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     

基于温拌沥青技术的苯乙烯-丁二烯-苯乙烯嵌段共聚物/橡胶粉复合改性沥青应力吸收层层间性能

将3种不同的温拌剂添加到苯乙烯-丁二烯-苯乙烯嵌段共聚物（SBS）/橡胶粉复合改性沥青中,并拌和相应的应力吸收层混合料成型后制得复合式试件,通过黏度试验评价了不同温拌剂对SBS/橡胶粉复合改性沥青降黏效果的影响,通过层间拉拔试验、剪切试验和剪切疲劳试验分析了温拌SBS/橡胶粉复合改性沥青混合料应力吸收层层间性能的变化特性。结果表明,温拌剂的降黏效果由优到劣的顺序依次为:Evotherm-3 G、Sasobit-LM、Aspha-min,温拌沥青技术并不影响常温环境下复合改性沥青应力吸收层层间的黏结性能和抗剪性能;高温及水浴环境会导致不同应力吸收层层间力学强度明显降低,且不同温拌剂复合改性沥青应力吸收层的层间拉拔强度和抗剪强度存在差异,其中温拌剂Evotherm-3 G和Sasobit-LM能够增强应力吸收层层间的力学强度;相对于SBS/橡胶粉复合改性沥青的应力吸收层,添加温拌剂会缩短应力吸收层混合料的层间剪切疲劳寿命,Sasobit、Aspha-min和Evotherm-3 G温拌复合改性沥青应力吸收层的层间剪切疲劳寿命分别缩短了约10.0%、17.4%和2.7%。     

Effects of compaction and UV exposure on performance of acrylate/glass‐fiber composites cured layer by layer

With an aim to reducing manufacturing costs, in general and specifically to provide a solution to the thick laminate curing depth issue for composite materials, UV curing technology was combined with a fiber placement process to fabricate acrylate/glass‐fiber composites. A novel layer‐by‐layer UV in situ curing method was employed in this article and interlaminar shear strength (ILSS) tests and SEM were used to evaluate the effect of processing parameters, including compaction force and UV exposure dose, on ILSS. The SEM images from short‐beam strength test samples and the results of ILSS showed that the fibers' distribution was uniform in the cured matrix resin resulting from the compaction forces and that beneficially influenced the ILSS of the composite greatly. However, the matrix resin produced large shrinkage stresses when it reached a high degree of conversion (DC) in one‐step, which resulted in poor interlaminar adhesion. In addition, the fast curing speed of UV on the composite resulted in poor wetting between fiber and resin, and accordingly resulted in lower ILSS. To overcome these problems and obtain high ILSS value composites, an optimized compaction force and UV exposure dose were determined experimentally. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

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     

Characterization of Interlaminar Shear Strength of Ceramic Matrix Composites

The interlaminar shear strengths of three ceramic matrix composites have been characterized using a double-notch shear (DNS) test. The material systems investigated are plain woven C/SiC, plain woven SiC/SiC, and cross-plied SiC/calcium aluminosilicate-II. The use of the double-notch shear test for measuring the interlaminar shear strength of ceramic matrix composites is evaluated first. Numerical stress analyses are performed to investigate the effect of DNS specimen length, notch distance, and specimen supporting jig on the stress distribution in the expected fracture plane and the interlaminar shear strength. The numerical findings are then compared with an analytical model proposed elsewhere and correlated with the experimental results. The validity of this test technique has been established.     

Effect of quasi‐carbonization processing parameters on the mechanical properties of quasi‐carbon/phenolic composites

