The Mechanical Properties and Chemical Resistance of Short Glass-Fiber-Reinforced Epoxy Composites

ABSTRACT

Epoxy–short glass fiber composites were prepared by directly blending two-pack system of Araldite (CY-230) and hardner (HY-951) with short glass fibers. The short glass fiber content was varied from 2% to 10% by weight of the total matrix. These composites were then characterized for morphology using scanning electron microscopy, mechanical properties, that is, tensile and flexural properties and resistance toward various chemicals. The epoxy-glass fiber composites showed improved tensile and flexural properties but increased dispersion among the properties with increasing fiber content. Several reasons to explain these effects in terms of reinforcing mechanisms were discussed. These composites were stable in most chemicals but were completely destroyed in concentrated sulfuric acid, nitric acid, and pyridine.     

Characterization of Fracture in Fiber-Reinforced Ceramic Composites under Shear loading

This study developed a test technique for mode II fracture testing of a fiber-reinforced ceramic composite. This method employed a small, straight-notched, precracked, end-notched flexure specimen subjected to three-point bending. This method was demonstrated by measuring the mode II critical strain energy release rate, G _{II c} of a fiber-reinforced glass-ceramic composite at room temperature.     

Fabrication and Physico-Chemical Properties of High-Performance Pine Needles/Green Polymer Composites

Natural cellulosic pine needles were used in long fiber form as a new, potential reinforcement to fabricate green composites using the compression-molding technique. Mechanical and physico-chemical properties of green composites have been investigated as a function of fiber loading in order to assess their applicability in everyday life. The green composites fabricated showed a universal trend of increase in properties with fiber loading up to 30% and beyond this loading these properties decrease. Fiber/matrix interaction between the polymer and reinforcement has been analyzed from the mechanical and morphological studies, which reveal the impact of good interfacial compatibility.     

天然植物纤维增强环氧树脂复合材料研究进展

从天然植物纤维及其改性方法、基体环氧树脂及特性和复合材料的成型方法等方面综述了近年来国内外利用天然植物纤维增强环氧树脂复合材料的研究进展。     

Tensile Properties of Arenga pinnata Fiber-Reinforced Epoxy Composites

The aim of this study is to determine the tensile properties of Arenga pinnata fiber as a natural fiber and epoxy resin as a matrix. The Arenga pinnata fibers were mixed with epoxy resin at the various fiber weight percentages of 10%, 15%, and 20% Arenga pinnata fiber and with different fiber orientations such as long random, chopped random, and woven roving. Hand lay-up processes in this experiments were to produce specimen test with the curing time for the composite plates is in the room temperature (25–30°C). Results from the tensile tests of Arenga pinnata fiber reinforced epoxy composite are that the 10 wt.% woven roving Arenga pinnata fiber showed the highest value for maximum tensile properties. The tensile strength and Young's modulus values for 10 wt.% of woven roving Arenga pinnata fiber composite are 51.725 MPa and 1255.825 MPa, respectively. The results above indicate that the woven roving Arenga pinnata fiber has a better bonding between its fiber and matrix compared to long random Arenga pinnata fiber and chopped random Arenga pinnata fiber. Scanning electron microscopy (SEM) tests were carried out after tensile tests to observe the interface of fiber and matrix adhesion.     

Lignin Epoxy Composites: Preparation,Morphology, and Mechanical Properties

A novel route to lignin epoxy composites is developed through covalent incorporation of depolymerized lignin epoxide into amine‐cured epoxy matrix. The partially depolymerized lignin is first epoxidized with epichlorohydrin and the resultant depolymerized lignin epoxide shows decreased solubility in common organic solvents. When dispersed in epoxy matrix and cured, the depolymerized lignin epoxide is integrated into epoxy networks in the form of submicron aggregates. The resulting lignin epoxy composites show improved mechanical properties compared with neat epoxy. At a loading content of 1.0 wt% of degraded lignin epoxide, the Young's modulus and the critical stress intensity factor (K_IC) of the composite increase by 10% and 25%, respectively, in comparison with those of neat epoxy, while the glass transition temperature is little changed. This method presents a promising way to convert wasteful lignin to an alternative epoxy monomer and effective additive in epoxy composites.

     

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.     

Preparation and Properties of Natural Sand Particles Reinforced Epoxy Composites

An epoxy composite using Cancun natural hydrophobic sand particle as filler material was fabricated in this study. Three point bending tests demonstrated an enhancement of 7.5 and 8.7% in flexural strength and flexural modulus, respectively, of epoxy composite containing 1 wt.‐% sand particles without any chemical treatment involved, compared to the pristine epoxy. Scanning electron microscopy (SEM) studies revealed that the fracture toughness of the epoxy matrix was enhanced owing to the presence of sand particles in an epoxy/sand composite. Through dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) methods, it was found that the storage modulus (E′), glass transition temperature (T_g) and dimensional stability of the sand particles/epoxy composites were increased compared to the pristine epoxy. The friction behavior of epoxy/sand system reflected that the microstructure of epoxy composites was steady. These experimental results suggest that Cancun sand, as a freshly found natural micron porous material, may find promising applications in composite materials.

