Fibers and Polymers最新文献

This study systematically investigates the effects of hot roller compaction process parameters (temperature, pressure, speed) on the mechanical properties and microstructure of 3D-printed continuous fiber-reinforced composites (continuous FRPs). Through comparative and orthogonal experiments combined with SEM characterization, two quantitative models were established to elucidate the underlying mechanisms: (1) a Weibull porosity–tensile strength probabilistic model demonstrating that reduced porosity (from 6.2 to 1.1%) contributes to a 11.5% strength enhancement, and (2) a modified Halpin–Tsai fiber orientation-equivalent modulus model showing improved fiber alignment (from 18.3° to 5.2° standard deviation) increases modulus by 23%. The synergistic optimization of these mechanisms through roller compaction (1 kg, 190 °C, 7 mm/s) achieved a 37% strength improvement (2410.2 N) beyond fiber reinforcement alone, while simultaneously reducing porosity and enhancing fiber orientation. These models provide fundamental insights into the microstructure–property relationships and establish an optimized parameter window for high-performance continuous FRP additive manufacturing. The findings offer both theoretical guidance and practical solutions for improving the mechanical performance of 3D-printed continuous fiber-reinforced composites.

Molecular dynamics simulations were conducted to investigate the thermomechanical behavior of epoxy networks based on triglycidyl p–aminophenol (TGAP) cured with two positional isomers of diaminodiphenyl sulfone (DDS), 3,3′–DDS and 4,4′–DDS. Thermal analysis revealed that the 4,4′–DDS system exhibited a higher glass transition temperature (533.35 K) and lower coefficient of linear thermal expansion (49.4 × 10⁻⁶ K⁻¹), while the 3,3′–DDS system showed a lower T_g (506.55 K) and higher CLTE (52.7 × 10⁻⁶ K⁻¹). Conversely, the 3,3′–DDS system exhibited a higher Young’s modulus of 4.05 GPa, compared to 3.87 GPa for the 4,4′–DDS system. To better understand these differences, analyses of fractional free volume, cohesive energy density (CED), and two types of molecular motions were performed, with molecular mobility measured via mean square displacement (MSD) reflecting overall translational dynamics, and segmental dynamics such as ring rotations capturing localized flexibility. The 3,3′–DDS displayed a lower fractional free volume and higher CED, indicating a more tightly packed network contributing to its greater mechanical stiffness. In contrast, the para–substituted geometry of the 4,4′–DDS system enabled localized molecular motions, which may enhance thermal adaptability and contribute to its higher thermal performance. These findings suggest that even subtle geometric differences in curing agents can influence molecular dynamics and the macroscopic performance of epoxy networks, providing useful insight for the design of materials tailored to specific engineering requirements.

With the advancement of society and technology, people are increasingly exposed to invisible sources of radiation in daily study, work, and life—such as mobile phones, televisions, computers, medical imaging equipment, and industrial radiographic instruments. There is now an urgent demand for environmentally friendly, lightweight, and flexible X-ray shielding materials. In this study, polypropylene (PP)–Bi₂O₃ and PP–WO₃ composite fibers were prepared by melt spinning, and, innovatively, Bi₂O₃, Gd₂O₃, and WO₃—three high-atomic-number fillers—were synergistically incorporated into the PP matrix in a single melt-spinning step to produce flexible fabrics. The materials were systematically characterized by X-ray shielding tests, scanning electron microscopy (SEM), single-fiber tensile testing, Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and fabric breathability test. The results demonstrate that these fabrics achieve good X-ray shielding performance in the 15–40 keV energy range. The materials combine low weight, high strength, and good thermal stability, can be produced at scale without complex post-processing, and show significant potential for application and market translation in medical diagnostic protection.

