pISSN : 1229-9197 / eISSN : 1875-0052
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Meta-materials of Re-entrant Negative Poisson’s Ratio Structures Made from Fiber-Reinforced Plastics: A Short Review
Changfang Zhao Jianlin Zhong Changfang Zhao Yangzuo Liu Jie Ren Chunhao Yang Zhendong Zhang
Negative Poisson’s ratio (NPR) structure is a common mechanical meta-material that has great potential in impact protection engineering due to its special indentation resistance. There are many studies on the NPR structures, but there are still few reports on the NPR structures with the parent materials of fiber-reinforced plastics (FRPs). As a type of advanced functional composites, the FRPs have higher specific modulus and specific energy absorption, and have become the most popular lightweight materials. In this review, the characteristics of NPR structures and FRPs were first analyzed and then the existing structure shapes, material types, manufacturing processes and mechanical behaviors were reported and discussed. Finally, the future direction of the mechanical meta-materials with the NPR structure was explored based on the current engineering requirements and preparation technologies. This review is expected to attract more scholars to pay more attention to the NPR structures fabricated by the FRPs.
Carlos Delgado Carlos A. Delgado Adriana Chapa Karen Lozano Arturo Fuentes Horacio Vasquez
A novel process of in-situ production of particle decorated electrospun fibers was developed by generating, charging, and depositing micro–nano-particles onto fibers during the electro-spinning (ES) process. The generation and charge of micro–nano-graphite particles occurred in an ES setup due to the pulverization of a negatively charged carbon brush near the fiber collector. The setup includes an aluminum cylinder rotating at a constant speed and being used to collect the fibers during electrospinning. The cylinder is negatively charged to attract the fibers from a positively charged needle, both charged with high voltages. A carbon brush contacts the cylinder to apply and maintain it connected to the negative voltage while it is rotating. Due to specific orientation and surface roughness, the carbon brush suffered wear which produced a graphite dust cloud around the collector. Nanofiber mats were produced with a unique characteristic appearance, creating as a result graphite coated fiber mat. These fiber mats were analyzed using scanning electron microscopy characterization and imaging. Results led to the discovery of coarse graphite particles embedded uniformly and in great quantities along the produced fibers. Therefore, fiber mats covered with graphite particles in a single-step electrospinning process were created and the method could be expanded to other material systems. This newly discovered in-situ deposition method could be beneficial to future studies about the effects of particle additives on the morphology and properties of the fiber mats for different
Advanced Piezoelectric Composite Fibers with Shape Memory Polyurethane for Energy-Harvesting Applications
Xiaoyu Guan Yuefen Han Chunyan Lou Anqi Li Xinqi Wang Heng Zhang Xiaoyu Guan
To overcome the drawbacks of previous piezoelectric composite fibers and fabrics with excessive stiffness, this paper explores the fabrication of flexible piezoelectric composite fibers using shape memory polyurethane (SMPU) and lead zirconate titanate (PZT) piezoelectric material through a melt-spinning technique. While the shape recovery performance of the PZT/SMPU composite fibers with 60% PZT content experiences a slight reduction, it still achieves a level of 64.56%. Furthermore, the composite piezoelectric fabric with 60% PZT content generates an output voltage of 70.72 mV under sinusoidal vibration conditions at 10 μm. The polymer matrix significantly enhances the flexibility of the composite material, effectively encapsulating the PZT piezoelectric material and transferring external stress to it, thereby converting mechanical energy into electrical energy. Moreover, due to the characteristics of the shape memory effect, fabrics woven from PZT/SMPU composite fibers can easily deform into various shapes. Consequently, flexible piezoelectric composite fabrics offer superior comfort to the human body while being capable of bending into multiple forms, enabling the conversion of vibrational energy into electrical energy. This underscores the promising applications of flexible composite fabrics in the field of energy harvesting.
Kui Zhou Kui Zhou Hongwei Chen Zhenyu Xu Jiaqi Zeng Ming Cao
By soaking polycaprolactone (PCL) scaffolds in a PCL solution, the surface properties of the scaffolds can be modified to improve early bone formation. In the presented study, scaffolds composed of PCL and hydroxyapatite nanowires (HAW) were fabricated by cryogenic extrusion printing. The scaffold surface was subsequently modified by self-induced crystallisation. In this study, the synthesized HAW and scaffolds were analyzed through X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). Additionally, the synthesized HAW was characterized using transmission electron microscopy (TEM). The findings indicate that the surface of PCL-HAW scaffolds developed lamellar crystals, resulting in surface roughness. Furthermore, the results of the biological experiments show that PCL-HAW scaffolds with a layered crystal structure on their surface have the potential to stimulate both proliferation and differentiation of osteogenic precursor cells (MC3T3-E1).