     

Experimental assessment of the improved properties during aging of flax/glass hybrid composite laminates for marine applications

The investigation for natural fibers composites in terms of performance, durability, and environmental impact for structural applications in marine environments is a relevant challenge in scientific and industrial field. On this context, the aim of this work is to assess the durability and mechanical stability in severe environment of epoxy/glass–flax hybrid composites. For the sake of comparison, also full flax and glass epoxy composites were investigated. All samples were exposed to salt–fog environmental conditions up to 60 aging days. Wettability behavior during time was compared with water uptake evolution to assess water sensitivity of hybrid composite configurations. Moreover, quasi-static flexural and dynamic mechanical analysis were carried to evaluate as aging conditions, laminate configuration influence the surface and mechanical performances stability of the hybrid composites. The addition of glass fibers on flax laminate allows to enhance both flexural strength by 90%, and modulus by 128%, even if these properties are lower than those of full glass laminates. The results evidenced that the hybridization of flax fibers with glass ones is a practical approach to enhance the aging durability of epoxy/flax composite laminates in marine environmental conditions, obtaining a suitable compromise among environmental impact, mechanical properties, aging resistance, and costs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47203.     

Fabrication and Characterization of H. sabdariffa Fiber-Reinforced Green Polymer Composites

Present work is concerned with the evaluation of the mechanical properties of compression molded Hibiscus sabdariffa (HS) fibre-reinforced Urea-Formaldehyde (UF) matrix based green polymer composites. Reinforcing of the Urea-Formaldehyde (UF) resin with Hibiscus sabdariffa (HS) fibre was accomplished in the form of short fibre (3 mm). It has been observed that mechanical properties of UF matrix increases with fibre loading and then decreases for higher loading (beyond 30%). Morphological and thermal studies of the matrix, fibre and short fibre-reinforced (SF-Rnf) green composites have also been carried out.     

Effect of Interfaces on the Properties of Fiber-Reinforced Ceramics

The mechanical properties of a series of six fiber-reinforced ceramics and glasses have been evaluated with the objective of critically assessing present understanding. A major parallel theme has been the characterization of the interface and an assessment of the thermomechanical properties of the interfaces as they relate to composite behavior. The results establish that the available mechanical property models correlate well with experiments, provided that independent measurements are made of the residual stress, the interface sliding stress, and the in situ strength properties of the fibers. In addition, trends in the sliding stress are found to be qualitatively consistent with those expected for sliding along debonded surfaces.     

Synthesis and Characterization of Grewia Optiva Fiber-reinforced PF-based Composites

In this article, the synthesis of natural fiber-reinforced phenol-formaldehyde (PF) resin matrix-based polymer composites has been reported. Initially the phenol-formaldehyde resin was prepared by varying the concentration of formaldehyde with a fixed weight of phenol. Polymeric resins of different P:F ratios were subjected for optimization of their mechanical properties. The sample ratio of 1:1.5 (P:F) was found to possess maximum mechanical strength. Then reinforcing of this optimized resin was done by taking different ratios of Grewia optiva fiber in particle form (200 μ) to prepare green polymer composites. The polymer composite materials thus prepared were subjected for evaluation of their mechanical properties such as tensile, compressive, flexural, and wear resistance. It has been observed that optimum mechanical properties were obtained for fiber loading of 30%. Further, the mechanical strength of the composites has been found to be higher than the parent phenol-formaldehyde resin matrix. The morphological and thermal properties of the composites have also been studied.     

Softwood Distillate as a Bio-Based Additive in Wood-Plastic Composites

The possibility of using softwood distillate as a bio-based additive or filler in wood-plastic composites (WPCs) was studied by adding various amounts (1–20 wt%) of distillate to a commercial WPC consisting of thermally treated sawdust in a polypropylene (PP) matrix. Softwood distillate was obtained as a secondary product from industrial ThermoWood® processing and it was further processed in the laboratory. The addition of softwood distillate significantly enhanced the mechanical properties of WPC when the distillate content was 2 wt%; tensile strength increased by 5%, tensile modulus by 3%, flexural strength by 3%, and modulus of elasticity by almost 2% compared with the unmodified WPC. In addition, a considerable decrease (over 16%) in water absorption was observed on distillate addition. Proton-transfer-reaction time-of-flight mass-spectrometry (PTR-TOF-MS) analyses revealed that the addition of softwood distillate increased release rates of volatile organic compounds (VOCs) in general, and that the odor of acetaldehyde and guaiacol is detectable in several WPCs. Overall, softwood distillate had positive effects on this particular WPC.     

