Manufacturing and mechanical characterization of perforated hybrid composites based on flexible polyurethane foam

This study focused on the fabrication and mechanical evaluation of nonwoven reinforced flexible polyurethane foam composites. Effects of perforation ratio, aperture size, and perforation depth on bursting and low‐velocity impact responses of perforated composite panels were investigated. The nonwoven fabric used for cover sheet was composed of flame retardant polyester, low‐melting point polyester, and recycled Kevlar staple fibers. Blending ratio of Kevlar fiber was confirmed to have relation to mechanical mechanism of cushioning layer. The highest mechanical strength value was obtained at 5 wt % of Kevlar ratio because of the highest cohesive force among recycled Kevlar, flame retardant polyester, and low‐melting point polyester fibers was provided at the blending ratio. The perforated high‐density flexible polyurethane foam composites panel was adhered with intra‐ply hybrid laminates with various areal densities on each face to form sandwich structural composites. The results revealed that perforation ratio and aperture significantly influenced the bursting and low‐velocity impact resistance behaviors of the perforated composites panel. Perforated composites with 10% perforation ratio and 4 mm aperture lead to maximum bursting strength of 437 N. Additional hybrid laminates significantly promoted the maximum bursting strength of the semiperforated hybrid composites by 212%. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42288.     

Intraply and interply hybrid composites based on E‐glass and poly(vinyl alcohol) woven fabrics: tensile and impact properties

E‐glass and poly(vinyl alcohol) (PVA) fibres were used to produce both homogeneous and hybrid composites with an orthophthalic unsatured polyester resin. Results are presented regarding the tensile and impact behaviour of both intraply and interply hybrid composites, with particular regard to the effects of the plies stacking sequence and the loading direction. With a proper choice of composition and stacking sequence, E‐glass/PVA hybrid composites were proved to achieve a property profile superior to those of homogeneous E‐glass laminates in terms of specific properties. In particular, hybridization with PVA fibres resulted in improving the specific impact energy of E‐glass laminates. Resistance to impact crack propagation was higher for intraply with respect to interply hybrid composites, as evidenced by their ductility index values. Copyright © 2004 Society of Chemical Industry     

三维正交机织玄武岩/芳纶混编复合材料的拉伸和剪切性能研究

本文设计和制作了两种混杂模式的三维正交机织玄武岩/芳纶混编复合材料,分别是层间混杂和层内混杂模式。对其拉伸性能和剪切性能进行了测试和分析,结果表明,层内混杂复合材料的拉伸性能和剪切性能比层间混杂复合材料的好,层内混杂复合材料的归一化强度和归一化模量分别比层间混杂复合材料的高22.12%和16.9%,层内混杂复合材料的剪切强度和剪切模量分别比层间混杂复合材料的高19.61%和26.03%;对于层间混杂复合材料,纬向的归一化强度比经向的高4.06%,但厚度方向上纱线的存在和织造工艺中经纱预加张力的影响,使纬向的归一化模量比经向的降低11.44%。     

Investigations on the performances of treated jute/Kenaf hybrid natural fiber reinforced epoxy composite

Natural fiber composite laminates are nowadays used in structural application such as aerospace, automobile and in sports goods because of their high strength to weight ratio and renewability. Hence the study of mechanical behaviors of natural fiber composites is very important in using these composite laminates for such specific applications. This project aims at identifying the mechanical properties of hybrid natural Jute/Kenaf fiber. The major drawbacks in natural fiber are its Resin incompatibility. Surface treatment of fiber is made to improve the interfacial bonding between the fiber and resin and to reduce the moisture absorption. Laminates are fabricated using Hand lay-up technique. Mechanical properties such as tensile, flexural, and Impact test for jute/kenaf hybrid laminates were obtained. Specimen preparation and Mechanical property testing were carried out as per ASTM standards. Micro structures of the different layer of hybrid specimens are scanned by the Scanning Electron Microscope.     

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.     

Hybridization effects on tensile and bending behavior of aramid/basalt fiber reinforced epoxy composites

In this study, the mechanical properties of aramid/basalt hybrid composite laminates were determined, and the effects of hybridization on the mechanical properties were investigated. To examine the effect of hybridization, the mechanical properties of aramid/basalt hybrid composite laminates were compared with those of aramid/epoxy and basalt/epoxy non‐hybrid composite laminates. The mechanical properties, tensile and flexural, of composite laminates were determined by performing uniaxial tensile and three‐point bending tests. The results showed that the employment of basalt fibers for partial substitution of aramid fibers in the composite laminate could provide improvements in the tensile and flexural properties. Furthermore, the results of three‐point bending tests were found that the employment of basalt fibers on compressive side across the thickness of composite laminates were realized significant improvement for flexural properties in comparison to the employment of basalt fibers on tensile side. POLYM. COMPOS., 38:1144–1150, 2017. © 2015 Society of Plastics Engineers     

