Physical,Chemical and Mechanical Properties of Hibiscus sabdariffa Fiber/Polymer Composite

Tensile, compressive, flexural and wear resistance properties of Hibiscus sabdariffa fiber-reinforced phenolic (Resorcinol Formaldehyde) resin matrix-based composites were evaluated to assess the possibility of using these fibers as a new eco-friendly material in engineering applications. Polymer composite samples were fabricated by a compression-molding technique developed in our laboratory. The effect of fiber dimension on mechanical properties was evaluated. The interfacial bonding between Hibiscus sabdariffa fiber and the polymer matrix has been found to affect the mechanical properties of the resorcinol formaldehyde resin matrix. It has been observed that particle-reinforced polymer composites exhibit better mechanical properties as compared to short and long fiber-reinforced polymeric composites. These composites were further subjected to an evaluation of morphological, thermal, physical (swelling and moisture absorption) and chemical properties.     

Properties of Glass-Fiber Hybrid Composites: A Review

This paper provides a rigorous literature review in a field of glass-fiber composites. Glass-fiber composite is a type of fiber-reinforced polymer composites. Glass-fiber composite holds good properties such as low density, high strength, and easy processing, so widely used in aerospace, automotive, and construction. Fabrication of glass-fiber composite has been discussed in the present study. Combining the glass-fiber with other fibers into a single polymer matrix results in the development of hybrid glass-fiber composites. The hybridization in glass-fiber composites raised new ideas for future in the field of composites.     

A dynamic mechanical study on unidirectional carbon fiber-reinforced polypropylene composites

Fiber-reinforced polymer composites show high specific strength and stiffness. The alignment of reinforcing fibers results in anisotropy of the material. This anisotropic behavior has been studied through dynamic mechanical analysis of unidirectional carbon fiber-reinforced polypropylene (CFRPP) composites measured in both parallel and transverse directions to fiber arrangement. Several parameters such as storage modulus (E′), loss modulus (E″), loss factor or damping factor (tan δ), and complex viscosity (MU^*) have been determined over a wide range of frequencies and at a fixed temperature. Relaxation and retardation spectra have been constructed for these composites. Modulus enhancement occurs due to stiffness imparted by the fiber and efficient stress transfer at the interface. Relaxation of the polymer matrix ceases with increase in the volume fraction of the fibers. α′-relaxation is observed for the composite having a 13% volume fraction of fibers and is ascribed to relaxation in the crystalline phase where the additional crystallinity arises out of the transcrystalline growth at the fiber–matrix interface. There exists a good correlation between theroretical curves with the experimental ones. Relaxation and retardation spectra and the dynamic parameters determined for these composites show a good correlation with the volume fraction of fibers as well as the direction of the applied load. © 1994 John Wiley & Sons, Inc.     

Improvement in mechanical and thermal properties of unsaturated polyester- based hybrid composites

Polymer matrix composites are used in automobile, structure and aerospace industries due to their light weight and high strength. The present research has an aim to reinforce locally developed silica nanoparticles and glass fibers in unsaturated polyester to produce polymer-based hybrid composites. Composites were synthesized by hand lay-up method with 1, 2, 3 and 4 wt% of silica sand nanoparticles and glass fiber. Mechanical tests like tensile, impact and micro-hardness were performed on the obtained polymer hybrid composites. The results of mechanical properties of the hybrid polymer matrix composites revealed an increasing trend. The SEM analysis was performed on the developed and fractured tensile testing samples. The SEM analysis showed the presence of silica nanoparticles in the samples and pulling action of fibers were seen under fractured tensile tests. The pulling actions of fibers from polymer matrix delayed the fractured mechanism and enhanced the mechanical properties. Silica nanoparticles filled the cavities generated during tensile test and extensive enhancement was revealed in tensile as well as impact energy. Toughness of the hybrid composite was also enhanced as a result. The thermal properties of the hybrid polymer composites were analyzed using thermogravimetric analysis. Thermal stability of the composite has been marginally increased with increasing wt% of reinforcement.     

