改性芳纶纬编增强体复合材料力学性能的研究

为探讨芳纶纬编增强体复合材料的力学性能,以对位芳纶为原料,采用LiCl/无水乙醇溶液对芳纶表面进行改性处理,设计并编织1+1满针罗纹和罗纹空气层2种组织织物增强体,以E-51环氧树脂为基体,应用手糊成型技术制备芳纶纬编增强体平板复合材料。采用YG026D型电子织物强力机对制备的芳纶纬编增强体复合平板材料的经纬向拉伸、弯曲、压缩以及层间剪切性能进行测定。结果显示:经LiCl/无水乙醇络合溶液处理的芳纶纬编增强体复合材料的各项力学性能均有所提高,且经向的各项力学性能优于纬向。在拉伸、弯曲性能方面,罗纹空气层芳纶纬编增强体平板复合材料优于1+1满针罗纹芳纶纬编增强体复合材料。     

Comparison of mechanical and ballistic performance of composite laminates produced from single‐layer and double‐layer interlocked woven structures

Textile structures have become quite popular as reinforcement materials in composite laminates due to their high impact‐damage tolerance and energy absorption ability. The impact performance of textile composites is not only affected by the type of fiber/matrix but also by the fabric structure used as reinforcement. The aim of this study was to compare the mechanical and ballistic performance of composite laminates reinforced with single‐layer and double‐layer interlocked woven fabrics. Kevlar^®−29 multifilament yarn was used for preparation of all the fabric structures and epoxy resin was used as the matrix system. The composites were produced using a hand lay‐up method, followed by compression molding. The mechanical and ballistic performance of composites reinforced with single‐layer and double‐layer interlocked woven fabrics was investigated in this study. The energy absorption and mechanical failure behavior of composites during the impact event were found to be strongly affected by the weave design of the reinforcement. The composites reinforced with double‐layer interlocked woven fabrics were found to perform better than those comprising single‐layer fabrics in terms of impact energy absorption and mechanical failure. POLYM. COMPOS., 35:1583–1591, 2014. © 2013 Society of Plastics Engineers     

Impact behavior of aramid fiber/glass fiber hybrid composites: The effect of stacking sequence

Aramid fiber/glass fiber hybrid composites were prepared to examine the effect of stacking sequence on the impact behavior of thin laminates. The effect of position of the aramid layer on the impact properties of hybrid composites was investigated using driven dart impact tester. The delamination area and fracture surface of hybrid composites were analyzed for correlation with impact energy. The addition of glass layer to aramid layer reduced the impact resistance of hybrid composite due to the restriction in the deformation of aramid layer. The position of aramid layer resulted in variations in the impact behavior of hybrid composites. When the aramid layer was at the impacted surface, the composite exhibited a higher impact energy. This was attributed to the fact that the flexible layer at the impacted surface in thin laminates can experience larger deformation. In three‐layer composites, the aramid fiber‐reinforced composite ( AAA ) exhibited the highest total impact energy due to high impact energy per delamination area (1EDA) in spite of low delamination area. Aramid fiber and glass fiber‐reinforced composites showed a different impact behavior according to the change of thickness. This was attributed to the difference in the energy absorption at interface between laminae.     

Maxwell Model Parameters for Single Filaments of Aramid,Glass, and Basalt Fibers

Fibre Chemistry - Maxwell model parameters for stretching of single filaments of Twaron® aramid fiber (Japan), Advantex® glass fiber, and basalt fiber are given. Measurements were made...     

