Effects of temperature on interlaminar fracture toughness of fibre reinforced plastic composites made by newly proposed rubber pressure moulding technique

Abstract

The present paper has investigated the effect of temperatures (i.e.?70–100°C) on the interlaminar fracture toughness (ILFT) of fibre reinforced plastic (FRP) composite panels made by a recently developed process known as the rubber pressure moulding (RPM) technique. The RPM technique is based on the matching die set, where the die is made of hard metal like steel and the punch from flexible rubber like materials. The use of flexible rubber punch helps to intensify and uniformly redistribute pressure (both operating pressure and developed hydrostatic pressure due to the flexible rubber punch) on the surface of the product. Natural rubber was used to prepare rubber punch in this investigation. For performance evaluation of FRP composites made by the RPM technique, FRP composites were also made by conventional method and tested at the same temperatures. It is observed that Mode I ILFT of FRP composites decreases towards higher and lower extremes of the temperature range selected. FRP composites made by the RPM technique show a higher Mode I ILFT over the 25–100°C temperature range than those made by the conventional process.     

Effect of rubber hardness on the properties of fiber reinforced plastic composites made by the newly proposed rubber pressure molding technique

The effect of rubber hardness on the properties of fiber‐reinforced plastic (FRP) composites is investigated in order to know the optimum composition of rubber mold used in rubber pressure molding (RPM) technique. A matching die set was used in RPM method, where the die was made of hard metal like steel and the punch from the flexible rubber like material, natural rubber. The use of flexible rubber punch generates and applies hydrostatic pressure on the surface of FRP composites. The hardness of rubber mold was controlled by incorporating carbon black as a filler material in the matrix of natural rubber and varied from 0 to 75 phr (per hundred rubber) in steps of 15 phr. Burn test, tension test, interlaminar shear test and interlaminar fracture toughness tests were conducted on the FRP composites to measure the void content, presence of delamination, tensile strength, inter laminar shear strength and inter laminar fracture toughness. The results are compared with the FRP composites made by conventional technique to evaluate the performance of RPM technique. It is observed that the laminates produced by RPM technique with different filler content in natural rubber mold show significant improvement in mechanical properties except interlaminar shear strength. POLYM. COMPOS., 28:618–630, 2007. © 2007 Society of Plastics Engineers     

Surface roughness of fiber reinforced plastic laminates fabricated using rubber pressure molding technique

The rubber pressure molding (RPM) technique for fabricating fiber reinforced plastic (FRP) laminates is a new development in manufacturing technology of FRP composites. The technique is based on the matching die set, where the die is made of hard metal like steel and the punch from the flexible rubber‐like material, natural rubber (NR). A split steel die and rubber punch are designed and fabricated to prepare the FRP product. The same split die is also used to cast the rubber punch. The use of flexible rubber punch applies hydrostatic pressure on the surface of the product. The rubber used to make the punch for pressing the component during curing process contains carbon black as filler material. The present study was carried out to investigate the effect of carbon black loading on the surface roughness of the FRP components produced by RPM technique. Natural rubber with different loading of carbon black (0 to 120 phr) was used for making the punch to fabricate the laminates through RPM technique. A number of FRP laminates with polyester resin and glass fiber were prepared to perform the experimentation. It was observed that as the loading of carbon black in rubber punch is increased from 0 to 120 phr, there is a significant decrease in the surface roughness of laminates. The surface roughness values of FRP laminates are correlated with a proposed model. POLYM. COMPOS. 27:504–512, 2006. © 2006 Society of Plastics Engineers     

Development of rubber pressure molding technique using butyl rubber to fabricate fiber reinforced plastic components based on glass fiber and epoxy resin

A rubber pressure molding (RPM) technique is developed to prepare fiber reinforced plastic components (FRP) using glass fiber and epoxy resin. The technique is based on the matching die set, where the die is made of hard metal like steel and the punch from flexible rubber like materials. The use of flexible rubber punch helps to intensify and uniformly redistribute pressure (both operating pressure and developed hydrostatic pressure due to the flexible rubber punch) on the surface of the product. A split steel die and rubber punch were designed and fabricated to prepare the FRP components. The same split die was also used to cast the rubber punch. Butyl rubber was used to prepare a rubber punch in this investigation. Burn test, coin test, scanning electron microscopy and mechanical tests like interlaminar fracture toughness, interlaminar shear test, tension test, etc were carried out to know the fiber content, void content, presence of delamination, bonding between fiber and resin, microstructure, and mechanical properties of the composite materials. These properties were also compared with FRP components made by the conventional technique to evaluate its performance in the structural applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1095–1102, 2006     

