3D打印连续芳纶纤维增强聚乳酸复合材料的拉伸性能研究

将连续芳纶纤维(Kevlar)和聚乳酸(PLA)分别用作增强体和基体,同时引入熔融沉积成型(FDM)打印工艺制备样品,研究了打印层高、线宽、温度对连续芳纶纤维复合材料拉伸性能的影响。结果表明,随着打印层高与线宽的减小,试样中纤维含量逐渐增加,试样的拉伸强度显著增大。同时随着打印温度的增加,基体与纤维束结合加强,在一定范围内试样强度呈现上升趋势。当打印层高为0.3 mm,纤维体积分数为4.1%,试样的拉伸强度可达127 MPa,较纯PLA试样拉伸性能提高124.6%;较传统的纯PLA材料3D打印试样,连续芳纶纤维的加入极大地提高了试样的拉伸性能。     

波纹缺陷对复合材料层合板压缩力学性能影响研究

采用真空辅助灌注成型工艺与热压罐成型工艺,分别制备不同增强材料的标准压缩试样和含缺陷的压缩试样。压缩测试实验结果表明,压缩载荷下波纹缺陷引起压缩弹性模量和强度显著减小,并且对压缩强度的影响更加明显;同时,均一波纹对复合材料板材的压缩强度与压缩弹性模量的影响比梯度波纹更大;此外,波纹对碳纤维预浸料增强复合材料的力学性能影响更大,层间剪切破坏是试样主要失效机制,并且在纤维波纹的最大偏转角处,试样易发生横向剪切破坏。     

芳纶增强复合材料波纹夹层3D打印与力学性能研究

为解决波纹夹层结构传统制备方法存在的问题,采用熔融沉积(FDM)3D打印技术制备芳纶增强聚乳酸复合材料波纹夹层结构,并研究切片层高与打印温度对波纹夹层结构力学性能的影响。结果表明:当试样的切片层高为0.1 mm,打印温度为210℃时,复合材料波纹夹层结构的力学性能最好;试样的弯曲强度和冲击强度与切片层高呈负相关;随着打印温度的升高,试样的弯曲强度和冲击强度呈现先增大后减小的趋势。通过分析复合材料电镜图发现,切片层高的降低,有利于芳纶与聚乳酸基体的结合。     

成型工艺对玄武岩纤维增强PPS夹芯结构材料力学性能影响

夹芯结构材料具备质量轻、刚性高、功能综合型等优点,广泛应用于航天航空、交通运输、功能材料等领域。为研究成型工艺对夹芯结构材料性能的影响,以玄武岩纤维增强聚苯硫醚复合材料、连续玻璃纤维增强聚丙烯单向预浸带为原材料,探究了模压成型工艺中贴合压力、热压温度、热压时间以及芯层材料密度等因素对夹芯结构材料性能的影响。结果表明,模压成型工艺中热压温度和热压时间的最优条件为220℃,15 min;芯层材料的密度减小时,其弯曲性能、冲击强度呈先增大后下降的趋势,弯曲强度和弯曲弹性模量最大为271.53 MPa,18 672.72 MPa,冲击强度最大为119.21 kJ/m2。芯层材料的密度减小时,其弯曲刚度呈上升趋势,最大弯曲刚度可达15 441.16 N·mm。     

混杂纤维复合材料力学性能及其低速冲击性能研究

采用热压成型工艺制备单一碳纤维、碳纤维/玻璃纤维(CF/GF)和碳纤维/Kevlar纤维(CF/KF)均质和非均质混杂增强环氧树脂基复合材料,通过三点弯曲、层间剪切、低速冲击及冲后压缩性能测试,研究纤维组分、混杂结构和混杂比对复合材料力学性能及低速冲击性能的影响。结果表明,单一碳纤维复合材料力学性能最佳,其弯曲模量、弯曲强度和层间剪切强度分别达到66.16 GPa、830.35 MPa和42.73 MPa,而CF/GF混杂结构性能总体优于CF/KF混杂结构,内层混杂结构性能优于外层混杂结构;单一碳纤维复合材料低速冲击性能较差,其冲击损伤凹坑深度最高可达混杂结构的3.5倍,对应的分层阈值为2 723.53 N;CF/KF均质混杂结构的剩余压缩强度最大,而单一碳纤维复合材料则最小,对应数值分别为0.92和0.79。     

