整体缝合夹芯结构复合材料压缩性能

设计了一种新型整体缝合夹芯结构。采用真空导入模塑工艺(VIMP)制备整体缝合夹芯结构复合材料, 研究其在平压载荷作用下的力学性能和破坏模式, 建立其有限元模型, 研究缝合纱线用量对整体缝合夹芯结构复合材料平压力学性能的影响。结果表明:该新型整体缝合夹芯结构复合材料能够在提高缝合纱线数量的同时避免一般斜缝方式引起纤维交叉损坏的弊端。整体缝合夹芯结构复合材料的压缩强度和压缩模量随着缝合纱线数量的增加而增大, 但缝合纱线含量较高时, 比压缩强度有所下降。数值计算结果与试验结果对比分析, 验证了所建立有限元模型的合理性, 说明该模型可用于预测其压缩模量。      

纤维缝合结构对夹芯结构复合材料力学性能的影响

通过RTM工艺成型了点阵增强夹芯结构复合材料,研究了纤维缝合结构对复合材料平压及侧压力学性能的影响,并探索了侧向压缩载荷下夹芯结构复合材料的破坏模式。结果表明,采用纤维缝合的方式可显著提高夹芯结构复合材料的力学性能。双向增强夹芯复合材料在长度和厚度方向上的侧压强度和模量相同,单向增强的侧压强度和模量表现出方向性,且长度方向上的模量明显高于宽度方向的。     

结构参数对树脂基纤维编织复合材料折叠夹芯结构力学性能的影响

折叠夹芯结构是一种新型的复合材料夹芯结构,其结构参数对力学性能有重要的影响。文中以碳纤维和Kevlar平纹编织预浸料为芯材原料,采用热压工艺,制备了复合材料折叠夹芯结构试样。通过压缩试验得到不同条件下折叠夹芯结构在静态压缩载荷作用下的力-位移变化曲线。构建了复合材料折叠夹芯结构有限元模型,对不同结构参数复合材料折叠夹芯的力学性能进行了数值模拟分析,并将模拟结果与实验结果进行对比验证了模型的可靠性。实验及数值模拟的分析结果表明,随着芯材厚度的增加,折叠夹芯层的压缩强度呈线性增加,其破坏形式由假塑性变形逐渐向脆性破坏转化;面板对夹芯层的约束作用能够极大地提高压缩模量和强度,而且上下面板对压缩性能曲线有着不同的影响;折叠夹芯单元的高度、长度、折叠夹角等参数对其力学性能具有不同程度的影响。     

陶瓷纤维增强氧化硅气凝胶复合材料力学性能试验

氧化硅气凝胶具有极低的热导率和密度,可作为很好的隔热材料,而脆弱的力学性能限制了其在隔热领域的应用。在不影响隔热效果的前提下,通过复合陶瓷纤维可增加氧化硅气凝胶的强度及韧性。试验探索了陶瓷纤维增强氧化硅气凝胶在室温下的拉伸、压缩和剪切等基本力学性能,分别研究了300℃、600℃和900℃下复合材料纤维铺层面方向的压缩性能,并采用扫描电子显微镜对高温试样微观结构进行了观察分析。结果表明：陶瓷纤维增强氧化硅气凝胶的性能表现出方向性,弹性模量在铺层面内方向与厚度方向的数值最大相差约28倍,强度极限亦然;在室温条件下,复合材料的拉伸和压缩弹性模量不同,X 、Y 和 Z 方向拉伸模量与对应的压缩模量之比分别为1.60、1.83和0.56;高温下复合材料沿厚度方向收缩,收缩量随温度升高而增大,900℃下的最大收缩量可达10.8%;高温下复合材料铺层面内方向压缩性能随温度升高而增强。     