Pressure distribution analysis of fiber reinforced plastic components made by rubber pressure moulding technique

Fiber reinforced plastic component (FRP) having complex shaped geometry is prepared by rubber pressure molding (RPM) technique. The technique is based on the matching die set, where the die is made of hard metal like steel and the punch from flexible rubber like materials. The flexible rubber punch intensifies and uniformly redistributes pressure (both operating pressure and developed hydrostatic pressure due to the flexible rubber punch) over the surface of product. The distribution of pressure was analyzed by ANSYS over a processing pressure of 0.5–50 MPa. The analysis was extended to find out the optimum hardness of rubber mold, where the pressure distribution is uniform. For this, analysis was carried out for NR vulcanizates where the loading of carbon black was varied from 0 to 75 phr with an increment of 15 phr. The strain energy density function of 2‐, 3‐, 5‐ and 9 parameter Mooney‐Rivlin; 1st‐, 2nd‐, and 3rd order Ogden; Neo‐Hookean; 1st‐, 2nd‐, and 3rd order Polynomial; Arruda‐Boyce; 1st‐, 2nd‐, and 3rd order Yeoh; and Gent were used. 45phr carbon black loading NR vulcanizate shows best result. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Improving delamination resistance of carbon fiber reinforced polymeric composite by interface engineering using carbonaceous nanofillers through electrophoretic deposition: An assessment at different in-service temperatures

In this article, modification of carbon fiber surface by carbon based nanofillers (multi-walled carbon nanotubes [CNT], carbon nanofibers, and multi-layered graphene) has been achieved by electrophoretic deposition technique to improve its interfacial bonding with epoxy matrix, with a target to improve the mechanical performance of carbon fiber reinforced polymer composites. Flexural and short beam shear properties of the composites were studied at extreme temperature conditions; in-situ cryo, room and elevated temperature (−196, 30, and 120°C respectively). Laminate reinforced with CNT grafted carbon fibers exhibited highest delamination resistance with maximum improvement in flexural strength as well as in inter-laminar shear strength (ILSS) among all the carbon fiber reinforced epoxy (CE) composites at all in-situ temperatures. CNT modified CE composite showed increment of 9% in flexural strength and 17.43% in ILSS when compared to that of unmodified CE composite at room temperature (30°C). Thermomechanical properties were investigated using dynamic mechanical analysis. Fractography was also carried out to study different modes of failure of the composites.     

Stress relaxation behavior of glass fiber‐reinforced polyester composites prepared by the newly proposed rubber pressure molding

Stress‐relaxation behavior of glass fiber‐reinforced polyester composites, prepared by a recently developed manufacturing method called rubber pressure molding (RPM), is investigated with special reference to the effect of environmental temperature (−70°C to +100°C), fiber volume fraction (30–60%), and initial load level (1–5 kN). It is found that the stress‐relaxation rate decreases with an increase in the applied load of composites and a decrease in temperature. Below glass transition temperature, the rate of stress relaxation increases with an increase in volume fraction of fibers in the composites, whereas above glass transition temperature, it increases with a decrease in the volume fraction of fibers. The experimental results for a given composites are summarized by four values, the slopes of the two straight lines (two separate relaxation processes), and their intercepts upon the stress axis. Both the slopes are dependent upon the applied load, temperature, and volume fraction of fibers in the composites. Relaxation times in both primary and secondary are calculated over the wide range of temperatures, loads, and volume fraction of fibers in the composites. It depends strongly on the temperature, but does not depend strongly on the applied load and volume fraction of fibers. The performances of the composites are also evaluated through conventional compression‐molding process. The rate of stress relaxation is small when the composites are made of newly proposed RPM technique when compared with the conventional process. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Analysis of rubber pressure molding technique to fabricate fiber reinforced plastic components

