Influence of fiber content on the mechanical and dynamic mechanical properties of glass/ramie polymer composites

The combination of glass and ramie fibers with a polyester matrix can produce a hybrid material that is competitive to all glass composites (e.g. those used in the automobile industry). In this work, glass and ramie fibers cut to 45 mm in length were used to produce hybrid polymer composites by resin transfer molding (RTM), aiming to evaluate their physical, mechanical and dynamic mechanical properties as a function of the relative glass–ramie volume fractions and the overall fiber content (10, 21 and 31 vol.%). Higher fiber content and higher ramie fiber fraction in the hybrid composites yielded lower weight composites, but higher water absorption in the composite. The mechanical properties (impact and interlaminar shear strength) of the composites were improved by using higher fiber content, and the composite with 31 vol.% of reinforcement yielded the lowest value for the reinforcement effectiveness coefficient C, as expected. Although the mechanical properties were improved for higher fiber content, the glass transition temperature did not vary significantly. Additionally, as found by analyzing the adhesion factor A, improved adhesion tended to occur for the composites with lower fiber content (10%) and higher ramie fiber fraction (0:100) and the results for the adhesion factor A did not correspond to those found by the analysis of the tan delta peak height.     

Effect of Seawater and Warm Environment on Glass/Epoxy and Glass/Polyurethane Composites

A study of the durability of fiber reinforced polymer (FRP) materials in seawater and warm environment is presented in this paper. The major objective of the study is to evaluate the effects of seawater and temperature on the structural properties of glass/epoxy and glass/polyurethane composite materials. These effects were studied in terms of seawater absorption, permeation of salt and contaminants, chemical and physical bonds at the interface, degradation in mechanical properties, and failure mechanisms. Test parameters included immersion time, ranging from 3 months to 1 year, and temperature including room temperature and 65°C. Seawater absorption increased with immersion time and with temperature. The matrix in both composites was efficient in protecting the fibers from corrosive elements in seawater; however moisture creates a dual mechanism of stress relaxation—swelling—mechanical adhesion, and breakdown of chemical bonds between fiber and matrix at the interface. It is observed that high temperature accelerates the degradation mechanism in the glass/polyurethane composite. No significant changes were observed in tensile strength of glass/epoxy and in the modulus of both glass/epoxy and glass/polyurethane composites. However, the tensile strength of the glass/polyurethane composite decreased by 19% after 1 year of exposure to seawater at room temperature and by 31% after 1 year of exposure at 65°C. Plasticization due to moisture absorption leads to ductile failure in the matrix, but this can be reversed in glass/polyurethane composites after extended exposure to seawater at high temperature where brittle failure of matrix and fiber were observed.     

Properties enhancement using oil palm shell nanoparticles of fibers reinforced polyester hybrid composites

Oil palm shell (OPS) nanoparticles were utilized as filler in fibers reinforced polyester hybrid composites. The OPS nanoparticles were successfully produced from the raw OPS using high-energy ball milling process. Fundamental properties including morphology, crystalline size, and particle size of the OPS nanoparticles were determined. Tri-layer natural fiber reinforcement (kenaf–coconut–kenaf fiber mat) polyester hybrid composites were prepared by hand lay-up techniques. The influences of the OPS nanoparticles loading in the natural fibers reinforced polyester hybrid composites were determined by analyzing physical, mechanical, morphological, and thermal properties of the composites. Results showed that the incorporation of the OPS nanoparticles into the hybrid composites enhanced the composite properties. Further, the natural fibers reinforced polyester hybrid composite had the highest physical, mechanical, morphological, and thermal characteristics at 3 wt.% OPS nanoparticles loading.     