缝合对泡沫夹芯复合材料低速冲击性能的影响EI北大核心CSCD

为了研究缝合对泡沫夹芯复合材料抗低速冲击的影响,以未缝合、全厚度缝合和冲击面纤维面板三类缝合碳纤维泡沫夹芯复合材料板为研究对象,采用落锤冲击试验机对泡沫夹芯复合材料板进行10J能量的冲击试验。然后使用水浸超声波扫描成像系统对冲击后的复合材料板进行损伤检测,得出泡沫夹芯复合材料板内部不同深度层的损伤情况。采用ABAQUS有限元软件对上述三类泡沫夹芯复合材料板进行有限元模拟,得出了低速冲击响应过程及面板的损伤情况,并进行了实验与数值模拟结果对比分析。研究结果表明,缝合会使得各铺层的损伤趋向均匀化,能够大幅提高层合板的整体性使各铺层之间的衔接更加紧密。在较小冲击能量下,全厚度缝合与冲击面纤维面板缝合都能够抑制分层的破坏,并且抑制分层的效果相差不大,且靠近冲击面的层与层之间更加容易产生分层的破坏。     

缝合对泡沫夹芯复合材料低速冲击性能的影响

为了研究缝合对泡沫夹芯复合材料抗低速冲击的影响,以未缝合、全厚度缝合和冲击面纤维面板三类缝合碳纤维泡沫夹芯复合材料板为研究对象,采用落锤冲击试验机对泡沫夹芯复合材料板进行10J能量的冲击试验。然后使用水浸超声波扫描成像系统对冲击后的复合材料板进行损伤检测,得出泡沫夹芯复合材料板内部不同深度层的损伤情况。采用ABAQUS有限元软件对上述三类泡沫夹芯复合材料板进行有限元模拟,得出了低速冲击响应过程及面板的损伤情况,并进行了实验与数值模拟结果对比分析。研究结果表明,缝合会使得各铺层的损伤趋向均匀化,能够大幅提高层合板的整体性使各铺层之间的衔接更加紧密。在较小冲击能量下,全厚度缝合与冲击面纤维面板缝合都能够抑制分层的破坏,并且抑制分层的效果相差不大,且靠近冲击面的层与层之间更加容易产生分层的破坏。     

共注射RTM成型一体化复合材料的热传导分析

依据已制备的碳环氧/泡沫/碳酚醛一体化复合材料结构,通过合理简化,建立了一体化复合材料结构热传导有限元模型.计算了指定热载荷条件下一体化复合材料结构内部温度分布,讨论了防热层厚度、隔热层厚度、隔热层热导率对一体化复合材料温度分布的影响.选用气凝胶复合材料为夹芯材料,计算得到了满足指定热载荷条件的隔热层的最小厚度,为以气凝胶复合材料为夹芯材料一体化复合材料热设计提供了依据.     

Z向点阵增强泡沫夹芯复合材料平压性能

设计了一种新型Z向点阵增强泡沫夹芯复合材料,以复合材料柱作为Z向点阵增强材料,并对不同分布密度Z向点阵增强材料的泡沫夹芯复合材料试验件进行了平压试验,探究了其平压力学性能和破坏方式。研究结果表明,当点阵间距为30 mm时,试样密度增加了2.8%,压缩强度和压缩模量分别提高了6.2倍和7.4倍。基于ABAQUS有限元软件建立了Z向点阵增强泡沫夹芯复合材料平压试验仿真模型,对其平压力学性能和破坏模式进行了模拟与分析。试验件平压强度有限元计算结果与试验结果偏差为10%左右,破坏方式与试验基本相同,验证了有限元模型的合理性和可靠性。     

碳纤维增强金字塔点阵夹芯结构的抗压缩性能

提出了一种碳纤维增强复合材料点阵夹芯结构的一体化成型工艺方法。该方法克服了传统夹芯结构面板与芯子之间因需要二次粘接或焊接的方法所带来弱界面的缺点。将纤维杆两端埋入面板内,使面板与芯子成为一体而不存在明显的界面。对用该方法制备的碳纤维增强金字塔点阵夹芯板进行平压试验,研究发现随着载荷的增加,纤维杆发生弹性屈曲并在中间部位出现断裂。理论分析了点阵夹芯结构平压载荷下的弹性模量和纤维杆极限屈曲载荷。通过与传统夹芯材料相比较发现,这种新型复合材料点阵夹芯结构具有密度低、比强度和比刚度高等优点。      