Investigation of the high velocity impact behavior of nanocomposites

In this article, the ballistic behavior of the glass/epoxy/nanoclay hybrid nanocomposites is studied. The fiber glass used is a plain weave 200 g/m², while the nanoclay is an organically modified montmorillonite nanoclay (Closite 30B). The epoxy resin system is made of Epon 828 as the epoxy prepolymer and Jeffamine D‐400 as the curing agent. 0, 3, 5, 7, and 10 wt% of nanoclay particles are dispersed in the epoxy resin. Ballistic tests are performed using flat‐ended projectiles in impact velocities 134 m/s and 169 m/s. The results show that the energy absorption capability and mechanical properties of the composite can be significantly enhanced by adding nanoparticles. When the impact velocity is 134 m/s, near than the ballistic limit, the most increase in the energy absorption capability is observed in 3 wt% nanoclay while with the impact velocity 169 m/s, beyond the ballistic limit, the highest increase is observed in 10 wt% nanoclay. POLYM. COMPOS., 37:1173–1179, 2016. © 2014 Society of Plastics Engineers     

Comparison of mechanical properties of epoxy composites reinforced with stitched glass and carbon fabrics: Characterization of mechanical anisotropy in composites and investigation on the interaction between fiber and epoxy matrix

The primary purpose of the study is to evaluate and compare the mechanical properties of epoxy‐based composites having different fiber reinforcements. Glass and carbon fiber composite laminates were manufactured by vacuum infusion of epoxy resin into two commonly used noncrimp stitched fabric (NCF) types: unidirectional and biaxial fabrics. The effects of geometric variables on composite structural integrity and strength were illustrated. Hence, tensile and three‐point bending flexural tests were conducted up to failure on specimens strengthened with different layouts of fibrous plies in NCF. In this article, an important practical problem in fibrous composites, interlaminar shear strength as measured in short beam shear test, is discussed. The fabric composites were tested in three directions: at 0°, 45°, and 90°. In addition to the extensive efforts in elucidating the variation in the mechanical properties of noncrimp glass and carbon fabric reinforced laminates, the work presented here focuses, also, on the type of interactions that are established between fiber and epoxy matrix. The experiments, in conjunction with scanning electron photomicrographs of fractured surfaces of composites, were interpreted in an attempt to explain the failure mechanisms in the composite laminates broken in tension. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Interfacial studies on the surface modified aramid fiber reinforced epoxy composites

In this work, solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of aramid fiber. The effect of chemical treatment on aramid fiber has been studied in a composite system. The surface characteristics of aramid fibers were characterized by Fourier transform infrared spectroscopy (FTIR). The interfacial properties of aramid/epoxy composites were investigated by means of the single fiber pull‐out tests. The mechanical properties of the aramid/epoxy composites were studied by interlaminar shear strength (ILSS). As a result, it was found that RES surface treatment is superior to ECP grafting treatment in promoting the interfacial adhesion between aramid fiber and epoxy matrix, resulting in the improved mechanical properties of the composites. Meanwhile, the tensile strengths of single fibers were almost not affected by RES treatment. This was probably due to the presence of reactive functional groups on the aramid fiber surface, leading to an increment of interfacial binding force between fibers and matrix in a composite system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4165–4170, 2006     

Novel polymer‐ceramic composites for protection against ballistic fragments

For the first time, internally reinforced aggregate polymer ceramic composites were evaluated against fragment simulating projectiles (FSPs) of various calibers to investigate their ballistic impact response. Samples were prepared by mechanically mixing B₄C and cBN over a range of ratios and combinations with either thermosetting phenolic or epoxy resin and aramid pulp. Dry mixtures were then molded in a closed die using a heated platen press. The resulting tiles were then mounted as “strike faces” to an aramid backing material using an epoxy resin. Backed targets were tested in a fully instrumented firing range against 5.56 mm FSPs to test ballistic limit. A further series of tests using 7.62, 12.5, and 20 mm FSPs was conducted to examine round deformation across a range of fragments calibers. Round deformations were measured after impact and plotted against shot velocity. It was found that the polymer ceramic composite materials were effective round deformers and, like sintered ceramic strike faces, demonstrated improved ballistic performance at an equivalent areal density and impressive multihit capability. POLYM. COMPOS., 2012. © 2013 Society of Plastics Engineers     

