Tensile properties of plant fibre‐polymer composites in fire

The structural performance of polymer composites reinforced with plant fibres when exposed to fire was experimentally evaluated and compared against an E‐glass fibre laminate. Fire testing under combined one‐sided radiant heating and static tensile loading revealed that flax, jute, or hemp fibre composites experience more rapid thermal softening and fail within much shorter times than the fibreglass laminate, which is indicative of vastly inferior structural performance in fire. The plant fibre composites soften and fail before the onset of thermal decomposition of the plant fibres and polymer matrix, whereas the E‐glass fibres provide the composite with superior tensile properties to higher temperatures and higher applied tensile stresses. The tensile performance of the three types of plant fibre composites in fire was not identical. When exposed to the same radiant heat flux, the flax fibre composite could withstand higher tensile stresses for longer times than the hemp and jute laminates, which showed similar performance.     

新型耐高温阻燃层压板的研制

以苯酚、甲醛为原料,在催化剂的作用下合成酚醛树脂,然后用硼酸改性得到硼酚醛(FB)树脂.采用FB树脂作为基材树脂制作玻璃布层压板,FB树脂的耐热性比普通酚醛树脂高.FB树脂层压板具有好的耐热、阻燃、机械和电气性能,其阻燃性能达到了UL-94垂直燃烧法V-0级.     

Structural degradation and mechanical fracture of hybrid fabric reinforced composites

This investigation involves the study of accelerated environmental aging in two polymer composite laminates reinforced by hybrid fabrics based on carbon, Kevlar and glass fibers. Composite laminate configurations are defined as a laminate reinforced with E‐glass fiber and Kevlar 49 fiber hybrid fabric (GK) and another laminate reinforced with E‐glass fiber and AS4 carbon fiber hybrid fabric (GC). Both laminates were impregnated with epoxy vinyl ester thermosetting resin (Derakane 470‐300) consisting of four layers. Morphological studies (photo‐oxidation process and structural degradation) of environmental aging were conducted, in addition to comparative studies of the mechanical properties and fracture characteristics under the action of uniaxial tensile and three‐point bending tests in specimens in the original and aged conditions. With respect to uniaxial tensile tests for both laminates, good mechanical performance and little final damage (small loss of properties) was caused by the aging effect. However, for the three‐point bending tests, for both laminates, the influence of aging was slightly higher for all parameters studied. The low structural deterioration in the laminates is attributed to the high performance with the heat of the matrix (Derakane 470‐300) and the characteristics of the hybrid fabric, exhibiting fiber/matrix interface quality. POLYM. ENG. SCI., 56:657–668, 2016. © 2016 Society of Plastics Engineers     

聚碳酸酯在轻型防弹玻璃上的应用研究

研究单层PC、层合PC、PC与有机玻璃层合（AC／PC）、PC与无机玻璃层合（G／PC）以及PC与有机玻璃和无机玻璃混合层合（G／AC／PC）结构的防弹性能，对各种结构的减重效果和应用前景进行了分析和比较。结果表明，所有含PC的层合结构都有减重效果，但层合PC或AC／PC之类的有机结构减重效果的防弹能力远不如G／AC／PC或G／PC结构，G／AC／PC和G／PC结构最适合于轻型防弹玻璃。     

Effect of stacking sequence on the compressive performance of impacted aramid fiber/glass fiber hybrid composite

Aramid fiber/glass fiber hybrid composites were prepared to examine the compressive performance of impacted composites. The effect of stacking sequence and surface treatment on compression after impact (CAI) performance of three‐layer hybrid composites was investigated with respect to delamination area. As the impact velocity increased, the laminates exhibited a significant reduction of compressive strength owing to larger delamination area within laminate. The surface treatment aramid fiber reduced the delamination area and enhanced the resistance to buckling. The strength reduction of laminate AAA was considerable because of wide delaminated region, whereas the residual strength of laminate GGG was not affected by impact energy because the laminate absorbed most of impact energy through formation of fiber cracks rather than delamination. Considering stacking sequence, the laminate GAG and GAA exhibited an energy threshold due to insensitivity to impact damage. As a result, the residual performance of composite was primarily dominated by delamination extent rather than fiber cracks.     