In this work, quasi‐carbon fabrics were produced by quasi‐carbonization processes conducted at and below 1200°C. Stabilized polyacrylonitrile (PAN) fabrics and quasi‐carbon fabrics were used as reinforcements of phenolic composites with a 50 wt %/50 wt % ratio of the fabric to the phenolic resin. The effect of the quasi‐carbonization process on the flexural properties, interfacial strength, and dynamic mechanical properties of quasi‐carbon/phenolic composites was investigated in terms of the flexural strength and modulus, interlaminar shear strength, and storage modulus. The results were also compared with those of a stabilized PAN fabric/phenolic composite. The flexural, interlaminar, and dynamic mechanical results were quite consistent with one another. On the basis of all the results, the quasi‐static and dynamic mechanical properties of quasi‐carbon/phenolic composites increased with the applied external tension and heat‐treatment temperature increasing and with the heating rate decreasing for the quasi‐carbonization process. This study shows that control of the processing parameters strongly influences not only the mechanical properties of quasi‐carbon/phenolic composites but also the interlaminar shear strength between the fibers and the matrix resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Experimental characterization of traditional composites manufactured by vacuum‐assisted resin‐transfer molding

The primary purpose of this study is to investigate the anisotropic behavior of different glass‐fabric‐reinforced polyester composites. Two commonly used types of traditional glass fabrics, woven roving fabric and chopped strand mat, have been used. Composite laminates have been manufactured by the vacuum infusion of polyester resin into the fabrics. The effects of geometric variables on the composite structural integrity and strength are illustrated. Hence, tensile and three‐point‐bending flexural tests have been conducted at different off‐axial angles (0, 45, and 90°) with respect to the longitudinal direction. In this study, an important practical problem with fibrous composites, the interlaminar shear strength as measured in short‐beam shear tests, is discussed. The most significant result deduced from this investigation is the strong correlation between the changes in the interlaminar shear strength values and fiber orientation angle in the case of woven fabric laminates. Extensive photographs of fractured tensile specimens resulting from a variety of uniaxial loading conditions are presented. Another aim of this work is to investigate the interaction between the glass fiber and polyester matrix. The experiments, in conjunction with scanning electron photomicrographs of fractured surfaces of composites, are interpreted in an attempt to explain the interaction between the glass fiber and polyester. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Experimental characterization of woven jute‐fabric‐reinforced isothalic polyester composites

In this article, mechanical performance of isothalic polyester‐based untreated woven jute‐fabric composites subjected to various types of loading has been experimentally investigated. The laminates were prepared by hand lay‐up technique in a mold. Specimens for tests were fabricated as per ASTM standards. All the tests (except impact) were conducted on closed loop servo hydraulic MTS 810 material test system using data acquisition software Test Works‐II. From the results obtained, it was found that the tensile strength and tensile modulus of jute‐fabric composite are 83.96% and 118.97% greater than the tensile strength and modulus of unreinforced resin, respectively. The results of other properties, such as flexural, in‐plane shear, interlaminar shear, impact, etc., also revealed that the isothalic‐polyester‐based jute‐fabric composite have good mechanical properties and can be a potential material for use in medium load‐bearing applications. The failure mechanism and fiber‐matrix adhesion were analyzed by scanning electron microscope. Effects of long‐term immersion in water on mechanical properties are also presented. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2650–2662, 2007     

Compressive behavior of biaxial spacer weft knitted fabric reinforced composite at various strain rates

The in‐plane and out‐of‐plane compressive properties of biaxial weft knitted E‐glass fabric reinforced vinyl ester composite at quasi‐static strain rate of 0.001/s and high strain rates from 700/s to 2200/s were tested to investigate the strain rate effect on the compressive behavior. The compressive tests were conducted on split Hopkinson pressure bar at high strain rate and on MTS 810.23 system at quasi‐static state. The experimental results indicated the strain rate sensitivity of compressive stiffness, failure stress, and strain of the composite in both out‐of‐plane and in‐plane compressive direction. The compressive stiffness and failure stress linearly increased with the increase of strain rate. The failure strain linearly decreased with the increase of strain rate. As the strain rate increased, the main failure mode at out‐of‐plane compression is the interlaminar shear failure and at in‐plane direction is the delamination. At the high strain rate of 2200/s, the composite coupon was compressed into debris with the shear or delamination failure. POLYM. COMPOS., 28:224–232, 2007. © 2007 Society of Plastics Engineers     

Delamination shape effects in aramid-epoxy-aluminum (ARALL) laminates with fatigue cracks

An aramid reinforced aluminum-epoxy-laminate, ARALL, which contains a fatigue crack and a delamination zone is analyzed. It is assumed that the interlaminar shear forces between the aluminum and aramid/epoxy layers are transmitted along the delamination boundary. The aramid/epoxy layer of the laminate is considered a series of linear springs. The tensile stress in the aramid/epoxy layer and the stress intensity factor in the aluminum layer are found for various experimentally observed delamination shapes. A residual strength criterion based on the maximum tensile stress in the aramid/epoxy layer is applied and the analytical results are correlated with the available experimental data.     