芳纶针织物复合材料力学性能研究

为探究芳纶针织物复合材料的力学性能,用电子织物强力机对平板硫化机制得的芳纶针织物复合材料进行拉伸、弯曲、压缩性能测试,结果表明:芳纶针织物增强复合材料为非脆性破坏;经硅烷偶联剂处理有效地提高了芳纶针织物增强复合材料的抗拉、抗弯、抗压强度;罗纹空气层组织的抗拉、抗弯及抗压性能优于满针罗纹组织。     

Adhesive joints between carbon fiber and aluminum foam reinforced by surface‐treated aramid fibers

Short aramid fibers have been successfully used to reinforce the interface adhesive property between carbon fiber/epoxy composites and aluminum foam, and to form aramid‐fiber “composite adhesive joints.” In this study, to further improve the reinforcing effect of the aramid‐fiber‐reinforced adhesive joints, aramid fibers were ultrasonic treated to conduct different surface conditions. Critical energy release rate of the carbon fiber/aluminum foam sandwich beams with as‐received and treated interfacial aramid fibers were measured to study the influence of the surface treatment on aramid fibers. It was found that reinforcements in critical energy release rate were achieved for all samples with treated aramid fiber as measured under double cantilever beam condition. The interfacial characteristics of the short aramid fibers with different surface condition were investigated and discussed based on scanning electron microscopy observations. It is suggested that advanced bonding between aramid fibers and epoxy resin was conducted after surface treatment, and more energy was therefore absorbed through fiber bridging during crack opening and extension process. POLYM. COMPOS., 36:192–197, 2015. © 2014 Society of Plastics Engineers     

Effect of compressive loading speed and stacking sequence on mechanical characteristics of satin weave E‐glass/epoxy composites

This article experimentally investigated the in‐plane loading speed dependent mechanical properties and failure modes of satin weave E‐glass/epoxy composite laminates [45/−45/0/90]_ns. Two types of E‐glass fabric/epoxy pre‐impregnated tapes were used to manufacture the composite laminates specimens. The low strain rate tests were conducted with an INSTRON™ testing machine, and the high strain rate tests done using a pulse shape modified compressive Split Hopkinson Pressure Bar apparatus. From the experimental result, it was concluded that under different strain rate loading, compressive strength, modulus, and strain at peak stress were rate sensitive. Optical and microscopic photos of the specimens were taken to determine operative failure modes. Within the studied strain rate regimes, the failure mode changed from splitting followed by fiber kink buckling to predominantly delamination and shear fracture as strain rate increases from quasi‐static to high strain rates. Compressive properties and failure modes were severely affected by strain rate, stacking sequence, and fabric material. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers     

Effect of deposited carbon nanotubes on interlaminar properties of carbon fiber‐reinforced epoxy composites using a developed spraying processing

Carbon fiber‐reinforced epoxy composites, with incorporated carboxylic multiwall carbon nanotubes (CNTs), were prepared using vacuum‐assisted resin infusion (VARI) molding, and the in‐plane and out‐of‐plane properties, including mode‐I (G_Ic) and mode‐II (G_IIc) interlaminar fracture toughness, interlaminar shear strength (ILSS), tensile, and flexural properties were measured. A novel spraying technique, which sprays a kind of epoxy resin E20 with high viscosity after spraying the CNTs, was adopted to deposit the CNTs on the surface of carbon fiber fabric. The E20 was used to anchor CNTs on the fabric surface, avoiding that the deposited CNTs were removed by the infusing resin during VARI process. The spraying processing, including spraying amount and spraying sequence, was optimized based on the distribution of CNTs on the fibers. After that, three composite specimen groups were fabricated using different carbon fiber fabrics, including as‐received, CNT‐deposited with E20, and CNT‐deposited without E20. The effects of CNTs on the processing quality and mechanical properties of carbon fiber‐reinforced polymer composites were studied. The experimental results show that all studied laminates have uniform thickness with designed values and no obvious defects form inside the laminates. Compared with the composite without CNTs, depositing CNTs with E20 increases by 24% in the average propagation G_Ic, by 11% in the propagation G_IIc and by 12% in the ILSS, while it preserves the in‐plane mechanical properties, However, depositing CNTs without E20 reduces interlaminar fracture toughness. These phenomena are attributed to the differences in the distribution of CNTs and the fiber/matrix interfacial bonding for different spraying processing. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

