twill weave and unidirectional, were used as reinforcements in an epoxy matrix. The surfaces of the fabrics were chemically treated using an alkaline treatment, and the alterations in fabric crystallinity index (CrI) were determined using X-ray diffraction (XRD). Experimental results confirmed that textile structures and CrI had significant effects on the mechanical properties of composites. Although an increment in CrI, resulting from chemical treatment, always enhanced tensile and flexural properties, it adversely affected damage development once composites were exposed to impact load. In terms of textile structures, unidirectional fabric outperformed woven fabrics in tensile and flexural properties while in impact properties, the latter had a better performance inducing less damage development. Finally, the mechanism of damage development in different composites was discussed in detail using Scanning Electron Microscopy (SEM) images. It is envisaged that the results of this study will provide an insight that will lead to the proper choice of the optimal kind of flax fabric for different applications.

Oxygen permeation mass transfer modeling and onion-like micromechanical modeling to predict the effect of multilayered interface on oxidation resistance and mechanical properties of composites

To predict oxidative damage of interfaces and fibers under high temperature aerobic environment and mechanical strength of composites before and after oxidation, oxygen permeation mass transfer modeling and onion-like micromechanical modeling of multilayered interface were proposed. The oxygen mass transfer theory and oxidation damage theory of PyC interface were used to establish the two models. The oxidative damage of PyC interface was extended to (PyC-SiC)n multilayered interface, and transformation of SiC phase and microcracks caused by thermal mismatch were also considered. The law of oxygen permeation mass transfer and the evolution of fiber oxidative damage in the “Carbon fiber/(PyC-SiC)n multilayered interface” region were revealed. The mechanical strength of composites under different interface layers was researched, resembling an onion-like wrapping in layers from the core outwards. Furthermore, Cf@(PyC-SiC)n/SiC(n = 1/2/3/4) composites were prepared by chemical vapor infiltration (CVI) method. The mechanical properties of the composites were tested before and after oxidation. A comparison was made between the experimental and predicted tensile strengths before and after oxidation. The predicted results of tensile strength were found to be in good agreement with the experimental ones. In addition, the results show that PyC-SiC multilayered interface has a positive effect on the tensile strength of the composites, mainly as the cracks are deflected and branched by the multilayered interface to promote the multistage pull-out of the fibers. With the increase of interface number, the oxygen diffusion path was lengthened and zigzagged, reducing the oxidative damage of fiber and interface.

False banana fiber reinforced geopolymer composite – A novel sustainable material

A new geopolymer composite material was produced using low-calcium fly ash and false banana plant fiber. The effect of fiber content and length on the mechanical and microstructural properties of the resulting composite material was investigated. Results showed that the addition of alkali-treated false banana fiber significantly improved the compressive and splitting tensile strength of the composites. In particular, incorporating a 10 mm length fiber at a 1.4 % volume fraction increased compressive and splitting tensile strength by 31 % and 33 %, respectively, when compared to the pure geopolymer paste specimens. Furthermore, unlike the neat geopolymer paste specimens, all composites failed gracefully. In addition to this, FTIR absorption peaks and SEM micrographs demonstrated that alkali treatment effectively changes fiber morphology and chemical characteristics. Additionally, fiber pull-out, fiber bridging, and fiber fracture were identified as energy-absorbing mechanisms responsible for increasing the mechanical properties of the composites. In general, the results showed that using natural false banana fiber as reinforcement enhances the mechanical properties of geopolymer composites, making them a more environmentally friendly alternative to synthetic fibers in composite production.