FRP层合板低速冲击损伤特性研究现状与展望

纤维增强复合材料层合板(FRP)由于具有比强度高、比模量高、可设计性强等特性,在工程领域得到越来越广泛的应用。但是低速冲击造成的损伤对层合板力学性能的影响非常显著,导致其强度和刚度下降。本文针对近年来纤维增强复合材料层合板低速冲击作用下的损伤研究进行了综述和回顾,重点介绍了试验研究方法、模拟计算研究方法、FRP层合板损伤性能表征方法,并对有待于进一步研究的问题进行了展望。     

Effect of chemical treatment on the thermal properties of hybrid natural fiber-reinforced composites

The main objective of this work is to study the effect of chemical treatment on the thermal properties of hybrid natural fiber-reinforced composites (NFRCs). Different chemical treatments [i.e., alkalized and mixed (alkalized+ silanized)] were used to improve the adhesion between the natural fibers (jute, ramie, sisal, and curauá) and the polymer matrix. A differential scanning calorimetry, thermogravimetry, and a dynamic mechanical analysis were performed to study the thermal properties of hybrid NFRC. It was found that the chemical treatments increased the thermal stability of the composites. Scanning electron microscopy images showed that the chemical treatments altered the morphology of the natural fibers. A rougher surface was observed in case of alkali treated fiber, whereas a thin coating layer was formed on the fiber surface during the mixed treatment. However, for some fibers (i.e., sisal and rami), the chemical treatment has a positive impact on the composite properties, whereas for the jute and curauá composites, the best behavior was found for untreated fibers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47154.     

Mechanical properties of short fiber reinforced thermoplastic blends

An immiscible thermoplastic component was added to a conventional short fiber reinforced polymer to study its effect on the mechanical properties of the composite. Because of the preferential wetting of the fiber reinforcement a continuous network was formed of fibers ‘welded’ together by the minor component within the matrix polymer.Polyethylene (PE) was used as the matrix, polyamide-6 (PA6) as dispersed polymer phase and glass fibers (GF) as reinforcement. The obtained composite retained unusually high values of the elasticity modulus at temperatures above the melting point of the matrix. The upper limit of the ‘applicability’ of the material is determined by the melting point of the minor component. A simple model was derived to describe the mechanical properties of the composite. The model shows a good agreement with the experimental data. The influence of the model parameters on the predictions of the model was examined.     

In situ composite fibers: Blends of liquid crystalline polymer and poly (ethylene terephthalate)

To augment the concept of in situ composites as alternatives to fiber-reinforced composites, polyblends of a thermotropic liquid crystalline polymer (LCP) and poly(ethylene terephthalate) (PET) were prepared. Fiber-spinning of the blends was performed on a piston-driven plastorneter. Blends of LCP and a low-intrinsic-viscosity PET resin showed poor mechanical performance, which was attributed to their processing behavior. Blends of LCP and a high intrinsicviscosity PET manifested an almost additive behavior with regard to tensile modulus and strength. Elongation of the blends, however, displayed a radical decline, which is reminiscent of fiber-reinforced composites. Heat treatment of the blend fibers modestly increased the tensile properties of the LCP-rich compositions. Blend fibers from PET-rich compositions exhibit a moderate decline in tensile properties owing to thermal relaxation of PET. The data demonstrate that in situ composites or blends of thermotropic LCPs and isotropic polymers present challenging alternatives to fiber-reinforced composite systems because of their ease of processing.     

电子束辐射接枝对PAN基碳纤维的表面改性

采用电子束加速器辐射接枝方法对聚丙烯腈(PAN)基碳纤维进行表面改性,研究了接枝单体种类对接枝率及其环氧树脂基复合材料力学性能的影响,分析了辐射接枝前后PAN基碳纤维的表面形貌与化学结构以及其复合材料界面断口的形貌变化。结果表明:电子束辐射接枝改性的PAN基碳纤维表面粗糙度增加,表面活性官能团增多,与树脂的机械锲合作用增强,其树脂基复合材料断口表而较为平整;乙二胺/水溶液体系是辐射接枝改性的理想溶液,在200 kGy的电子束辐射下,PAN基碳纤维表面的接枝率为6.66%,复合材料的层间剪切强度提高了45.1%。     

Surface modification of textile fibers for improvement of adhesion to polymeric matrices: a review

Surface treatments have long been utilized to modify the chemical and physical structures of the surface layers of textile fibers, thus improving the properties of fibers in many applications. This review discusses the feasibility and characteristics of different methods of surface modification of polymeric textile fibers, focusing on tailoring fiber-matrix bond strength in fiber-reinforced composite materials. The influence of various treatments on the chemical and mechanical properties of different fibers is discussed. Some very recent developments in surface modification of textile fibers are highlighted.     