Influence of nanosize clay platelets on the mechanical properties of glass fiber reinforced polyester composites

Glass fiber reinforced polyester composite and hybrid nanoclay-fiber reinforced composites were prepared by hand lay-up process. The mechanical behavior of these materials and the changes as a result of the incorporation of both nanosize clay and glass fibers were investigated. Composites were prepared with a glass fibre content of 25 vol%. The proportion of the nanosize clay platelets was varied from 0.5 to 2.5 vol%. Hybrid clay-fiber reinforced polyester composite posses better tensile, flexural, impact, and barrier properties. Hybrid clay-fiber reinforced polyester composites also posses better shear strength, storage modulus, and glass transition temperature. The optimum properties were found to be with the hybrid laminates containing 1.5 vol% nanosize clay.     

Chemical treatment of sisal fiber using alkali and clay method

In this study the chemical treatment of sisal fiber using the combined alkali (NaOH) and clay is discussed. The purpose of this fiber treatment is to improve the fiber–matrix compatibility, interface strength, mechanical, thermal and water barrier properties. The phase change due to chemical treatment of raw sisal fiber was examined by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) methods. The result shows the presence of about 20 wt.% clays in NaOH–clay treated sisal fiber with 2.6× reduced water uptake and also with improved mechanical and thermal properties. Subsequently the treated and untreated fibers were reinforced in polypropylene (PP) matrix and the mechanical and thermal properties were examined. The result indicates that the fiber–matrix interface strength, adhesion, glass transition temperature and tensile properties of composites were improved in NaOH–clay treated fiber composites.     

Effect of glass hybridization and staking sequence on mechanical behaviour of interply coir–glass hybrid laminate

The interest in fibre-reinforced polymer composites is growing rapidly due to its high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost, and low density. The development of composite materials based on the reinforcement of two or more fibre types in a matrix leads to the production of hybrid composites. In the present work, woven coir–glass hybrid polyester composites were developed and their mechanical properties were evaluated for different stacking sequences. Scanning electron micrographs of fractured surfaces were used for a qualitative evaluation of interfacial properties of woven coir–glass hybrid polyester composites. These results indicated that coir–glass hybrid composites offered the merits of both natural and synthetic fibres.     

活性橡胶与蒙脱土复合增强不饱和聚酯/玻璃纤维复合材料的结构与性能

制备了丙烯酸酯封端聚氨酯(ATPU)和改性蒙脱土(OMMT)复合增强不饱和聚酯/玻璃纤维复合材料。通过扫描电子显微镜(SEM)等研究了ATPU和OMMT的复合对不饱和聚酯/玻璃纤维复合材料的力学性能、热变形温度和结构的影响。结果表明,丙烯酸酯封端聚氨酯与改性蒙脱土的复合具有协同效应,可以大大提高不饱和聚酯/玻璃纤维复合材料的冲击强度和拉伸强度,并使复合材料的弯曲强度、巴氏硬度和热变形温度略有提高;丙烯酸酯封端聚氨酯与改性蒙脱土的复合还提高了聚合物基体与玻璃纤维的界面粘合强度。     

Special manufacturing and characteristics of basalt fiber reinforced hybrid polypropylene composites: Mechanical properties and acoustic emission study

Basalt fiber reinforced, polypropylene matrix hybrid composites were manufactured in the process of carding, needle-punching and pressing. Hemp, glass and carbon fibers were applied besides basalt fiber in these composites. In order to achieve a sufficient interfacial adhesion, the fibers were treated with the reaction mixture of maleic acid anhydride and sunflower oil. The hybrid effect in these composites was examined as a function of fiber content and fiber combination. The strength properties of hybrid composites improved owing to surface treatment and this was proven by mechanical tests and microscopic analysis, as well. Acoustic emission methods revealed that there is a correlation between the physical parameters of sound waves that occurred during failure and the mechanical properties.     