In this study, the prepared organically modified montmorillonite/polyvinyl alcohol composite material was applied to polyester fabrics via a padding–baking process to endow them with a certain water-repellent ability. The finished polyester fabrics were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, followed by performance testing including water contact angle, hydrostatic pressure, wash resistance, breaking strength, and air permeability, and the water-repellent effects of polyester fabrics treated with different amounts of organo-montmorillonite were also compared. The results showed that the water contact angle of the finished polyester fabric could reach up to 123.698°, and the hydrostatic pressure was 152.66 mmH₂O. After five washing cycles, the water contact angle of the fabric decreased by only about 10%, indicating that the polyester fabric achieved good water-repellent effect, which was attributed to the synergistic effect of organo-montmorillonite and polyvinyl alcohol. Furthermore, the breaking strength of the fabric was significantly improved, with the improvement range ranging from 10% to 35%. This study confirmed that montmorillonite, a natural mineral, can be used as a nanomaterial to construct a nano-rough structure on the fabric surface to achieve water-repellent effect, suggesting that montmorillonite has great potential as a fabric finishing agent.

The development of piezoelectric nanogenerators (PENGs) with enhanced performance, stability, and durability is crucial for the development of portable and autonomous electronic devices. In this study, flexible nanocomposite films were fabricated via electrospinning, combining a polyvinylidene fluoride–co-hexafluoropropylene (PVDF–HFP) polymer matrix with copper-doped barium titanate (CBT) nanoparticles at loadings ranging from 1 wt% to 16 wt%. The incorporation of CBT nanoparticles significantly increased the β-phase content and improved the dielectric properties of the film. The piezoelectric response was evaluated by finger tapping, and the pristine PVDF–HFP film generated an open-circuit voltage of 1 V and a current of 0.22 µA. With increasing CBT content, the dielectric constant increased from 12 to 67 at room temperature, and the maximum output voltage and current reached 2.56 V and 0.63 µA for the 16 wt% CBT nanocomposites. These findings demonstrate that PVDF–HFP/CBT nanocomposites exhibit superior piezoelectric performance compared to pure PVDF–HFP, highlighting their potential for lead-free energy harvesting and self-powered Internet-of-Things (IoT) applications.

An environmentally sustainable composite with good structural characteristics must be an alternative to the synthetic composite. Composite structures that are supportive to active/semi-active vibration control systems get usage in various aerospace, military, and automotive applications. This work attempts to develop an environmentally friendly composite and investigate its fundamental feasibility to consider as a semi-active vibration control system. In this work, the experimental and numerical investigations on the natural frequencies of a sandwich beam made of Woven Jute/Epoxy (WJE) skin and a Magneto-Rheological Elastomer (MRE) core are carried out at different magnetic fields under various boundary conditions. The experimentally determined natural frequencies are used to validate the natural frequencies obtained through the developed Finite Element (FE) model. Further, the validated FE model is used to investigate the variations of natural frequencies of the sandwich beam by considering various parameters such as the concentration of Carbonyl Iron Particle (CIP), magnetic field intensity, number of plies, ply orientation, and ply stacking sequence of skin and core-skin thickness ratios under the various boundary conditions. The study reveals that the presence of 50% CIP concentrated MRE sandwich beam exhibits higher natural frequencies than those of others. The increase in MRE core thickness results in better damping in spite of the increase in natural frequencies at fundamental modes. In addition, it is concluded that the magnetic permeability of WJE laminated composites does not play a significant role like the synthetic fiber composites. Even the skin’s ply sequence, ply orientation, and the volume fraction of fiber influence the natural frequencies through variation in its structural stiffness, but the fiber’s magnetic permeability does not contribute to it. This work makes the natural fiber-reinforced polymer composite structures an alternative to synthetic composite structures and allows them to evolve into an active or semi-active control system in the future.

Using electrospinning, bio-based polyamide 56 (PA56) and polyamide 510 (PA510) were fabricated into nanofiber membranes for use as positive electrode materials in triboelectric nanogenerators (TENGs). The results showed that under a mass fraction of 6%, a voltage of 10 kV, a flow rate of 0.8 mL/h, and a collecting distance of 15 cm, the PA56 nanofiber membrane exhibited uniform morphology with an average fiber diameter of 326.9 ± 6.6 nm. Similarly, under the same mass fraction, voltage, and collecting distance but with a flow rate of 1.0 mL/h, the PA510 membrane also showed good morphology, with an average fiber diameter of 546.5 ± 10.5 nm. At 4 Hz, the PA56-based TENG generated a maximum open-circuit voltage of 17.1 V and a short-circuit current of 2.1 μA, while the PA510-based TENG produced 25.2 V and 2.4 μA. In wearable applications, the PA510-based TENG produced open-circuit voltages of 3.5 V, 2.1 V, 4.9 V, and 3.4 V during simulated arm swinging, elbow bending, hand clapping, and walking motions, respectively, and successfully powered patterned LED displays. After 100 mechanical cycles, the output voltage of PA56- and PA510-based TENGs decreased by 7.5% and 9.1%, respectively, due to fiber surface damage. Both TENGs maintained stable open-circuit voltages over 120 days of sealed storage at room temperature.