The comparison of low‐velocity impact resistance of aluminum/carbon and glass fiber metal laminates

This article presents the low‐velocity impact response of fiber metal laminates, based on aluminum with a polymer composite, reinforced with carbon and glass fibers. The influence of fiber orientations as well as analysis of load‐time history, damage area and damage depth in relation to different energy levels is presented and discussed. The obtained results made it possible to determine characteristic points, which may be responsible for particular stages of the laminate structure degradation process: local microcracks and delaminations, leading to a decrease in the stiffness of the laminate, as well as further damage represented by laminate cracks and its perforation. The damage mechanism of fiber metal laminates is rather complex. In case of carbon fiber laminates, a higher tendency to perforation was observed in comparison to laminates containing glass fibers. Delaminations in composite interlayers and at the metal/composite interface constitute a significant damage form of fiber metal laminates resulting from dynamic loads. Fiber metal laminates with glass fibers absorb energy mainly through plastic deformation as well as through delamination initiation and propagation, whereas laminates containing carbon fibers absorb energy for penetration and perforation of the laminate. POLYM. COMPOS. 37:1056–1063, 2016. © 2014 Society of Plastics Engineers     

Wasteless technology for production of fiberglass laminate based on aluminophosphate binder

Technology for production of glass laminate based on aluminophosphate binder involving pressure molding of previously dried glass fabric pieces with a deposited suspension of the powder filler in the binder (prepreg) allows for a considerable decrease in consumption of the initial components and significantly improves the mechanical strength of the material. The possibility of using crushed clippings and chips of glass laminate as a powder filler is demonstrated.     

Long-term behavior of partially cured epoxy prepreg systems under tensile loading

For the determination of the influence of processing conditions on the long-term behavior of high performance thermoset composites, two different glass fiber laminate systems with varying degrees of cure were examined. The laminates were conditioned in both moist and dry environments, and characterized via thermoanalytical and mechanical investigations. During the progression of moisture conditioning, both systems exhibited a reduction in the measured glass transition temperature as a result of the plasticization of the matrix. Tensile tests revealed that a direct correlation exists between the processing conditions and the long-term performance. Employing a linear model, the long-term mechanical behavior as a function of processing and moisture absorption can be described. Thus, the manufacturer has access to a tool for calculating the mechanical and thermomechanical properties depending on the processing and environmental conditions. Polym. Compos. 25:289–297, 2004. © 2004 Society of Plastics Engineers.     

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.     

Moisture absorption modeling using design of experiments

The effect of temperature and humidity on equilibrium moisture content of laminates was studied by response surface design. Two glass fabric‐reinforced laminated composite materials with different epoxy matrix resins, laminates A and B, were studied. Laminates A and B used are cyanate ester and polyphenylene oxide modified epoxy based laminate, respectively. The results show that the response surface profiles of moisture absorption for the two laminate materials are similar though their amounts of moisture absorption are different. The temperature‐humidity interaction effect and the quadratic effect of temperature are significant for laminate A. However, only the linear effects of temperature and humidity are significant for laminate B. Predictive models relating the important factors to the equilibrium moisture content were proposed in the article. The models developed can be used to predict and assess the reliability of the laminates for moisture related failures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1539–1543, 2007     

Bisphenol A dicyanate–novolac epoxy blend: Cure characteristics,physical and mechanical properties,and application in composites

Reactive blends of bisphenol A dicyanate (BACY) and a novolac epoxy resin (EPN) were investigated for their cure behavior and the mechanical, thermal, and physical properties of the cocured neat resin and glass‐laminate composites. Contrary to the apparent observation in DSC, the dynamic mechanical analysis confirmed a multistep cure reaction of the blend, in league with an established reaction path for similar systems. The cured matrix was found to contain both polycyanurate and oxazolidinone networks that existed in discrete phases exhibiting independent glass transitions in dynamic mechanical analysis (DMA). The flexible and less crosslinked oxazolidinone network contributed to enhanced flexural strength at the cost of the tensile strength of the neat resin. The increased resin flexibility was, however, not translated to the glass‐laminate composite for which the flexural strength decreased with the oxazolidinone content, although the latter was conducive for rendering a stronger interphase. The presence of oxazolidinone adversely affected the thermal stability of the cured resin and the high‐temperature performance of both neat resin and the composites. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1675–1685, 1999     