聚氨酯软泡压陷性能的测试

介绍了软质聚氨酯泡沫塑料压陷性能的测试标准，不同厚度样品的压陷硬度测试值的差异，采用50%压缩负荷估计压陷硬度的简易测试方法，以及压陷性能测试的影响因素，并对测试聚氨酯软泡压陷性能的国家标准与国外标准的差别进行了比较。     

Comparison of foam core sandwich panel and through‐thickness polymer pin–reinforced foam core sandwich panel subject to indentation and flatwise compression loadings

Through‐thickness polymer pin–reinforced foam core sandwich (FCS) panels are new type of composite sandwich structure as the foam core of this structure was reinforced with cylindrical polymer pins, which also rigidly connect the face sheets. These sandwich panels are made of glass fiber–reinforced polyester face sheets and closed‐cell polyurethane foam core with cylindrical polymer pins produced during fabrication process. The indentation and compression behavior of these sandwich panels were compared with common traditional sandwich panel, and it has been found that by reinforcing the foam core with cylindrical polymer pins, the indentation strength, energy absorption, and compression strength of the sandwich panels were improved significantly. The effect of diameter of polymer pins on indentation and compression behavior of both sandwich panels was studied and results showed that the diameter of polymer pins had a large influence on the compression and indentation behavior of through‐thickness polymer pin–reinforced FCS panel, and the effect of adding polymer pins to FCS panel on indentation behavior is similar to the effect of increasing the thickness of face sheet. The effect of strain rate on indentation behavior of FCS panel and through‐thickness polymer pin–reinforced FCS panel were studied, and results showed that both types of composite sandwich panels are strain rate dependent structure as by increasing strain rate, the indentation properties and energy absorption properties of these structures are increased. POLYM. COMPOS., 37:612–619, 2016. © 2014 Society of Plastics Engineers     

制备工艺对亚麻增强聚丙烯复合材料拉伸性能的影响

以亚麻纤维为增强体,与聚丙烯（PP）长丝进行丝束级共混,形成PP包覆亚麻的纱线结构,利用机织工艺织成二维机织布,作为复合材料的预制件。采用层合热压方法制备PP／亚麻复合材料板材。通过对板材拉伸性能测试及扫描电镜（SEM）拉伸断口形貌分析,研究了不同纤维体积分数、织造密度及织造组织等因素对复合材料拉伸性能的影响。结果表明,在选取最优热压温度与压力的条件下,纤维体积分数为50％的板材性能最优;经向密度相同时,拉伸性能随着纬向密度的增加而提高;经、纬向密度均相同时,斜纹3／1组织的板材性能最优,纬向最大拉伸强度可达92．42 MPa。     

Investigations on physical,mechanical, morphological and water absorption properties of ramie/hemp/kevlar reinforced vinyl ester hybrid composites

Structural uses in the vehicle, aerospace, and sporting goods industries are being supplanted by hybrid composites that utilized natural fibers as reinforcements. The main focus of this work is to fabricate and characterize the ramie, hemp, and kevlar fabric reinforced hybrid vinyl ester composites. The composite laminates were fabricated via economically feasible and flexible hand lay-up technique. Overall six composites were prepared by varying the stacking sequence, including both hybrid and non-hybrid composites. The prepared composites were subjected to physical analysis (density, void fraction), mechanical tests (tensile, flexural, interlaminar shear, and impact test), morphological analysis (scanning electron microscopy), and water absorption test. The hybrid composites exhibited lesser void percentage than the non-hybrid composites. The mechanical properties were maximum for kevlar fabric skinned with core natural fabric reinforced composites (L-5, L-6) due to hybridization of highly strengthened kevlar fabrics. Moreover, the number fabric layers reinforced to achieve the standard thickness also affected the mechanical properties. All composite morphologies exhibited the same failure characteristics, including transverse interlaminar shear cracking, microbuckling, and fiber rip. The texture of the Kevlar yarns is uniform, but the texture of the natural fabric yarns is relatively less uniform. In comparison to the salt water medium, the percentage of water absorbed by composites in normal and distilled water was greater. This is due to the presence and accumulation of salt particles on the surface of the materials, which inhibits the action of water molecules, resulting in a drop in the proportion.     