Binjie Xin Peijun Huang Yan Liu Zhuoming Chen Yuansheng Zheng Khammatova Venera Vasilovna Gainutdinov Ruslan Faritovich Binjie Xin
Polypyrrole (PPy) is one of the most widely researched conductive polymers due to its high electrical conductivity, good thermal and environmental stability, oxygen resistance, heterocyclic structure, non-toxicity, and simple synthesis method, and is an excellent candidate for electric heating materials. For better application in textile heating, a polyurethane (PU) film is used as a substrate and dopamine (PDA) is used as a multifunctional platform for the secondary reaction on the film to immobilize the polypyrrole on the surface of the film, making it a smart wearable element. By varying the amount of PPy to control its direct oxidative polymerization reaction, materials with good electrical conductivity and flexibility were obtained. It has a fast electrothermal response at low operating voltages (up to 118 °C after 20 s at 5 V), good flexibility, light weight and uniform heat distribution. It has significant advantages compared to other electrical heating materials.
Effective Impregnation of ε-Caprolactam with Polyamide 6 Oligomer in Thermoplastic Resin Transfer Molding
Han Chae Kyung Hyun Song Seung Mo Son Jae Hyo Lee Jung Jae Yoo Sang Woo Kim Jin Woo Yi Han Gi Chae Dong Gi Seong
The low-viscosity ε-caprolactam resin exhibits rapid infiltration in thermoplastic resin transfer molding (T-RTM), causing an unstable flow front at a macroscopic level and uneven impregnation between inter-/intra-tows. Uneven impregnation arises when there is a substantial difference between external and capillary pressures, resulting in the formation of micro-/macrovoids in the fiber preform. To address this issue, we propose to minimize total void content by regulating key parameters (contact angle between resin and carbon fiber, surface tension, viscosity, and resin infiltration viscosity) related to capillary pressure. Unlike previous studies focused on optimizing impregnation velocity through external pressure control, our approach employs polyamide 6 oligomers to enhance the compatibility between ε-caprolactam resin and carbon fiber, reducing the contact angle and minimizing void content by managing capillary pressure.
Optimizing Acoustic Performance: Electrospun Polycaprolactone Fiber Mat Associated with Melamine Foam and Fiber Glass Wool
Marcelo Minetto Garcia Duarte Marcelo Minetto Garcia Duarte Rita Aparecida Zoppi Alberto Luiz Serpa
Excessive exposure to noises, which corresponds to unwanted and/or unpleasant sounds, poses as a threat to people’s health and can cause irritability, insomnia and even hearing loss. To attenuate noises, sound absorbers usually composed of porous materials are widely used. These, which appear as large networks of interconnected pores, are capable of absorbing medium and high sound frequencies, specially, transforming into heat the majority of the sound energy that reaches them. Such dissipations occur due to viscous, thermal and inertial losses resulted from interactions between the solid and fluid phases from which the porous materials are composed of. With the growing demand for acoustic comfort, one of the most important topics in noise control engineering is currently the search for sound absorption materials that provide attenuations in wide frequency ranges with minimum cost, weight and thickness. Fiberglass wool and melamine foam are widely used, and a variety of new porous materials are being developed, such as polymer micro- and nanofiber mats obtained by electrospinning. It is here investigated the acoustic potential of the electrospun polycaprolactone (PCL) fiber mat, normally used as a biomaterial. The sound absorption capacity of a material is given by its sound absorption coefficient (α), while its sound insulation capacity is denoted by its transmission loss (TL), and these are normally conflicting. In an impedance tube, through the transfer function and the transfer matrix methods, α and TL curves are here determined for samples of fiberglass wool and melamine foam with 25 mm width, and later these combined with a layer of approximately 0.3 mm of PCL fiber mat. With the addition of a fine layer of those polymeric fibers to both base materials, it was observed expressive gains in the sound absorption and transmission loss potentials in almost all the totality of the frequency range analyzed, which extends from 400 to 2500 Hz. It was also analyzed the morphology of the study materials through Scanning Electron Microscopy (SEM), and their porosities were determined through an optical approach with the aid of X-ray microtomography.