一种含尿素的苯并恶嗪的合成及其玻璃布层压板的研制

采用无溶剂法和有溶剂法分别合成了一种新型的苯并恶嗪预聚体,通过核磁共振氢谱、傅立叶红外光谱和差示扫描量热分析对苯并恶嗪预聚体的结构和固化行为进行了研究。并以苯并恶嗪预聚体为胶液、无碱玻璃布为基材,经浸胶、烘焙、压制制得一种玻璃布层压板。该层压板具有优良的力学性能、耐热性能、电绝缘性能、耐水及耐化学药品性能等。     

开环聚合酚醛树脂复合材料的研究──ALPF3-EGF层压板的研制

采用低分子量可溶性酚醛树脂合成了一种新型的苯并噁嗪中间体（ＡＬＰＦ３）树脂溶液,制备了高性能的玻璃布层压板。采用凝胶时间测定、差热分析和热重分析等方法研究了树脂的固化行为和热稳定性,确定了较为合理的玻璃布浸胶、烘焙和压制工艺,测试了玻璃布层压板的一般性能。结果表明,ＡＬＰＦ３树脂溶液及浸胶玻璃布贮存期长、工艺性好;玻璃布层压板性能优良,玻璃化转变温度达２８０℃,常态和１８０℃的弯曲强度为４６３ＭＰａ和３８０ＭＰａ,保留率达８２％。适用于１５５～１８０℃用的耐高温结构材料和电绝缘材料。     

The effect of fibre content on the thermal and fire performance of polypropylene–glass composites

Thermoplastic composites demand constant improvements in fire retardant and mechanical properties to fulfil their full market potential, especially in demanding sectors such as rail, aerospace and infrastructure, where fire performance is critical. The aim of this work is to understand the effect of reinforcing fibres on the flammability of polypropylene–glass (P‐G) composites and the means of improving their fire performance in a cost‐effective manner. A number of P‐G composites with 0%, 10% and 20% (w/w) glass fibres were prepared using short length glass fibres. The effect of fibre content on the thermal stability, flammability and mechanical performance of the P‐G composites without and in the presence of conventional fire retardants was studied. It was observed that while the presence of glass fibre lowered down the limiting oxygen index value of the composite, the rate of flame spread in a UL‐94 equivalent test was also lowered. The reduction in limiting oxygen index is due to the fact that glass fibre reduces the melt dripping behaviour of polypropylene and does not let the polymer (polypropylene) move away from flame, which then burns. Cone calorimetric study indicated that the presence of glass fibre reduces the overall flammability of the composite laminate. Copyright © 2011 John Wiley & Sons, Ltd.     

Numerical simulation study of ballistic performance of Al2O3/aramid-carbon hybrid FRP laminate composite structures subject to impact loading

Aramid-carbon hybrid fiber reinforced polymer (FRP) laminates have been widely used in the design of the ceramic/FRP laminate composite armor systems for their outstanding mechanical properties. In order to figure out the influence of the stacking sequence of the aramid-carbon hybrid FRP laminate on the ballistic performance of the ceramic/FRP laminate composite structures, a finite element model (FEM) which is used to simulate the condition of the 7.62 M61 AP against the Al₂O₃/aramid-carbon hybrid FRP laminate composite structure is carried out in ABAQUS/Explicit software, and the JH-2 constitutive model and 3D-Hashin failure criteria which is programmed by a user subroutine VUMAT are utilized to describe the mechanical behavior of Al₂O₃ and FRP laminate in this FEM. The accuracy of this FEM is checked by a verification FEM and the method of establishing this FEM is proved to be reasonable. The simulation results reveals that when the carbon fiber is stacked at the top of the aramid-carbon hybrid FRP laminate, the ballistic performance and the integrity of the geometry structure of the ceramic/FRP laminate composite structure is the best when the proportion of the carbon fiber in the hybrid FRP laminate is a constant, which provides an innovative way to enhance the ballistic performance of the ceramic/FRP laminate composite armor system.     