Polyamide-6/vegetal fiber composite prepared by extrusion and injection molding

The interest for the use of vegetal fibers as polymers reinforcement has recently increased because of their unique environmental and technological advantages. This work evaluated the use of Curauá fibers in polyamide-6 composites aiming at glass fiber replacement. Fiber content of 20, 30 or 40 wt% and fiber lengths of 0.1 or 10 mm were studied. Fibers were treated with N₂ plasma or washed with NaOH solution, to improve their adhesion to PA-6. Samples with 20 wt% of short or long fibers, with or without pre-treatment, were compounded in two different co-rotating intermeshing twin-screw extruders. These samples were submitted to mechanical and thermal tests. In conclusion, non-dried raw materials improved fiber/matrix interfacial adhesion. Tensile and flexural properties of this composite are better than unfilled, but lower than glass fiber reinforced polyamide-6. However, its impact resistance and heat deflection temperature are similar to the glass fiber reinforced polyamide-6 and its lower density, enable it to replace this latter in specific non-critical applications.     

Carbon and glass hierarchical fibers: Influence of carbon nanotubes on tensile,flexural and impact properties of short fiber reinforced composites

Dense carbon nanotubes (CNTs) were grown uniformly on the surface of carbon fibers and glass fibers to create hierarchical fibers by use of floating catalyst chemical vapor deposition. Morphologies of the CNTs were investigated using scanning electronic microscope (SEM) and transmission electron microscope (TEM). Larger diameter dimension and distinct growing mechanism of nanotubes on glass fiber were revealed. Short carbon and glass fiber reinforced polypropylene composites were fabricated using the hierarchical fibers and compared with composites made using neat fibers. Tensile, flexural and impact properties of the composites were measured, which showed evident enhancement in all mechanical properties compared to neat short fiber composites. SEM micrographs of composite fracture surface demonstrated improved adhesion between CNT-coated fiber and the matrix. The enhanced mechanical properties of short fiber composites was attributed to the synergistic effects of CNTs in improving fiber–matrix interfacial properties as well as the CNTs acting as supplemental reinforcement in short fiber-composites.     

Multi-scale study of the adhesion between flax fibers and biobased thermoset matrices

The environmental impact of composite materials made with a thermoset matrix can be reduced in two ways. First, glass fibers can be replaced by natural fibers. Second, petrochemical components from the matrix can be replaced by biobased renewable equivalents. The quality of the interface between the matrix and the fibers has a strong influence on the composite mechanical properties. In this study, tensile performances of flax fibers and commercially partly biobased epoxy and polyester matrices have been investigated and corresponding unidirectional composites were elaborated. Their mechanical performances are in accordance with fiber and matrices properties, taking into account fiber dispersion. Then, at the microscopic scale, the debonding test was used; a great adhesion between flax fiber and thermoset matrices was highlighted. Finally, tensile tests on ±45° laminates were carried out to create an in-plane shear at the macroscopic scale. Interestingly, the results obtained at the macroscopic scale are well correlated to the ones given by the debonding test at the microscopic scale.     

Analysis of effective elastic modulus for multiphased hybrid composites

Short fiber reinforced composites inherently have fiber length distribution (FLD) and fiber orientation distribution (FOD), which are important factors in determining mechanical properties of the composites. Since the internal structure has a direct effect on the mechanical properties of the composites, a Micro-CT was used to observe the three dimensional structure of fibers in the composites and to acquire FLD and FOD. It was successful to investigate FLD, FOD, and fiber orientation states and to predict the elastic modulus of the hybrid system. Since hybrid composites used in this study consist of three phases of particles, glass fibers, and matrix, theoretical hybrid modeling is required to consider reinforcing effects of both particles and glass fibers. Interaction between the particles and matrix was considered by using a perturbed stress–strain theory, the Tandon–Weng model. In addition, the laminating analogy approach (LAA) was used to predict the overall elastic modulus of the composite. Theoretical prediction of hybrid moduli indicated that there was a possibility of poor adhesion between glass fibers and matrix. The poor interfacial adhesion was confirmed by morphological experiments. This theoretical and experimental platform is expected to provide more insightful understanding on any kinds of multiphased hybrid composites.     