Investigation on the effect of fiber wettability on water absorption kinetics of geopolymer composites

Fiber-reinforced geopolymer composites receive widespread attention due to their desirable mechanical properties but the effect of fiber wettability on the water transport properties is rarely investigated. This work aims to reveal the effect and mechanism of hydrophilic and hydrophobic fibers, represented by polyvinyl alcohol fiber (PVAF) and polypropylene fiber (PPF), on the water absorption kinetics of geopolymer composites. Results indicate that both fibers can slightly weaken the water absorption capacity due to increased micron-scale voids and capillary length. Moreover, waterproof composite with a water contact angle of ～120° can be fabricated by adding PPF and polydimethylsiloxane. PPF weakens the vaporization-condensation process of moisture, thereby extending the duration of the induction stage by 16.7 h, within which a low water absorption rate is maintained. In contrast, hydrophilic PVAF promotes the water absorption process. Therefore, hydrophobic fibers are more beneficial to improve the waterproof performance of geopolymer composites. The development of waterproof fiber-reinforced geopolymer composites is of great potential to improve the corrosion resistance and durability of buildings serving in high-humidity environments.     

Mechanical and shape‐memory behavior of shape‐memory polymer composites with hybrid fillers

Shape‐memory polymer (SMP) materials have several drawbacks such as low strength, low stiffness and natural insulating tendencies, which seriously limit their development and applications. Much effort has been made to improve their mechanical properties by adding particle or fiber fillers to reinforce the polymer matrix. However, this often leads to the mechanical properties being enhanced slightly, but the shape‐memory effect of reinforced SMP composites being drastically reduced. The experimental results reported here suggested that the mechanical resistive loading and thermal conductivity of a composite (with hybrid filler content of 7.0 wt%) were improved by 160 and 200%, respectively, in comparison with those of pure bulk SMP. Also, the glass transition temperature of the composite was enhanced to 57.28 °C from the 46.38 °C of a composite filled with 5.5 wt% hybrid filler, as determined from differential scanning calorimetry measurements. Finally, the temperature distribution and recovery behavior of specimens were recorded with infrared video in a recovery test, where a 28 V direct current circuit was applied. The effectiveness of carbon black and short carbon fibers being incorporated into a SMP with shape recovery activated by electricity has been demonstrated. These hybrid fillers were explored to improve the mechanical and conductive properties of bulk SMP. Copyright © 2010 Society of Chemical Industry     

Mechanical Behavior of Fiber-Reinforced Cement-Based Composites

The use of fibers in a cement-based matrix can fundamentally improve its mechanical properties. Such improvement may lead to a new class of cement-based materials. Further developments depend on an understanding of the interaction between different fibers and cement-based matrices. The current knowledge on the mechanical behavior of fiber-reinforced cement-based composites is summarized. Toughening mechanisms, interface properties, and tensile response of fiber-reinforced cement-based composites are presented. Various theoretical approaches used to describe the mechanical behavior of fiber-reinforced composites are reviewed.     