Processing of highly elastomeric toughened cyanate esters through a modified resin transfer molding technique

Model cyanate ester resins containing different quantities of epoxy functional butadiene-acrylonitrile rubber (ETBN) to improve the fracture performance were developed as matrices for composites. With the elastomeric modification, the resin systems exhibited rheological characteristics inappropriate for laminate fabrication by conventional resin transfer molding (RTM). To fabricate the carbon fiber based laminates in one liquid molding operation successfully, a process named bleed resin transfer molding (BRTM) was established. The BRTM process combines features of RTM and resin film infusion processes (RFI) and was therefore appropriate for processing high viscosity matrix resins. A novel catalyst was selected for the cyanate ester resin that provided enough latency for the impregnation steps in the BRTM process. Through the use of thermal analytical tools, a high degree of phase separation and conversion was obtained. The conversion and the glass transition temperature were found not to decrease with increasing elastomer content, which is in contradiction to most toughening modifications. Mode I and Mode II interlaminar fracture toughness were found to increase significantly with increasing elastomer content. In Mode I, an increase of up to 140% was observed. Collectively, this work showed that through the use of the BRTM technique, matrices with toughness improvements usually only achieved by prepreg systems can be processed in an RTM-like manner.     

Experimental failure analysis of bolted joints in moisture‐ and temperature‐induced composite laminates under preload

In this study, an experimental investigation was carried out in a bolted glass fiber‐reinforced laminate under preload moments. The stacking sequence at the composite laminate was chosen as [90°/0°/45°/−30°]_s. The preload moments were selected as 2, 4, and 6 Nm, in order to compare the influence of preload moments on failure modes and strengths. Some specimens were subjected to hot pure water at 70°C for 7 days. The bearing strength in this case was measured again under the same preload moments of 2, 4, and 6 Nm. It is found that the bearing strength of the specimen waited in hot water was 5.4% smaller than that of the specimen in dry condition. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Crack Suppression in Strongly Bonded Homogeneous/Heterogeneous Laminates: A Study on Glass/Glass-Ceramic Bilayers

A study is made of a glass/glass-ceramic bilayer as a model homogeneous/heterogeneous laminate. The underlying objective is microstructural design of ceramic layer systems with optimum mechanical properties, alternating hard layers, for wear resistance, with tough layers, for fracture resistance. Mica flakes in the glass-ceramic layer inhibit the propagation of well-developed intrusive cracks, by bridging; these same flakes render the structure susceptible to distributed damage, by providing discrete weakness at the microstructural level. A major distinguishing feature of the bilayer design is the incorporation of a strong interface, so that cracks are inhibited by the underlayer rather than deflected between the layers. Vickers and Hertzian indentation tests on specimen cross sections demonstrate the capacity of the glass-ceramic layer to arrest radial and cone cracks penetrating from the adjacent glass layer. Additional Hertzian tests on the outer surfaces of glass layers in a coating/substrate configuration show diffuse damage accumulation in the glass-ceramic substrate layers. This diffuse damage absorbs energy and shields cone cracks in the glass from the applied loading. Implications concerening the design of damage-tolerant laminate structures are discussed.     

玻璃纤维-铝合金层合板湿热老化性能研究

通过研究玻璃纤维-铝合金层板在70℃、RH85%湿热环境下不同老化周期后的力学性能、基体红外光谱、铝合金表面形貌及元素变化,分析了层板的湿热老化机理。结果表明:在加速湿热老化条件下,复合材料层内部基体会发生吸湿塑化,并破坏树脂与纤维以及铝合金层的界面,影响了材料内部应力的传递,使与界面及桥接应力相关的性能发生明显退化;表层铝合金层随湿热老化时间的延长,表面氧化加剧,使铝合金塑性降低,主要影响依靠铝合金承载的力学性能。     

Prediction of mechanical behavior of plastics undergoing decomposition from the combined effects of environmental exposure and stress

A study was made to determine whether the behavior of plastics undergoing breakdown from the effects of stress, elevated temperatures, and chemical attack could be predicted by means of a mechanical-chemical equation of state. Five systems were studied, the first four of which were tested for retention of strength at room temperature after environmental exposure: (a) glass-reinforced polyester laminate exposed to an alkaline medium at elevated temperatures; (b) cellulose laminate exposed to elevated temperatures, resulting in oxidative degradation; (c) paper-phenolic laminate exposed to elevated temperatures, resulting in further crosslinking followed by oxidative degradation; (d) heat-resistant glass fiber polyester resin laminate exposed to very high degradative temperatures; and (e) same material and treatment as (d) except that the specimens were under stress during the exposure (stress rupture). It is concluded that the effects of the various environments on the mechanical properties of the plastics under study can be predicted accurately by use of a parameter of the equation of state representing a second-order chemical reaction.