A rubber pressure molding technique is developed to prepare fiber reinforced plastic components having complex shaped geometry. The technique is based on the matching die set, where the die is made of hard metal like steel and the punch from flexible rubber like materials. The use of flexible rubber punch helps to intensify and uniformly redistribute pressure (both operating pressure and developed hydrostatic pressure due to the flexible rubber punch) over the surface of product. The distribution of pressure was analyzed by ANSYS over a processing pressure of 0.5 to 50 MPa. The analysis was extended to find out the optimum hardness of rubber mold, where the pressure distribution is uniform. For this, analysis was carried out for NR vulcanizates where the loading of carbon black was varied from 0 to 75 phr, with an increment of 15 phr using the strain energy density function of two‐, three‐, five‐, and nine‐parameter Mooney–Rivlin, first‐, second‐, and third‐order Ogden, Neo–Hookean, first‐, second‐, and third‐order Polynomial, Arruda–Boyce, first‐, second‐, and third‐order Yeoh and Gent. 45 phr carbon black loading in NR vulcanizate shows best result. POLYM. COMPOS., 28:637–649, 2007. © 2007 Society of Plastics Engineers     

燃气流作用时间对玻璃钢层间剪切强度的影响

研究了不同燃气流作用时间对玻璃钢层间剪切强度的影响。研究结果表明:随着燃气流作用时间的延长,玻璃钢表面碳化失效层数呈增加趋势;未烧蚀部分复合材料层间剪切强度虽有降低,但是降低幅度不大,说明表面的玻璃布层碳化失效对深层复合材料层间剪切强度影响不大;烧蚀后复合材料断裂模式由韧性转变为脆性。该研究结果为玻璃钢在燃气流环境中的应用提供了重要的数据支撑。     

γ-射线辐照对聚丙烯腈纤维结构和强度的影响

采用γ-射线辐照方法对在氮气介质中的聚丙烯腈纤维进行处理,探索辐照剂量对纤维单丝拉伸强度和复合材料界面性能的影响。研究结果表明：在辐照剂量10-1000kGy范围内,随着辐照剂量的增加纤维单丝拉伸强度逐渐降低,同时辐照使得复合材料的层间剪切强度降低。进而采用原子力显微镜（AFM）对纤维表面形貌进行观察,用红外光谱（FT-IR）表征纤维表面化学结构,用X射线衍射（XRD）分析结晶状态,用差示扫描量热仪（DSC）测定纤维的耐热性能。     

不同种类拉挤FRP筋材压缩强度研究

针对拉挤纤维增强树脂基复合材料(FRP)筋材的压缩强度远低于其拉伸强度的问题,分别对玻璃纤维增强复合材料(GFRP)筋材、碳纤维增强复合材料(CFRP)筋材和混杂纤维增强复合材料(HFRP)筋材进行了端部有约束和无约束压缩实验,研究纤维类型、端部约束条件对FRP筋材在轴压状态下的破坏形式与压缩强度的影响规律。结果表明,无端部约束时不同纤维类型的FRP筋材的破坏现象与压缩强度差别较大;端部约束可以改变筋材的破坏方式,提高筋材的压缩强度;不同端部约束形式对不同FRP筋材压缩强度的提高作用不同。     

TDE-85/AG-80环氧树脂基复合材料微观形貌与力学性能分析

选用两种耐高温多官能团环氧树脂TDE-5和AG-80为基体,T300碳纤维为增强体制备了复合材料单向板,纤维体积含量均为60％。实验测得TDE-85树脂基体复合材料单向板的弯曲模量为74．26GPa,弯曲强度为1061．4MPa,层间剪切强度（ILSS）为54．05MPa;AG-80树脂基体复合材料单向板弯曲模量为55．73GPa,弯曲强度为840．52MPa,层间剪切强度（ILSS）为44．84MPa。前者的弯曲强度、弯曲模量与剪切强度也分别高出后者26．3％、33．2％与20．5％。实验对弯曲试样断口微观形貌的受压部分和受拉部分进行了SEM和高倍数码显微镜观察。结果显示,AG-80树脂基与碳纤维的界面结合情况较差,纤维成束被拔出,纤维表面几乎没有树脂。TDE-85树脂基与碳纤维界面结合情况较好,纤维与树脂结合比较紧密,断面较为平整,只有少量纤维拔出,表面粘附大量树脂。     