Polyethylene composite fibers. I. Composite fibers of high‐density polyethylene

Polymer matrix composites are generally studied in the form of bulk solids, and very few works have examined composite fibers. The research described here extended such bulk studies to fibers. The question is whether or not what has been reported for bulk polymers will be the same in fibers. In this article are reported studies of high‐density polyethylene (HDPE), whereas those of linear low‐density polyethylene are reported in part II of this article series. Two types of filler were used, that is, organically modified montmorillonite (OMMT), in which the nanosized filler particles had a high aspect ratio, and microsized calcium carbonate (CaCO₃), with an aspect ratio nearer to unity. Composite fibers of both as‐spun and highly drawn forms were prepared, and their structures, morphology, and mechanical properties were studied. It was found that the microsized particles gave HDPE composite fibers with mechanical properties that were the same as those of the neat polymer. In the case of clay composite fibers, the clay interfered with the yield process, and the usual yield point could not be observed. The particle shape did not affect the mechanical properties. The fibers showed different deformation morphologies at low draw ratios. The CaCO₃ composite fibers showed cavities, which were indicative of low interaction between the polymer and the filler. The OMMT composite fibers showed platelets aligned along the fibers and good polymer–filler interaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A comparative investigation of bio waste filler (wood apple‐coconut) reinforced polymer composites

During the last century natural fibers are used as reinforcement in polymer composite has been continuously growing in the composite industry. This polymer matrix composite has wide range of application in hostile environment where it is exposed to external attacks such as solid particle erosion. The mechanical properties of different polymer composites are also most important characteristics. An attempt has been made to compare the mechanical and tribological properties of the both biowaste wood apple and coconut shell particulate polymer matrix composite. The results show that maximum flexural strength is obtained 78.19 MPa for wood apple shell and 68.25 MPa for coconut shell at 15 wt% filler content. The wood apple particulate composite shows best erosion and mechanical properties than coconut particulate composite. POLYM. COMPOS., 35:180–185, 2014. © 2013 Society of Plastics Engineers     

Properties of Recycled Polycarbonate/Waste Silk and Cotton Fiber Polymer Composites

Polymer-based composite structures have advantages over many other materials. The most important advantage is the higher mechanical properties obtained from the composites when supported by fiber reinforcement. The mechanical and thermal properties of fiber-reinforced composite structures are affected by the amount of fibers in the structures, orientation of the fibers and fiber length. Silk and cotton fibers are used in many fields but especially in clothing and textiles. However, there is not enough research on their usage as reinforcement fibers in composite structures. Silk fibers as a textile material have better physical and mechanical properties than other animal fibers. The improvement of the mechanical and physical properties of the composite structures allows them to be used in many areas. From economical, technological and environmental points of view, the improvement of mechanical and physical properties of polymeric materials are receiving much attention in recent studies.

In this study, different application areas were chosen to evaluate the waste silk and waste cotton rather than classic textile applications. Waste silk and cotton and recycled polycarbonate polymer were mixed and as a result composite structures were obtained. Silk and cotton waste fiber dimensions were in between 1 mm, 2.5 mm and 5 mm. The recycled PC/silk and cotton wastes were mixed in the rates of 97%/3%. Mixtures were prepared by twin-screw extruder. Tensile strength, % elongation, yield strength, elasticity modulus, Izod impact strength, melt flow index (MFI), heat deflection temperature (HDT) and Vicat softening temperature properties were determined. To determine the materials' thermal transition and microstructure properties, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used.     

纤维增强聚合物发泡体的研究进展

纤维增强聚合物发泡体是一种新型的三相复合材料，纤维增强发泡体可以大大提高发泡体的弹性模量和压缩模量，提高材料的破坏强度，也显著地降低了材料的收缩率，因而可用于结构性材料。纤维增强发泡体中纤维特性，长径比，用量，与基体的粘合状态，泡孔的大小，形状，发泡密度等因素对发泡体系的性能均有影响，其中粘合是非常生要的。过长的纤维由于结构缠结对聚合物发泡体的增强并不理想。     

Alumina fiber-reinforced silica matrix composites with improved mechanical properties prepared by a novel DCC-HVCI method