退火工艺对3D打印制品性能的影响

使用熔融沉积成型(FDM)工艺,3D打印了聚乳酸(PLA)和丙烯腈-丁二烯-苯乙烯塑料(ABS)材质的试样,并将试样在不同退火温度和时间下进行热处理。将退火后的试样进行拉伸性能测试、扫描电镜分析和X-射线衍射分析。结果表明:ABS试样在退火温度为40℃、退火时间为3 h时,平均拉伸强度和断裂伸长率最大。随着退火温度的提高,PLA试样的拉伸强度和结晶度均呈先增大后减小的趋势,且试样的拉伸强度和结晶度呈正相关关系。当退火温度为100℃、退火时间为1 h时,PLA试样的拉伸强度最大。通过扫描电镜观察发现,随着退火时间的延长,PLA和ABS打印试样的断面层间孔隙减小,丝材的粘结面积增大。     

中温固化环氧树脂芳纶Ⅲ纤维复合材料性能研究

对芳纶Ⅲ纤维和及其织物(F-3S175)的性能进行测试,采用热熔法制备了3233中温固化环氧树脂F-3S175芳纶布预浸料,通过热压罐法成型复合材料层合板和蜂窝夹层板,进行性能测试,与Kevlar 49纤维进行对比。结果表明,芳纶Ⅲ纤维、织物和其3233树脂复合材料性能高于Kevlar 49芳纶纤维、织物及其复合材料性能。     

格构腹板增强泡沫夹芯复合材料准静态压缩吸能试验

复合材料夹层结构具有轻质高强、弯曲刚度大、耐腐蚀、可设计性强、抗冲击、吸能效果好等特点,用玻璃纤维增强复合材料制作面板和格构腹板,以聚氨酯泡沫作为芯材,采用真空导入成型工艺,制备格构腹板增强泡沫夹芯复合材料试件。保持试件的平面尺寸不变,改变腹板间距、腹板高度、腹板铺层数和泡沫密度等参数,对试件进行准静态轴向压缩试验,对比研究其吸能性能。得到以下结论:格构腹板间距和厚度对抗压承载力和吸能性能影响较大,而泡沫芯材的密度影响较小;该新型复合材料的抗压承载力以及吸能性能随着腹板所占的体积比增大而增大,格构腹板对芯材的承载及吸能增强效果显著。     

3D打印参数对制品层间黏结性能的影响

研究了打印制品层间黏结性能与打印参数(如喷头温度、打印层高等)、退火与否以及打印材料种类之间的关系,使用桌面熔融沉积成型(FDM)成形机打印了一系列的标准拉伸及冲击性能测试样。结果表明,丙烯腈-丁二烯-苯乙烯共聚物(ABS)和聚乳酸(PLA)打印试样的拉伸强度和断裂伸长率均随着喷头温度的增加而提高,随层高的增加而下降;扫描电子显微照片表明,ABS和PLA试样均随着打印层高的增大,断面层间孔隙逐渐增大,丝材黏结面积减小;退火后,ABS试样的残余应力得到去除,拉伸强度和韧性得到稳定和改善,PLA试样蜷曲开裂现象加剧,拉伸强度和韧性下降。     

Nomex蜂窝夹层结构共固化技术及静态压缩力学性能研究

利用玻璃钢蒙皮和芳纶纸蜂窝,采用整体共固化的方式,对芳纶纸蜂窝夹层结构的一体化成型技术进行了研究,验证了蒙皮-蜂窝芯子-蒙皮(三明治结构)结构一体化成型的工艺可行性,并制备蜂窝夹层结构。通过比较夹层结构的粘接效果和面外静态稳定压缩测试,结合压缩应力-应变曲线,采用理论分析方法建立了夹层结构屈服强度本构方程。工艺试验和测试结果表明,采用玻璃钢蒙皮和芳纶纸蜂窝所制备的蜂窝夹层复合材料,蒙皮与蜂窝夹芯间胶接质量良好,弹性阶段面外静态稳定压缩强度达到5MPa,具备优异的层间和抗压性能,为其在相关领域的应用提供了一定理论基础。     

Fabrication process and mechanical properties of C/SiC corrugated core sandwich panel