Improved part strength for the fused deposition 3D printing technique by chemical modification of polylactic acid

Fused deposition method (FDM) is popular as a plastic 3D printing technique. One of the drawbacks of this technology is its low bonding strength between layers, reducing through‐plane mechanical properties of a part compared with in‐plane strength within the layers themselves. This study focuses on altering the molecular structure of a polylactic acid by chain extension to increase the adhesion strength between layers, quantified by peel testing, in order to increase overall part strength. Four different samples were prepared in a high shear mixer, processed into filament and printed by a FDM‐type 3D printer. These samples were characterized for their thermal, rheological, mechanical and adhesion properties. The findings showed that the chain extender‐modified resins exhibited higher layer‐to‐layer adhesion strength as well as increased viscosity corresponding to an increasing degree of branching. The interlayer diffusion and entanglement of newly created branch chain ends improved bonding between the printed layers resulting in higher tensile properties. POLYM. ENG. SCI., 59:E59–E64, 2019. © 2018 Society of Plastics Engineers     

Characterization of interlaminar shear strength of laminated woven E‐glass/epoxy composites by four point bend shear test

An experimental and numerical investigation was performed to study the interlaminar shear response of laminated woven E‐glass/epoxy composites. The interlaminar shear strength results obtained from four point bend shear tests were compared with the results obtained from American Society for Testing and Materials (ASTM) test standards D2344 (short beam strength). The test results reveal that the four point bend interlaminar shear test results at a span to thickness ratio of 8 is higher than the short beam shear test results at a span to thickness ratio of 4. Numerical simulations were performed with ANSYS® software. The experimental results and the corresponding numerical results are in good agreement. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

风电叶片复合材料层间剪切破坏声发射监测

采用声发射技术对含分层缺陷风电叶片多轴向复合材料的层间剪切破坏实验进行实时监测,研究分层缺陷对复合材料层间力学性能的影响规律及其损伤破坏过程的声发射响应特征.结果表明,具有不同分层面积的两类复合材料试样破坏载荷相近,当分层缺陷位于剪切面中间位置时,分层缺陷大小对界面承载能力影响不大,损伤演化主要集中在剪切面上偏离中心两...     

The influence of various kinds of PA12 interlayer on the interlaminar toughness of carbon fiber‐reinforced epoxy composites

Modifying the impact toughness of carbon fiber‐reinforced epoxy composites by introducing thermoplastic inserts in the interlaminar layer is state‐of‐the‐art. This article compares the introduction of thermoplastics in continuous and discontinuous form. Test plate samples were produced using unidirectional noncrimp carbon fabrics with two different aircraft resin systems: HEXFLOW RTM6 (Hexcel) and Cycom 890 RTM (Cytec). In addition, Polyamide 12 (PA12) was laid in the interlaminar layer in the forms of two different laid scrims, as powder or as nonwoven fabric (NWF). The performance of the resulting combinations was assessed by testing the samples in Mode I and II interlaminar fracture toughness (GIc and GIIc), interlaminar shear strength (ILSS), and compression strength after impact (CAI). The results show that in nearly all the tests a fine‐mesh laid scrim performs similarly to a NWF with twice the weight per surface area. They show furthermore that the curing dynamics of the resin systems together with the melting characteristics of the thermoplastic during processing have an important effect on the performance of the test samples. Hardening of the resin before the PA12 reaches its melting point hinders the compacting of the thermoplastic. This limits the reduction in the original thickness of the insert, leading to an increase in the sample thickness and, thus, reducing the fiber volume content. Otherwise, the discrete arrangement of the laid scrim has positive effects on the material properties of the composite at elevated temperatures, considerably reducing the falloff in ILSS resulting from the temperature‐dependent Young's modulus of PA12. POLYM. COMPOS., 36:1249–1257, 2015. © 2014 Society of Plastics Engineers     