A novel direct coagulation casting via controlled release of high valence counter ions (DCC-HVCI) method was applied to prepare the alumina fiber-reinforced silica matrix composites with improved mechanical properties. In this method, the silica suspension could be rapidly coagulated via controlled release of calcium ions from calcium iodate and pH shift by hydrolysis of glycerol diacetate (GDA) at an elevated temperature. The influence of tetramethylammonium hydroxide (TMAOH) dispersant amount, volume fraction and calcium iodate concentration on the rheological properties of suspensions was investigated. Additionally, the effect of alumina fiber contents on the mechanical properties of alumina fiber-reinforced silica matrix composites was studied systematically. It was found that the stable suspension of 50 vol% solid loading could be prepared by adding 2.5 wt% TMAOH at room temperature. The addition of 0–15 wt% alumina fibers had no obvious effect on the viscosity of the silica suspension. The controlled coagulation of the suspension could be achieved by adding 6.5 g L⁻¹ calcium iodate and 1.0 wt% GDA after treating at 70 °C for 30 min. Compressive strength of green bodies with homogeneous microstructure was in the range of 2.1–3.1 MPa. Due to the fiber pull-out and fracture behaviors, the mechanical properties of alumina fiber-reinforced composites improved remarkably. The flexural strength of the composite with 10 wt% alumina fibers sintered at 1350 °C was about 7 times of that without fibers. The results indicate that this approach could provide a promising route to prepare complex-shaped fiber-reinforced ceramic matrix composites with uniform microstructure and high mechanical properties.     

Plasma-functionalized graphene fiber reinforced sulphoaluminate cement-based grouting materials

Fiber-reinforced cement-based grouting materials have aroused intensive attention due to the promising applications in coal mining. However, how to enable a fiber-cement grouting material with high mechanical strength and stability, and meanwhile with favorable toughness and electrical conductivity, still remains challenging. Herein, a facile and effective strategy to solve the problem was proposed by developing a plasma-functionalized graphene fiber (PGF) with the combined feature of excellent flexibility, good dispersion, high surface roughness and tensile strength, via the wet spinning and oxygen plasma etching. Thanks to the uniform distribution and strong interfacial interaction of PGFs in the cement matrix, the resultant PGF-sulphoaluminate cement grouting materials with water-cement ratio of 0.8 and 0.3% PGF dosage delivered the compressive and flexural strengths of 18.6 and 3.7 MPa after curing for 7 days, respectively, 1.1 and 1.3 times higher than that of control samples, respectively. Meanwhile, resulted from the formation of a continuous and homogeneous conductive network consisting of PGFs in the cement matrix, the composite featured a significant improvement of electrical conductivity. This work has shed light on new strategies for fabricating fiber-reinforced cement-based grouting materials with high mechanical strength, toughness and electrical conductivity toward future uses.     

Investigation of Properties of Polymer/Textile Fiber Composites

Polymer-based composite structures have advantages over other materials. The most important advantage is the higher mechanical properties obtained from the composites when supported by fiber reinforcement. The mechanical and thermal properties of fiber-reinforced composite structures are affected by the amount of fibers in the structures, orientation of the fiber and fiber length. Silk and cotton fibers are used in many fields but especially in clothing and textiles. However, there is not enough research on their usage as reinforcement fibers in composite structures. Silk fibers as a textile material have better physical and mechanic properties than other animal fibers. It is very important that the improvement of the mechanical and physical properties of the composite structures allows them to be used in many areas. From economical, technological and environmental points of view, the improved the mechanical and physical properties of polymeric materials are receiving much attention in the recent studies.

In this study, various lengths (1 mm–2.5 mm and 5 mm) of waste silk and waste cotton fibers were added to high-density polyethylene (HDPE) and polypropylene (PP) polymer in the mixing ratios of (polymer:fiber) 100%:0%, 97%:3%, and 94%:6% to produce composite structures. On the other hand, known lengths (1–2.5–5 mm) of waste silk and waste cotton fibers were added to recycled polyamide-6 (PA₆) and polycarbonate (PC) polymers in mixing quantities of 100%-0%, 97%-3%. A twin-screw extruder was employed for the production of composites. Tensile strength, % elongation, yield strength, elasticity modulus, Izod impact strength, melt flow index (MFI), heat deflection temperature (HDT), and Vicat softening temperature properties were determined. In order to determine the materials' thermal transition and microstructure properties, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used. Results have shown that cotton and silk fibers behave differently than in the composite structure. Waste silk fiber composites give better mechanical properties than waste cotton fiber.