Carbon fiber reinforced SiC composite is a kind of promising high-temperature thermal protection structural material owing to the excellent oxidative resistance and superior mechanical properties at high temperatures. In this work, a novel design and fabrication process of lightweight C/SiC corrugated core sandwich panel will be proposed. The compressive and three-point bending of the C/SiC corrugated sandwich panels are conducted by experiment and numerical simulation. The relative density of as-prepared C/SiC sandwich panel and the density composite material are 1.1 and 2.1 g/cm³, respectively. As the density of the C/SiC sandwich panel is only 52.3% of the bulk C/SiC, suggesting that lightweight characteristic is realized. Moreover, the C/SiC sandwich panel manifests itself as linear-elastic behavior before failure in compression and the strength is as high as 15.1 MPa. The failure mode is governed by the core shear failure and panel interlayer cracking. The load capacity under the three-point bending C/SiC composite sandwich panel is 1947.0 N. The main failure behavior is core shear failure. The stress distribution under the compression and three-point bend was simulated by FE analysis, and the results of numerical simulations are in accordance with the experimental results.     

固化压力对PMI泡沫/高温固化环氧碳纤维夹层复合材料胶接性能影响的研究

针对PMI泡沫/环氧碳纤维夹层结构复合材料的热压罐胶接成型工艺,系统研究了不同密度的PMI泡沫在0.2 MPa与0.3 MPa下的热稳定性能、蠕变性能。同时分别考察了不同厚度、不同处理条件的PMI泡沫在热压罐中的压缩变形情况,总结了压力对泡沫的尺寸稳定性的影响规律。通过研究PMI泡沫/环氧碳纤维夹层结构复合材料的力学性能,比较了不同固化压力下PMI泡沫与碳纤维面板胶接质量。结果表明,密度大的泡沫的抗蠕变性能好。泡沫的高温蠕变性能受压力影响敏感,随着压力增大,变形量迅速增大。经130℃热处理2 h后PMI泡沫的抗蠕变性有所提高。采用0.2 MPa与0.3 MPa胶接的PMI泡沫/高温固化环氧碳纤维阶层结构的抗滚筒剥离强度差别较大。抗剪切强度、抗平面拉伸强度及抗弯曲强度无明显差别。     

缝合增强泡沫夹芯结构复合材料力学性能研究

采用机械缝合设备连续制备了"X"型构型缝合增强泡沫夹芯结构预成型体,并采用真空导入模塑工艺(VIMP)整体成型了缝合增强泡沫夹芯结构复合材料。实验研究了面板纤维布层数、面板纤维布穿透缝合层数、缝合角度、缝合针距及纱线股数对缝合增强泡沫夹芯结构复合材料弯曲性能和平压性能的影响规律。实验结果表明:与未缝合结构相比,缝合结构在质量未明显增加的情况下,弯曲性能和压缩性能得到了显著提高,其弯曲刚度最大提高了4.66倍,破坏载荷最大提高了13.8倍;压缩强度和压缩模量最大分别提高了26.2倍和15.2倍。     

Dynamic viscoelasticity of hybrid kevlar and glass fiber reinforced LLDPE in the molten state

Kevlar and glass fibers were used to reinforce linear low density polyethylene (LLDPE), and composite sheets of 0.8, 1.5 and 2.5 mm thicknesses were obtained by using a compression molding technique. Dynamic viscoelastic properties of non‐hybrid and hybrid composites of various compositions at 200°C are evaluated. Storage modulus (G′) and loss modulus (G″) increase with angular frequency (ω) and reinforcement. Replacement of glass fiber by Kevlar at constant loading of fibers in LLDPE increases the value of G′, G″ and η′. The fractured surface of composite shows the gradient orientation of fibers particularly in 2.5 mm thick sheet. Top and bottom layers show relatively two‐dimensional orientation as compared to the middle layer, which shows random orientation. The orientation of fibers decreases G′ and η′ of Kevlar fiber and hybrid fiber hybrid fiber reinforced LLDPE composites. The effect of change in distance between parallel plate of rheometer (change in strain amplitude) on dynamic rheological properties is studied and reported here.     