Effects of carbon nanofibers (CNFs) on thermal and interlaminar shear responses of E-glass/polyester composites

A high intensity ultrasonic liquid processor was used to infuse 0.1–0.4 wt.% carbon nanofibers (CNFs) into the polyester matrix which was then mixed with a catalyst using a high speed mechanical agitator. Both conventional and nanophased glass fiber reinforced polyester composites (GRPCs) were fabricated using the vacuum assisted resin transfer molding (VARTM) process. Scanning electron microscope (SEM) revealed best dispersion of CNFs in the 0.2 wt.% CNF-loaded resin. Proper resin flow and impregnation of the glass fibers were also seen in the SEM micrographs. DMA studies exhibited about 49.5% increase in the storage modulus and about 3 °C increase in the glass transition temperature (T_g) due to the incorporation of CNFs into the GRPC. TMA studies also showed better thermal stability and lower thermal expansion in the CNF-loaded GRPC. CNF-loaded GRPC showed higher ILSS due to better interfacial bonding between the fiber and matrix due to the presence of CNFs. Fracture morphology studied by both optical microscope (OM) and SEM revealed better interfacial bonding in the CNF-loaded GRPC.     

Study of chemical and mechanical properties of Dharbai fiber reinforced polyester composites

This investigation is focused on identifying a new variety of natural fiber (Dharbai fiber) for reinforcement in polymer matrix composites. An investigation on extraction procedure of Dharbai fibers has been undertaken. The chemical properties of Dharbai fibers were determined experimentally as per TAPPI standards. The FT-IR Spectroscopy was used to study the chemical structure of Dharbai fibers and the tensile properties of these fibers were studied using single filament test. The fibers extracted were reinforced in polyester matrix by varying the fabrication parameters namely fiber weight content (%) and fiber length (mm). The effect of fiber weight content and fiber length on the mechanical properties of Dharbai fiber-polyester composites were evaluated as per ASTM standards. Scanning electron microscope was used to characterize the interfacial bonding between Dharbai fibers and polyester matrix. This study confirmed that, the Dharbai fibers could be used as an effective reinforcement material for making low load bearing polymer composites.     

Thermal behavior of E-glass fiber-reinforced unsaturated polyester composites

The aim of this work is to study the behavior of E-glass fiber unsaturated polyester composites, subjected to moderate and high temperatures. The obtained results show that the chemical, physical and mechanical properties of the resin and the composite change with the rise of the temperature. A thermogravimetric analysis (TGA) revealed that the thermal degradation of the composite occurs in two steps: the first between 130 and 200 °C and the second between 250 and 440 °C.The characterization of the resin and the composite, after heating, revealed that at moderate temperatures (lower than 100 °C) an improvement of the properties of materials is observed. For high temperatures but lower than the temperature of decomposition (Td), the mechanical strength of the resin does seem to be very affected, even improved for certain cases. For these temperatures, the composite presents some fractures of the fiber–matrix interfaces, which causes losses in strength and ductility.When the temperature reaches the temperature of decomposition (Td), a fall of the mechanical properties was recorded for both resin and composite.     

Degradation of polymer-based composites in corrosive media: experimental attempts towards underlying mechanisms

In spite of previous studies on the corrosion behavior of glass-fiber-reinforced plastic composites, it is necessary to establish the relationship between the degradation occurring at the fiber/matrix interface of these composites and their mechanical performance. Here we report a series of experimental-based investigations to assess the issue. For this purpose, glass fiber/polyester samples were immersed in HCl (10% wt.) at three different temperatures, 25°C, 50°C, and 70°C. The effects on the bending, tensile and hardness properties, changes in the appearance, and microstructural analyses were evaluated over periods of 1 to 4 weeks of immersion. The results indicated that the bending strength, ultimate tensile strength, Young’s modulus and hardness of the samples decreased when exposed to longer exposure duration and/or higher temperature. The polyester degradation was demonstrated by increased surface roughness, cracks and changes in the solution color. In addition, visual inspection of tensile test fracture surfaces and SEM images of the broken sections revealed the drastic corrosion of the fibers and the interface. Finally, atomic absorption spectroscopy (AAS) was carried out, indicating the occurrence of ion exchange reactions. Our results revealed that the underlying mechanism affecting the corrosion happens in the interfacial zone of these composites.