Development of Biodegradable Poly(butylene succinate) Based Nanofibrous Webs via Solution-Blow Spinning Technology for N95 Respiratory Filters
Ayben Pakolpakçil Ayben Pakolpakçil
As a result of the COVID-19 outbreak, millions of people are wearing face masks (including disposable surgical face masks), and many used masks, particularly disposable masks, are entering the environment and increasing pollution. The applicability of nanofibers in the field of filtration is considerable, and it has replaced environmentally friendly materials in research in this area. Solution-blown spinning (SBS) is an efficient and straightforward method for creating micro and nanofibers that allow quick fiber deposition on any substrate. Poly(butylene succinate) (PBS) is an environmentally safe biopolymer with unique properties, such as processability and flexibility, that has piqued the interest of industry and researchers. Hence, an eco-friendly air filter based on PBS nanofibers was fabricated using SBS. This solution-blown spun PBS filter was demonstrated as an air filter for the first time. The findings demonstrated that a weight of around 19.3 g/m2 PBS webs with a mean diameter of 199 nm was adequate to produce a filtering performance of 95.26% with a pressure drop of 251 Pa at a flow rate of 85 L/min. The fast and economic features of the SBS process, as well as the environmentally friendly nature of the PBS polymer, may be a considerable contribution to the development of green filters.
In Vitro Properties of Electrospun Composite Fibers Containing Boric Acid and Enhanced with Epidermal Growth Factor for Wound Dressing Applications
Bengi Yilmaz Habip Orhan Bengi Yilmaz
The requirements of the wound microenvironment, involving pH regulation, mechanical compatibility with skin, and prevention of bacterial attachment, highlight crucial considerations for advanced wound dressings. This study focused on electrospinning of poly(L-lactide-co-ε-caprolactone) (PLCL) enriched with 3–5% boric acid particles. The fibers were also supplemented with epidermal growth factor (EGF) prior to in vitro cell culture experiments. The results revealed that the fibers, with micro-to-nano thickness, displayed unique morphologies as boric acid particles interacted with the PLCL. Boric acid-containing fibers showed lower swelling rates compared to pure PLCL fibers that achieved a swelling rate of 151 ± 10.3%. Nevertheless, they maintained slightly acidic conditions and adequate oxygen conductivity in vitro. The water vapor transmission rate (WVTR) of fibers produced using a 5% boric acid-added PLCL was measured at 557 ± 20.9 g/m2day at 24 h, demonstrating competitive performance with commercial products. The incorporation of 5% boric acid in PLCL fibers significantly improved their maximum tensile stress, reaching 11.31 ± 0.82 MPa, as opposed to pure PLCL, which attained 6.92 ± 2.08 MPa. The Young's modulus values were determined as 190.53 ± 64.80 MPa for pure PLCL and 224.74 ± 91.66 MPa for PLCL containing 5% boric acid. In vitro fibroblast cell (3T3) proliferation on all fiber types did not show a significant difference compared to control. Fluorescent microscopy displayed a good adhesion and spread of cells on boric acid containing fibers. The addition of boric acid drastically reduced the attachment of Escherichia coli. The findings demonstrated the promising potential of electrospun PLCL fibers with incorporated boric acid as wound dressings.
Xiaojun Chen Xiaojun Chen Deyun Mo Zaifu Cui Xin Li Haishan Lian
Micro/nano-devices with multi-level structure constructed via photo-curing 3D printing techniques had inherent defects including the sacrificial layer clogging caused by the micro/nano-scale maze effect of fluid and the liquid tension-induced capillary collapse. Moreover, movable film structures with poor elasticity were susceptible to cracking and deformation, resulting in fluid leakage and structural failure. Here, we proposed a new principle and method for micro/nano-devices with nanofiber self-consistent 3D printing. The mechanism of spreading and penetration between nanofibers and high viscosity fluids were investigated. Due to the behavior of viscosity, capillary force and surface tension, the high-viscosity fluid is suspended in the surface layer of the nanofiber membrane, expanded and permeated in the micro/nano-pores to form movable film structure. Nanofiber under the surface layer still maintains microporosity, which plays a role of supporting the surface movable film and local interconnection. Inspired from this, a nanofiber movable film-microcavity microfluidic device including hollow microfluidic structure and nanofiber self-consistent microfluidic structure were fabricated. A LED light was applied to verify the switching performance of the valve. This method exhibited a simple manufacturing process to design highly flexible structures, representing a great potential for promoting the mass production and integrated manufacturing of these devices.