Effect of the Fiber Size on the Physicochemical and Mechanical Properties of Composites of Epoxy and Date Palm Tree Fibers

Lignocellulosic fibers from date palm trees were employed to reinforce an epoxy matrix. Two fiber sizes were used, with the length and diameter in the range of 20–30 and 1.5–3 mm, respectively, for the so‐called long fibers, and in the range of 5–15 and 0.25–0.75 mm, respectively, for the so‐called short fibers. The morphologies of the resulting composites, as well as their thermal, mechanical, and water sorption properties were evaluated. Strong interactions between both components and etherification reactions may occur between the hydroxyl groups of the fibers and the epoxy groups of the epoxy‐amine reactive mixture. These effects are emphasized when decreasing the size of the fibers.

     

玻璃纤维/溴化环氧乙烯基酯复合材料的加速光老化研究

研究了玻璃纤维增强溴化环氧乙烯基酯树脂复合材料(GFRC)光老化前后力学性能及其变化规律;用SEM和XPS对GFRC的表面微观形貌及元素变化进行检测分析;FTIR和同步热分析用来研究树脂光老化过程中的分子结构的变化规律和高温分解情况。结果表明,加速光老化之后GFRC的力学性能变化不大,有较好的拉伸强度、弯曲强度和压缩强度保留率;加速光老化过程中GFRC表面的树脂发生较明显的变化,出现了颜色变深,树脂脱落等老化现象;由于玻璃纤维的存在阻止了GFRC内部树脂基体的进一步老化。     

微波技术在环氧树脂及其复合材料中的应用

论述了近年来微波固化技术在环氧树脂及其复合材料固化中的应用,重点比较了微波固化与传统热固化后环氧树脂及其复合材料的力学性能、热性能和粘结强度的变化,并对环氧树脂复合材料微波固化的研究进行了展望。     

茶多酚改性天然胶乳复合材料的制备及性能研究

以多羟基结构的茶多酚作界面改性剂,制备了埃洛石纳米管/天然胶乳复合材料及二氧化硅/天然胶乳复合材料,研究了茶多酚对复合材料界面作用及力学性能的影响。结果表明,茶多酚分别能与埃洛石纳米管和二氧化硅形成氢键,改善了填料与橡胶基体间的界面作用。茶多酚改性天然胶乳复合材料的力学性能显著提高,其原因归因于复合材料界面状态的改善。     

海军舰炮弹药用碳布增强环氧复合材料热老化寿命预测

研究了热老化对海军舰炮弹药用碳布增强环氧复合材料力学性能的影响,并利用回归分析方法对复合材料热老化寿命进行了预测。结果表明,碳布增强环氧复合材料分别在温度110,120,130,140℃热空气条件下老化2000 h,材料的各项力学性能总体呈下降趋势,但降幅很小,甚至在整个试验过程中会出现性能升高的情况,说明材料具有优异的力学性能。以90%作为材料失效判据点,碳布增强环氧树脂基复合材料常温贮存条件下贮存寿命为20年。     

Effect of Bio-Based Cobalt Alginate on the Fire Safety and Mechanical Properties for Epoxy Resin

There is a growing demand to develop epoxy resins (EP) with smoke suppression as well as satisfactory flame retardancy. Herein, bio-based cobalt alginate is successfully fabricated and incorporated into EP to prepare EP/Cobalt Alginate composites with better fire safety performance. The addition of cobalt alginate reduces the thermal-decomposition rate, temperature at maximum weight-loss rate of EP, whereas obviously improves the thermal stabilities at a higher temperature range. Furthermore, the addition of cobalt alginate substantially reduces the fire hazard of EP, resulting in 56.2% reduction in peak heat release rate, as well as 17.8% and 56.3% reduction in total smoke production and peak smoke production rate, respectively, compared with EP matrix. Moreover, the presence of cobalt alginate increases smoke-suppressant properties, according to the smoke density test. Additionally, the incorporation of cobalt alginate has no obviously destructive effect on the mechanical properties of EP, while EP/Cobalt Alginate-3 exhibits a 27.0% improvement in impact strength. In prospective, this study may provide a significant method for producing eco-friendly flame retardant EP.     

Natural rubber composites reinforced with sisal/oil palm hybrid fibers: Tensile and cure characteristics

Natural rubber was reinforced with untreated sisal and oil palm fibers chopped to different fiber lengths. The influence of fiber length on the mechanical properties of the hybrid composites was determined. Increasing the fiber length resulted in a decrease in the properties. The effects of concentration on the rubber composites reinforced with sisal/oil palm hybrid fibers were studied. Increasing the concentration of fibers resulted in a reduction in the tensile strength properties and tear strength but an increase in the modulus of the composites. Fiber breakage analysis was evaluated. The vulcanization parameters, processability characteristics, and stress–strain properties of these composites were analyzed. The extent of fiber alignment and the strength of the fiber–rubber interface adhesion were analyzed from the anisotropic swelling measurements. Scanning electron microscopy studies were performed to analyze the fiber/matrix interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2305–2312, 2004