硅橡胶泡沫/HGB复合材料的制备及性能

采用室温硫化法制备了一系列不同空心玻璃微珠（HGB）用量的硅橡胶泡沫（SF）/HGB复合材料,并研究了HGB用量对SF/HGB复合材料的交联密度、泡孔结构、机械性能、动态力学性能的影响。结果表明：HGB用量为6%时对应的SF/HGB6复合材料具有最佳的综合性能。通过静态压缩试验考察了SF/HGB6复合材料的缓冲性能,其缓冲系数与聚乙烯泡沫（EPE）非常接近。动态压缩疲劳试验结果表明,SF/HGB6复合材料具有较长的疲劳寿命（600万次）和较高的高度保持率（98.4%）,远高于EPE（29万次,54.5%）,并且SF/HGB6复合材料的缓冲系数在疲劳试验前后几乎没有变化,明显优于传统的缓冲材料EPE,可作为包装领域的缓冲材料。     

Mechanical, thermal and ablative properties of interply continuous/spun hybrid carbon composites

The mechanical and thermal properties of interply hybrid carbon fiber (continuous and spun fabric)/phenolic composite materials have been studied. Hybrid carbon/phenolic composites (hybrid CP) with continuous carbon fabric of high tensile, flexural strength and spun carbon fabric of better interlaminar shear strength and lower thermal conductivity are investigated in terms of mechanical properties as well as thermal properties.Through hybridization, tensile strength and modulus of spun type carbon fabric reinforced phenolic composites (spun CP) increased by approximately 28% and 20%, respectively. Hybrid CP also exhibits better interlaminar shear strength than continuous carbon fabric/phenolic composites (continuous CP).The in-plane thermal conductivity of hybrid CP is 4-8% lower than that of continuous CP. As continuous filament type carbon fiber volume fraction increases, the transversal thermal conductivity of hybrid CP decreases.The erosion rate and insulation index were examined using torch test. Spun CP has a higher insulation index than continuous CP and hybrid CP over the entire temperature range. Hybrid CP with higher content of spun fabric exhibits higher insulation index as well as lower erosion rate.     

Hybrid fiber fabric composites from poly ether ether ketone and glass fiber

Poly ether ether ketone (PEEK) polymer was extruded into filaments and cowoven into unidirectional hybrid fabric with glass as reinforcement fiber. The hybrid fabrics were then converted into laminates and their properties with special reference to crystallization behavior has been studied. The composite laminates have been evaluated for mechanical properties, such as tensile strength, interlaminar shear strength (ILSS), and flexural strength. The thermal behavior of the composite laminates were analyzed using differential scanning calorimeter, thermogravimetric analyzer, dynamic mechanical analyzer (DMA), and thermomechanical analyzer (TMA). The exposure of the fabricated composite laminates to high temperature (400 and 500°C) using radiant heat source resulted in an improvement in the crystallanity. The morphological behavior and PEEK resin distribution in the composite laminates were confirmed using scanning electron microscope (SEM) and nondestructive testing (NDT). Although DMA results showed a loss in modulus above glass transition temperature (T_g), a fair retention in properties was noticed up to 300°C. The ability of the composite laminates to undergo positive thermal expansion as confirmed through TMA suggests the potential application of glass–PEEK composites in aerospace sector. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117:1446–1459, 2010     

Hybrid effect on mechanical properties of M40‐T300 carbon fiber reinforced Bisphenol A Dicyanate ester composites

Interply and intraply hybrid composites based on Bisphenol A Dicyanate ester (BADCy), high strength carbon fibers T300, and high modulus carbon fibers M40 were prepared by monofilament dip‐winding and press molding technique. The tensile, flexural, interlaminar shear properties and SEM analysis of the hybrid composites with different fiber content and fiber arrangement were investigated. The results indicated that the mechanical properties of intraply hybrid composites were mainly determined by fiber volume contents. When the ratio of fiber volume content was close to 1:1, the intraply hybrid composites possessed lowest tensile and flexural strength. The mechanical properties of interply hybrid composite mainly depended on the fiber arrangement, instead of the fiber volume contents. The hybrid composites using T300 fiber layout as outside layer possessed high flexural strength and low flexural modulus, which was close to that of T300/BADCy composites. The hybrid composites ([(M40)_x/(T300)_y]_S) using M40 fiber layout as outside layer and T300 fibers in the mid‐plane had high flexural modulus and interlaminar shear strength. POLYM. COMPOS., 2010. © 2010 Society of Plastics Engineers     

Permanent indentation and damage creation of laminates with different composite systems: An experimental investigation

Quasi‐static indentation (QSI) and low‐velocity impact tests have been conducted to laminated composite specimens made from different composite systems. C‐scan and thermal deply techniques were used to observe the internal damage characteristics of the laminates. The test results show the effect of fibers and matrices on the permanent indentation and damage behaviors of composite laminates. Fiber breakage plays an important role in the formation of permanent indentation and the match between the fiber and matrix also has a significant influence on the permanent indentation and damage behaviors. A comparison shows the correlation between the peak load energy of the QSI tests and the knee point energy of the impact tests, based on which a condition for the prominent indentation formation was proposed for the impact tests. POLYM. COMPOS., 35:872–883, 2014. © 2013 Society of Plastics Engineers     