机织/针织混合铺层对复合材料力学性能的影响

为使纺织复合材料同时具有机织结构复合材料和针织结构复合材料的综合力学性能,通过混合铺层方式制备机织/针织混合结构复合材料。以芳纶机织平纹织物和针织罗纹织物为增强体,以环氧树脂为基体,调整复合材料中增强体的铺层顺序,利用真空辅助成型技术制备四层层压机织/针织混合结构复合材料。通过对复合材料拉伸性能、弯曲性能和冲击性能的测试,分析混合铺层和铺层顺序对芳纶环氧树脂复合材料力学性能的影响。结果表明,混合铺层和铺层顺序对芳纶环氧树脂复合材料的弯曲强度和冲击强度有较大影响,特别是对罗纹结构复合材料纬向弯曲强度和冲击强度的改善。当采用相同铺层方式,罗纹织物为受力面时,机织/针织混合结构复合材料具有较大弯曲强度和冲击强度。     

混杂比对交织芳纶碳纤维复合材料力学性能的影响

为了分析混杂比对层内混杂复合材料力学性能的影响,利用交织方式制备芳纶碳纤维混杂增强体织物,并通过交织物纬纱系统中芳纶与碳纤维的纱线配置比例调整碳纤维在增强体结构中的混杂比。采用真空辅助成型技术制备层内混杂结构的芳纶碳纤维混杂（ACFH）复合材料,并对复合材料的拉伸性能、弯曲性能和冲击性能进行测试。结果表明,增强体纬向系统中芳纶与碳纤维的不均质性对ACFC复合材料经方向上的拉伸强度起消极作用;混杂比的增加对ACFC复合材料的纬向拉伸破坏和弯曲损伤具有抑制作用;纬向上,ACFC复合材料的拉伸强度最高提高了近6倍,弯曲强度最小增加了4.04倍;芳纶与碳纤维混杂协同作用有利于ACFC复合材料的抗冲击性能改善,且混杂比存在最佳值。     

Preparation of multiscale graphene oxide‐carbon fabric and its effect on mechanical properties of hierarchical epoxy resin composite

Graphene oxide (GO) was used to modify the surface of carbon fiber layers through electrophoretic deposition, forming a multiscale reinforcement fabric. By adjusting the experimental parameters, the resulting GO‐carbon fabric showed productive and homogenous distribution of thin and less‐agglomerate GO platelets on carbon fiber surface, remarkably enlarging the surface area and roughness of carbon fabric. To investigate the effect of GO sheets on composites, GO‐carbon fabric and carbon fabric‐reinforced hierarchical epoxy resin composites were respectively manufactured. Mechanical tests demonstrated that after introducing GO flakes on carbon fabric, both the flexural strength and interlaminar shear strength of composite had achieved an increase, especially the interlaminar shear strength rising by 34%. Through fractography analysis, it was found that in pure carbon fabric‐reinforced epoxy composite, the fiber/matrix debonding fracture mechanism predominated, while after the GO decoration on carbon fiber surface, the composite featured a stronger interfacial bonding, leading to the enhancement in mechanical properties of hierarchical epoxy resin composite. POLYM. COMPOS., 37:1515–1522, 2016. © 2014 Society of Plastics Engineers     

Enzyme‐mediated surface modification of jute and its influence on the properties of jute/epoxy composites

Surface modification of jute fibers is necessary to improve the adhesion and interfacial compatibility between fibers and resin matrix before using fibers in polymer composites. In this study, dodecyl gallate (DG) was enzymatically grafted onto the jute fiber by laccase to endow the fiber with hydrophobicity. A hand lay‐up technique was then adopted to prepare jute/epoxy composites. Contact angle and wetting time measurements showed that the surface hydrophobicity of the jute fabric was increased after the enzymatic graft modification. The water absorption and thickness swelling of the DG‐grafted jute fabric/epoxy composite were lower than those of the other composites. The tensile and dynamic mechanical properties of the jute/epoxy composites were enhanced by the surface modification. Scanning electron microscopy images revealed stronger fiber–matrix adhesion in composites with modified fibers. Therefore, the enzymatic graft modification increased the fiber–matrix interface area. The fiber–matrix adhesion was enhanced, and the mechanical properties of the composites were improved. POLYM. COMPOS., 38:1327–1334, 2017. © 2015 Society of Plastics Engineers     