     

玻璃/苎麻纤维混杂复合材料力学性能研究

混杂纤维增强复合材料由于可以综合利用各种纤维的优点,极大的提高了复合材料的性能,拓展了复合材料的适用范围。本文采用玻璃纤维和苎麻纤维混杂酚醛树脂制备复合材料,研究了复合材料混杂比和铺层顺序对混杂纤维复合材料力学性能的影响。从结果可以看出,玻璃纤维和苎麻纤维的不同比例对混杂复合材料的力学性能有着显著的影响,而采用玻璃纤维作为芯层的时候可以获得较好的拉伸性能,采用苎麻纤维作为芯层的时候可以获得较好的弯曲和剪切性能。     

Mechanical and thermal properties of polypropylene reinforced with Alfa fiber under different chemical treatment

The interest in using natural fibers as reinforcement for thermoplastic polymers was attracted several studies covering both material science and green technology. The use of plant fiber requires the issue of compatibility between matrix and fibers. This study treat the effect of chemical modification (alkali treatment, etherification treatment and esterification treatment) on the Alfa fiber surface, and its impact on mechanical and thermal properties of composites. To this end, the percentage of fibers was fixed at (20 wt.%), and to evaluate the effect of each chemical modification in Alfa reinforced polypropylene (PP), based on the mechanical and thermal properties of composites. Composites containing chemically modified Alfa fibers were found to possess improved mechanical and thermal properties when compared to non-treated composite. The highest improvement in Young’s modulus was observed with esterified fibers, with a 35% increase. Thermal stability is best increased using etherification-treated fiber, with gains in the temperature up to 80 °C.     

Influence of filler/reinforcing agent and post-curing on the flexural properties of woven and unidirectional glass fiber-reinforced composites

The aim of this study is to investigate the reinforcing effect of woven and unidirectional glass fibers and the effect of post-curing on the flexural strength and flexural modulus of glass fiber-reinforced composites. A series of composites containing 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)-phenyl]propane and triethyleneglycol dimethacrylate matrices and different reinforcements of unidirectional or woven glass fibers were prepared. The samples, 25 × 2 × 2 mm, were cured with a halogen curing lamp, followed by additional curing by thermal treatment at 135 ± 5 °C temperature and 60 psi pressure. Samples were tested before and after post-curing in order to determine the flexural strength and flexural modulus. The degree of reinforcement with glass fibers was varied between 14 and 57 wt% or 7.64 and 38.44 vol% by changing the number of unidirectional bundles or woven glass fiber bands in the composites, respectively. The obtained flexural strength values were in the range of 95.20–552.31 Mpa; the flexural modulus ranged between 2.17 and 14.7 GPa. The highest flexural strength and flexural modulus values were recorded for samples with unidirectional glass fibers. The mechanical qualities of the glass fibers-reinforced composites increased after post-curing treatment. Increasing of the glass fiber amount in the experimental composites improves both flexural strength and modulus. SEM micrographs of fractured composites indicate a strong interfacial interaction between the glass fibers and the polymer matrix.     

Influence of short bamboo/glass fiber on the thermal, dynamic mechanical and rheological properties of polypropylene hybrid composites

The present article summarizes the development of polypropylene-bamboo/glass fiber reinforced hybrid composites (BGRP) using an intermeshing counter rotating twin screw extruder followed by injection molding. Maleic anhydride grafted polypropylene (MAPP) has been used as a coupling agent to improve the interfacial interaction between the fibers and matrix. The crystallization and melting behavior were investigated employing differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) indicates an increase in thermal stability of the matrix polymer with incorporation of bamboo and glass fibers, confirming the effect of hybridization and efficient fiber matrix interfacial adhesion. The dynamic mechanical analysis (DMA) showed an increase in storage modulus (E′) indicating higher stiffness in case of hybrid composites as compared with untreated composites and virgin matrix. The rheological behavior of the hybrid composites has also been studied using time–temperature superposition (TTS) principle and corresponding viscoelastic master curves have been constructed.