短纤维对橡胶发泡复合材料增强机理的细观分析

分别制备未增强的橡胶发泡体、未处理短纤维增强的橡胶发泡体和预处理短纤维增强的橡胶发泡体,考察气体泡孔和短纤维在橡胶发泡复合体中的微观形态,细观分析短纤维对橡胶发泡复合材料拉伸行为和压缩行为过程各阶段的增强机理。结果表明:气体泡孔在3种发泡复合材料基体中分布均匀,模压工艺使得短纤维在基体中呈现为平面分布,未处理短纤维周围有气泡包围,而预处理短纤维与橡胶间粘合良好;短纤维能有效地提高发泡复合材料在初始阶段的拉伸模量和100%定伸应力,特别是预处理短纤维表面与橡胶之间具有良好的粘合,有利于传递应力,限制橡胶基体的变形,而对拉伸强度却影响不大。在压缩弹性阶段,由于主要承载的泡壁中纤维呈平面取向,短纤维对压缩模量影响不大,但能有效地限制橡胶发泡复合材料在后屈曲阶段的压缩变形,提高其在高应变下的压缩强度,预处理短纤维增强效果明显高于未处理短纤维。     

Effects of novolac resin modification on mechanical properties of carbon fiber/epoxy composites

The epoxy resin matrix of carbon fiber (CF)‐reinforced epoxy composites was modified with novolac resin (NR) to improve the matrix‐dominated mechanical properties of composites. Flexural strength, interlaminar shear strength (ILSS), and impact strength were measured with unfilled, 7 wt% NR, 13 wt% NR, and 18 wt% NR filled to epoxy to identify the effect of adding NR on the mechanical properties of composites. The results showed that both interfacial and impact properties of composites were improved except for flexural property. The largest improvement in ILSS and impact strength were obtained with 13 wt% loading of NR. ILSS and impact strength were improved by 7.3% and 38.6%, respectively, compared with the composite without NR. The fracture and surface morphologies of the composite specimens were characterized by scanning electron microscopy. Intimate bonding of the fibers and the matrix was evident with the content of 7–13 wt% NR range. Decrease of crosslinking density and formation of NR transition layer were deduced with adding NR. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Diffusion of water and artificial seawater through coir fiber reinforced natural rubber composites

The diffusion of water and artificial seawater through cross‐linked coir fiber reinforced natural rubber composites was analyzed. The effect of fiber loading, chemical treatment, and bonding agent on liquid sorption was investigated. Based on the experiments, it is suggested that the probable mechanism of transport in gum compound is Fickian and that in composites is anomalous. The liquid uptake of all the composites is higher in water than that in artificial seawater. The composites showed increased swelling with fiber loading in water and artificial seawater. The influence of silica in the bonding system on swelling of the composites was also analyzed. In the case of gum compound, the desorption process is also Fickian, similar to the absorption of water and seawater. But the desorption of composites exhibited deviation from Fickian behavior. The effect of chemical treatment of coir fibers on the swelling was analyzed and found that the uptake of water and artificial seawater is reduced further in composites containing treated fibers. POLYM. COMPOS., 26:136–143, 2005. © 2005 Society of Plastics Engineers     

磷酸表面改性Kevlar纤维及其复合材料性能的研究

采用磷酸溶液对芳纶纤维(Kevlar)进行了表面改性,通过考察其表面化学结构、元素组成、表面形貌及表面粗糙度的变化研究了磷酸对Kevlar纤维表面改性的效果.结果发现,改性后的纤维表面引入了含氧基团,并产生了明显的刻蚀作用.利用溶液预浸渍工艺和高温模压成型技术制备了Kevlar增强双马来酰亚胺树脂(BMI)复合材料,通...     