Interlaminar shear test by hybrid sandwich specimen under distributed load

A new method is proposed for the determination of the interlaminar shear strength of composites. The method is particularly pertinent to composites of high interlaminar shear strengths, where the ratio of tensile (compressive) strength to shear strength is relatively low. In such materials, including unidirectional composites with improved fiber/matrix bond strength and angle-ply laminates, an analysis based on a short beam interlaminar shear test is highly problematic and may, in fact, be erroneous. The test method is based on the use of a sandwich composite structure with a core made of layers of the tested composite and skins made of an elastic, strong unidirectional composite. A proper design procedure determines the choice of the skin material and of the relative thicknesses, so that flexural testing under distributed load leads to the intended core failure in shear. Calculations of the stress profile in a hybrid sandwich beam in bending and of the stress ratios under distributed load are presented. Also presented are experimental results recorded with sandwich hybrids made of unidirectional carbon-fiber-reinforced epoxy skins and a ±θ aramid-fiber-reinforced epoxy angle-ply core.     

Effects of quasi‐3D stacking architecture on interlaminar shear strength and void content of FRP

To improve the interlaminar shear strength (ILSS) of composite laminate, three different quasi‐3D stacking architecture (q‐3DSA) laminates were fabricated by using automated fiber placement process and a traditional 2D stacking architecture (2DSA) laminate was fabricated as the control sample. The distribution of voids, the density, and the ILSS of four types of laminates were tested. The results indicated that the void content of the different q‐3DSA laminates was approximately 0.71%–3.07% greater than that of the 2DSA laminate, but the ILSS of q‐3DSA laminates was 5.49%–12.54% better than that of the 2DSA laminate. The microstructure images showed that the cracks spread along the interface between the adjacent layers in the 2DSA laminate, while the cracks cross two or more layers in the q‐3DSA laminates. This behavior indicated that the q‐3DSA improved the ILSS by dispersing the interlaminar load through the bended and interlaced tows in the laminate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41076.     

Low‐cost,environmentally friendly route to produce glass fiber‐reinforced polymer composites with microfibrillated cellulose interphase

In this article, an easy, effective, and eco‐friendly method to improve the mechanical performance of glass fiber‐reinforced polymer composites is proposed, which involves the coating of unsized glass fiber fabric layers by simple immersion in an aqueous suspension containing sugarcane bagasse microfibrillated cellulose (MFC), followed by vacuum‐assisted liquid resin infusion as the processing method. From atomic force microscopy, a 250 nm MFC‐rich interphase was found, revealing its ability to build micro‐ and nanobridges acting as bulk epoxy matrix and GF linker. The interlaminar shear strength, quasi‐static tensile, and flexural tests, as well as the morphological and fractographic inspection of test coupons containing the secondary substructure, broadly supported the assumption of the efficient role on the interfacial level of this nano reinforcement by enhancing the load transference and distribution from the polymer matrix to the main reinforcing fiber system compared to baseline unsized fiber‐reinforced epoxy laminates. This finding permits this class of composite materials to be considered as having great potential to achieve products with excellent performance/cost ratios. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44183.     

Through Thickness Mechanical Properties of Chemical Vapor Infiltration and Nano‐Infiltration and Transient Eutectic‐Phase Processed SiC/SiC Composites

The through thickness (interlaminar) shear strength and trans‐thickness tensile strength of three different nuclear‐grade SiC/SiC composites were evaluated at room temperature by the double‐notched shear and diametral compression tests, respectively. With increasing densification of the interlaminar matrix region, a transition in failure locations from interlayer to intrafiber bundle was observed, along with significant increases in the value of the interlaminar shear strength. Under trans‐thickness tensile loading, cracks were found to propagate easily in the unidirectional composite. The 2D woven composite had a higher trans‐thickness tensile strength (38 MPa) because the failure mode involved debonding, fiber pull‐out and fiber failure.     

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.