Effect of borax on the thermal and mechanical properties of ethylene‐propylene‐diene terpolymer rubber‐based heat insulator

The effect of Borax on the mechanical and ablation properties of three different ethylene‐propylene‐diene terpolymer (EPDM) compounds containing 20 phr carbon fiber, 20 phr Kevlar or 10 phr/ 10 phr carbon fiber/ Kevlar was investigated. All formulations contained 30 phr fumed silica powder and 10 phr paraffinic oil. It was found that adding Borax to the composite samples containing carbon fiber or Kevlar fiber or their mixture with an equal ratio can increase the tensile strength, elastic modulus and hardness with a slightly decrease in the elongation at break of the rubber samples. The results of thermogravimetry analysis (TGA) on the various samples showed significant increase in the char yield at 670°C by adding Borax to the rubber compounds. Moreover, ablation resistance of samples was also improved by increasing Borax content. Meanwhile, density and thermal conductivity of the insulator were also reduced up to about 10% when the carbon fiber was replaced with the Borax. The results indicated that composites containing Kevlar have high storage modulus and produce compact and stable char. EPDM rubber composite containing Borax (20 phr), carbon fiber (10 phr), and Kevlar (10 phr) showed thermal and ablative properties comparable with those of the asbestos‐ filled EPDM. The thermal conductivity and ablation rate of the above‐ mentioned sample were 0.287 W/m/K and 0.13 mm/s respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41936.     

Nonwoven polylactic acid and flax biocomposites

Flax fiber‐reinforced polylactic acid (PLA) biocomposites were made using a new technique incorporating an air‐laying nonwoven process. Flax and PLA fibers were blended and converted to fiber webs in the air‐laying process. Composite prepregs were then made from the fiber webs. The prepregs were finally converted to composites by compression molding. The relationship between the main process variables and the properties of the biocomposite was investigated. It was found that with increasing flax content, the mechanical properties increased. The maximum tensile strength of 80.3 MPa, flexural strength of 138.5 MPa, tensile modulus of 9.9 GPa and flexural modulus of 7.9 GPa were achieved. As the molding temperature and molding time increased, the mechanical properties decreased. The thermal and morphological properties of the biocomposites were also studied. The appropriate processing parameters for the biocomposites were established for different fiber contents. POLYM. COMPOS., 34:1611–1619, 2013. © 2013 Society of Plastics Engineers     

Pultruded fiber reinforced thermoplastic poly(methyl methacrylate) composites. Part II: Mechanical and thermal properties

A novel process has been developed to manufacture poly(methyl methacrylate) (PMMA) pultruded parts. The mechanical and dynamic mechanical properties, environmental effects, postformability of pultruded composites and properties of various fiber (glass, carbon and Kevlar 49 aramid fiber) reinforced PMMA composites have been studied. Results show that the mechanical and thermal properties (i.e. tensile strength, flexural strength and modulus, impact strength and HDT) increase with fiber content. Kevlar fiber/PMMA composites possess the highest impact strength and HDT, while carbon fiber/PMMA composites show the highest tensile strength, tensile and flexural modulus, and glass fiber/PMMA composites show the highest flexural strength. Experimental tensile strengths of all composites except carbon fiber/PMMA composites follow the rule of mixtures. The deviation of carbon fiber/PMMA composite is due to the fiber breakage during processing. Pultruded glass fiber reinforced PMMA composites exhibit good weather resistance. They can be postformed by thermoforming, and mechanical properties can be improved by postforming. The dynamic shear storage modulus (G′) of pultruded glass fiber reinforced PMMA composites increased with decreasing pulling rate, and G′ was higher than that of pultruded Nylon 6 and polyester composites.     

Preparation and mechanical characterization of chicken feather/PLA composites

Green composites, a bio‐based polymer matrix is reinforced by natural fibers, are special class of bio‐composites. Interest about green composites is continuously growing because they are environment‐friendly. This study describes the preparation and mechanical characterization of green composites using polylactic acid (PLA) matrix including chicken feather fiber (CFF) as reinforcement. Extrusion and an injection molding process were used to prepare CFF/PLA composites at a controlled temperature range. CFF/PLA composites with fiber mass content of 2%, 5%, and 10% were manufactured. The effects of fiber concentration and fiber length on mechanical properties of CFF/PLA composites have been studied. Mechanical properties of composites were investigated by tensile, compression, bending, hardness, and Izod impact testing. The results of experiments indicated that Young's modulus, compressive strength, flexural modulus, and hardness of the PLA reinforced CFF composites are higher but tensile strength, elongation at break, bending strength and impact strength of them are lower than pure PLA. The results indicate that these types of composites can be used for various applications. POLYM. COMPOS., 38:837–845, 2017. © 2015 Society of Plastics Engineers     

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.