高温老化对碳纤维增强双马来酰亚胺树脂基复合材料力学性能的影响研究

本文对国产碳纤维增强双马来酰亚胺树脂复合材料进行了高温老化力学性能测试和分析,通过扫描电子显微镜分析了高温老化对碳纤维／双马复合材料力学性能的影响。结果表明,老化1000h的力学性能未出现明显下降趋势,纤维与树脂基体粘接牢固,界面完好,该复合材料的高温老化性能优异。     

Effects of electrophoretic deposition process parameters on the mechanical properties of graphene carboxyl-grafted carbon fiber reinforced polymer composite

Carbon fiber (CF) modification by grafting of various graphene-based nanofillers (GBN) by electrophoretic deposition (EPD) technique was proven to be a successful technique to enhance the out-of-plane performance of carbon fiber reinforced polymer (CFRP) composites. Graphene carboxyl (G-COOH) grafting on carbon fiber by electrophoretic deposition (EPD) is a promising technique to improve the mechanical properties of CFRP composites. To our knowledge, there is a dearth of literature available on the effect of EPD process parameters on the mechanical behavior of modified CFRP composites. The aim of this study is to evaluate the effect of nanofiller concentration in the suspension, applied current, and the time of deposition during EPD on the mechanical behavior of nanophase CFRP composites, thus making it a novel work. With increasing concentration, interlaminar shear strength (ILSS) improved consistently and has shown a maximum enhancement of 24.7% than that of neat CFRP composite at 1.5 g/L nanofiller concentration, whereas flexural strength remained almost unaffected with varying concentration. On the contrary, variation of deposition current has affected the flexural strength but not ILSS. The maximum flexural strength was obtained at a deposition current of 5.0A with an improvement of 16.3% in comparison with neat CFRP samples. However, both flexural strength and ILSS of hybrid CFRP composites have shown improvement with increasing deposition time. At 60 min of deposition, ILSS and flexural strength have shown maximum improvements of 35.0 and 26.6%, respectively, when compared to control specimen. After evaluating the effect of process parameters future scope of the work involves the optimization of parameters for EPD of G-COOH. Fractographic analysis of the fractured samples was performed using scanning electron microscope (SEM) to apprehend prominent failure mechanisms. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48925.     

Comparative behavior under compression of concrete columns repaired by fiber reinforced polymer (FRP) jacketing and ultra high-performance fiber reinforced concrete (UHPFRC)

This paper summarizes the experimental results from a comprehensive research program to study the fundamental stress–strain behavior of damaged concrete repaired by two techniques: increased concrete section and bonding fiber reinforced polymer (FRP). In this work, two types of FRP composite jackets were used, carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer, and two types of concretes were used to repair the damaged concrete by increased concrete section: ordinary concrete and ultra high-performance fiber reinforced concrete (UHPFRC). Fifteen circular columns of concrete (110 × 220) cm³ were initially pre-damaged up to intense cracking, repaired by increased concrete section and by bonding FRP, and tested under uni-axial compression by loading up the damage. The impact of different design parameters, including plain concrete strength, types of composites, and type of concrete used for increasing section, was considered in this study. The strength enhancement and ductility improvement of specimens are discussed. A simple model is presented to predict the compressive strength of repaired damaged concrete columns. A significant strength and an increase in ductility were achieved, particularly when the columns were repaired by increasing section with UHPFRC and by bonding CFRP. These preliminary tests indicate that the use of UHPFRC is an effective technique for rehabilitating damaged concrete columns, highly competitive with the repaired concrete by wrapping specimens with FRP composite jackets.     

A simplified model for predicting the ignition of FRP composites with validation using intermediate‐scale fire experiment data

This study presents a simplified theoretical model to predict the ignition of FRP composites of general thermal thickness (GTT) subjected to one‐sided heating. A simplified GTT heat transfer model to predict the surface temperature of GTT composite panels was developed, and the exposed surface temperature was used as ignition criterion. To validate the GTT model, intermediate scale calorimeter fire tests of E‐glass fiber reinforced polyester composite panels at three heat flux levels were performed to obtain intermediate‐scale fire testing data in a controlled condition with well‐defined thermal boundary conditions. The GTT model was also verified by using results from finite element modeling predictions. This model can be used to estimate the surface temperature increase, time‐to‐ignition, and mass loss of FRP composites for fire safety design and analysis. Copyright © 2013 John Wiley & Sons, Ltd.