Colored textiles with antibacterial properties are highly sought in the healthcare sector for surgical gowns and baby aprons. The study developed a novel, environmentally friendly process for producing dyed cellulose fabric with antibacterial properties. We investigated the use of Aloe vera leaf extract as an ecologically friendly reductant for vat-dyeing and the in situ synthesis and application of silver nanoparticles (SNPs) on cellulose fabric. The vat-dyed/SNP-finished cellulose fabric exhibited good color fastness, antibacterial, and UV protection performance, along with acceptable tensile strength, elongation, wettability, air permeability, crease recovery angle, and thermal stability. The SNPs expressed a narrow z-average size distribution. Surface chemical analysis expressed the successful application of nano-silver and vat dye on the cellulose fabric. DSC analysis revealed that the crystallization temperature of the cellulose fabric increased after nano-silver treatment. The enhanced crystallinity of the vat-dyed/SNP-treated cellulose fabric is also evident in its diffraction pattern, which exhibits crystalline peaks at 2θ angles of 17.6°, 22.3°, 26.0°, 35.3°, and 53.0°. The untreated cellulose showed a tensile strength of 250 N, while the vat-dyed/SNP-treated cellulose fabric had a tensile strength of 231 N. The treated cellulose fabrics expressed good antibacterial and UV protection properties. The vat-dyed/SNP-treated cellulose fabric expressed notable stability at pH 7. Overall, the A. vera leaf extract was qualified as the bio-based reductant for the co-reductive silver nano-finishing and vat-dyeing of cellulose fabric, making the process viable and sustainable.

The current work examines the buckling, damping, and vibration characteristics of hybrid sandwich plates reinforced with graphene. The sandwich plate is composed of graphene/epoxy/carbon fiber-reinforced composite skins and graphene/alumina fillers/epoxy reinforced composite core. The graphene/alumina filler-reinforced hybrid composite cores were fabricated using the sonication technique. Experiments were conducted to investigate the hybrid composite cores' microstructure and mechanical properties. The finite element formulation was built based on higher-order theory. The structural characteristics of the sandwich plates derived by the present formulation are compared with those of other authors and show excellent agreement. This paper also examines the impact of graphene, thickness ratio, and end conditions on the damping, buckling, and vibration characteristics of hybrid composites.

The rapid advancement of information technology has led to an increase in electromagnetic interference (EMI) issues, as electronic devices are now widely utilized, requiring materials with greater versatility. This study developed an efficient preparation method utilizing alternating vacuum filtration (AVF) technology to overcome this issue. Through the precise control of the deposition sequence of cellulose nanofibers (CNF)/Na-bentonite (NB) and MXene conductive layers, this study successfully prepared CNF/NB–MXene composite films with a well-structured alternating layered structure. The composite film exhibited a distinctive "brick–mortar" architecture, imparting favorable mechanical properties (i.e., 8.17 MPa tensile strength). Measuring 41 μm thick, the composite film exhibited a conductivity of 189.6 S m^–1, along with EMI shielding effectiveness (SE) of 34.3 dB and SE per unit thickness (SE/t) of 8365.85 dB cm^–1 in the X-band. Furthermore, the composite film demonstrated a high limiting oxygen index (LOI) of 36.5% and a residual carbon content exceeding 70%, which indicated exceptional flame retardancy. Consequently, the alternating layered composite film exhibited superior EMI performance and flame-retardant performance, making it particularly advantageous in harsh environments such as high temperatures.