Effect of thermal aging on microstructures of aramid composites

The effect of thermal aging on aramid composites was assessed in this study. Poly(vinyl butyral)/phenol formaldehyde (PVB/PF) resin was used to prepare the aramid composites, which were programmed at 70, 90, 120, and 150°C for various periods of time up to 2,688 h. The microstructures and aging mechanisms were investigated by dynamical mechanical thermal analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Ballistic limited velocity of composites was determined by 1.1g Fragment projectiles. The results suggest that three microphases exist in the PVB/PF system. Each phase exhibits different aging mechanisms at different aging temperatures. Reduction of ballistic limited velocity was strongly affected by aging conditions. POLYM. COMPOS., 38:252–259, 2017. © 2015 Society of Plastics Engineers     

Flammability testing of flame-retarded epoxy composites and phenolic composites

Flame-retarded epoxy composites and phenolic composites containing fiberglass, aramid (Kevlar® 49), and graphite fiber-reinforcements were tested using the NASA upward flame propagation test, the controlled-atmosphere cone calorimeter test, and the liquid oxygen (LOX) mechanical impact test. The upward flame propagation test showed that phenolic/graphite had the highest flame resistance and epoxy/graphite had the lowest flame resistance. The controlled-atmosphere cone calorimeter was used to investigate the effect of oxygen concentration and fiber reinforcement on the burning behavior of composites. The LOX mechanical impact test showed that epoxy/fiberglass had the lowest ignition resistance and phenolic/aramid had the highest ignition resistance in LOX. The composites containing epoxy resin and/or aramid fiber reinforcement reacted very violently in LOX upon mechanical impact. © 1997 by John Wiley & Sons, Ltd.     

Promising curaua fiber‐reinforced polyester composite for high‐impact ballistic multilayered armor

A typical multilayered armor system (MAS) is composed of a harder front ceramic tile, which is able to erode heavy ammunition, such as the 7.62 mm bullet, followed by a second layer to further reduce the impact energy. Aramid fabric is a common choice for the second layer. In the present work, polyester matrix composites reinforced with 10 to 30 vol% of curaua fibers, despite having much lower strength and stiffness than aramid fabric, displayed similar trauma indentation in a standard clay witness simulating the human body. Impedance matching and scanning electron microscopy analyses suggest effective energy absorption through ceramic fragment capture by curaua composites. Additionally, because of the high cost of aramid fabric, a full MAS with curaua fiber composite is much cheaper than a MAS composed of aramid fabric. Taking into consideration, both the economical and environmental advantages of natural fibers, it is concluded that curaua fiber‐reinforced polyester composite could replace aramid fabric as the second layer in MASs for personal ballistic protection. POLYM. ENG. SCI., 57:947–954, 2017. © 2016 Society of Plastics Engineers     

Multiscale fiber‐reinforced composites prepared by vacuum‐assisted resin transfer molding

Carbon nanotube (CNT)/aramid fiber epoxy composites were produced using a new manufacturing method proposed in this study. The rheological and morphological experiments of the CNT/PEO nanocomposites indicates that the PEO nanocomposites have a good dispersion state of the CNTs. The flexural mechanical properties of the aramid fiber/CNT epoxy composites were measured. The CNTs dispersed in the epoxy resin between the aramid fibers were observed using field emission scanning electron miscroscope (FESEM). It was found that the flexural properties of the multiscale fiber‐reinforced composites were higher than those of aramid fiber/epoxy composites. POLYM. COMPOS., 28:458–461, 2007. © 2007 Society of Plastics Engineers.