聚氨酯杂化复合泡沫体声学材料的研究

采用空心玻球、蛭石粉、粉末橡胶、有机蒙脱土和铅粉作为功能粒子,与聚氨酯杂化复合发泡,制得了聚氨酯杂化复合泡沫体声学材料。研究结果表明,加入20份上述不同功能粒子所制得的复合泡沫,它们之间的吸隔声性能差别不大,当厚度为25 mm时,在125~4000 Hz范围内的平均吸声系数在0.12~0.19之间,平均隔声量在12.0~13.9 dB之间,但它们的泡孔结构有较大的差别,其中,铅粉/PU复合体系的泡孔尺寸最粗,而有机蒙脱土/PU纳米复合体系的泡孔结构分布较均匀。所制得的几种复合泡沫都具有较高的拉伸强度,达到0.126 MPa以上,粉末橡胶/PU复合体系的泡沫拉伸强度达到0.406 MPa。     

准静态压痕作用下复合材料层合板损伤阻抗与损伤容限实验研究

参照标准实验方法,开展了复合材料层合板对准静态压痕力的损伤阻抗和损伤容限实验研究,获取了接触力、压痕深度、压头位移等实验数据,并对含静压痕损伤层合板进行了剩余压缩强度试验。研究了压痕深度-接触力与剩余压缩强度-压痕深度的变化关系,并讨论了准静态压痕过程中的损伤演变过程和层合板的压缩破坏模式。结果表明:当层合板表面出现目视勉强可见压痕时,初始损伤发生,压痕深度随接触力增大而明显增大,同时剩余压缩强度随压痕深度增加而明显降低;当达到最大接触力时,层合板失去承载能力,背面可看到大量纤维断裂。对于含静压痕损伤的层合板,压缩破坏模式为贯穿损伤区域的层合板断裂。     

Enhancement of fracture toughness of carbon fiber laminated composites using multi wall carbon nanotubes

In this paper, the effect of Multi Wall Carbon Nanotubes (MWNT) as a toughening agent of laminated composites is experimentally investigated. Carbon fiber laminates were manufactured by resin film infusion technique in which the resin flows in the through-the-thickness direction. The modified polymer systems showed 17% improvement in the stress intensity factor (K_Ic), whereas the laminated composites showed up to 48% improvement in Mode I and 143% improvement in Mode II fracture toughness. Scanning Electron Microscope (SEM) was then used to study the fractured surface and to explain the contrasting behavior of the MWNT-modified polymers when compared to the laminates.     

Effects of Thermal Aging on the Mechanical Properties of a Porous-Matrix Ceramic Composite

The present article focuses on changes in the mechanical properties of an all-oxide fiber-reinforced composite following long-term exposure (1000 h) at temperatures of 1000–1200°C in air. The composite of interest derives its damage tolerance from a highly porous matrix, precluding the need for an interphase at the fiber–matrix boundary. The key issue involves the stability of the porosity against densification and the associated implications for long-term durability of the composite at elevated temperatures. For this purpose, comparisons are made in the tensile properties and fracture characteristics of a 2D woven fiber composite both along the fiber direction and at 45° to the fiber axes before and after the aging treatments. Additionally, changes in the state of the matrix are probed through measurements of matrix hardness by Vickers indentation and through the determination of the matrix Young's modulus, using the measured composite moduli coupled with classical laminate theory. The study reveals that, despite evidence of some strengthening of the matrix and the fiber–matrix interfaces during aging, the key tensile properties in the 0°/90° orientation, including strength and failure strain, are unchanged. This strengthening is manifested to a more significant extent in the composite properties in the ±45° orientation, wherein the modulus and the tensile strength each exhibit a twofold increase after the 1200°C aging treatment. It also results in a change in the failure mechanism, from one involving predominantly matrix damage and interply delamination to one which is dominated by fiber fracture. Additionally, salient changes in the mechanical response beyond the maximum load suggest the existence of an optimum matrix strength at which the fracture energy in the ±45° orientation attains a maximum. The implications for long-term durability of this class of composite are discussed.     

混杂FRP复合材料单轴拉伸性能研究

为制备优异综合性能的混杂FRP(Fiber Reinforced Plastic/Polymer)复合材料,本文试验研究了芳纶、玄武岩、玻璃纤维与碳纤维混杂复合材料的单轴拉伸力学性能,分析了纤维种类、碳纤维相对体积含量、铺层方式等混杂参数对混杂效应的影响。结果表明,HFRP(Hybrid FRP)复合材料的单轴拉伸弹性模量基本符合混合定律,层间混杂FRP复合材料均表现出良好的混杂效应。当碳纤维铺层在中间时,碳/芳纶/玻璃层间混杂复合材料的混杂效应系数为0.647,混杂效应最优。