莫来石纤维增强SiO_2气凝胶复合材料的力学性能试验

为了探究莫来石纤维增强SiO_2气凝胶复合材料的拉伸和层间剪切性能,开展了相关试验。首先,进行了复合材料在室温下的面内拉伸试验,获得了复合材料的室温面内拉伸模量;然后,采用引伸计方法和数字图像相关法分别对拉伸变形进行测量,并对2种方法进行了对比分析;最后,开展了不同温度下的层间剪切试验,研究了复合材料在不同温度下的层间剪切性能,并对其微观结构进行了分析。结果表明:复合材料的拉伸模量约为285.17 MPa;由引伸计方法测得的拉伸变形计算出的拉伸模量比数字图像相关法获得的拉伸模量高2.4%;在室温和高温下,试样呈现明显的层间剪切破坏;对复合材料的微观分析发现,SiO_2气凝胶基体主要分布在层间区域,增强纤维主要分布在铺层内。所得结论表明莫来石纤维增强SiO_2气凝胶复合材料拉伸和层间性能较差,当承受层间载荷时,SiO_2气凝胶基体起主要作用,且温度对复合材料的性能影响较大。     

全厚度缝合复合材料泡沫芯夹层结构力学性能研究与损伤容限评定

探索了全厚度缝合复合材料闭孔泡沫芯夹层结构低成本制造的工艺可行性及其潜在的结构效益。选用3 种夹层结构形式, 即相同材料和工艺制造的未缝合泡沫芯夹层和缝合泡沫芯夹层结构及密度相近的Nomex 蜂窝夹层结构, 完成了密度测定、三点弯曲、平面拉伸和压缩、夹层剪切、结构侧压和损伤阻抗/ 损伤容限等7 项实验研究。结果表明, 泡沫芯夹层结构缝合后, 显著提高了弯曲强度/ 质量比、弯曲刚度/ 质量比、面外拉伸和压缩强度、剪切强度和模量、侧压强度和模量、冲击后压缩(CAI) 强度和破坏应变。这种新型结构形式承载能力强、结构效率高、制造维护成本低, 可以在飞机轻质机体结构设计中采用。      

Effects of thermal exposure on mechanical behavior of carbon fiber composite pyramidal truss core sandwich panel

An experimental study was performed to investigate the effect of high temperature exposure on mechanical properties of carbon fiber composite sandwich panel with pyramidal truss core. For this purpose, sandwich panels were exposed to different temperatures for different times. Then sandwich panels were tested under out-of-plane compression till failure after thermal exposure. Our results indicated that both the thermal exposure temperature and time were the important factors affecting the failure of sandwich panels. Severe reductions in residual compressive modulus and strength were observed when sandwich panels were exposed to 300 °C for 6 h. The effect of high temperature exposure on failure mode of sandwich panel was revealed as well. Delamination and low fiber to matrix adhesion caused by the degradation of the matrix properties were found for the specimens exposed to 300 °C. The modulus and strength of sandwich panels at different thermal exposure temperatures and times were predicted with proposed method and compared with measured results. Experimental results showed that the predicted values were close to experimental values.     

Compressive behavior of C/SiC composite sandwich structure with stitched lattice core

C/SiC composite sandwich structure with stitched lattice core was fabricated by a technique that involved polymer impregnation and interweaving. The mechanical behaviors of C/SiC composite sandwich structure were investigated at room temperature. The out-of-plane compressive strength was 20.97 MPa while modulus was 1473.55 MPa. The microstructural evolution on compression fracture surfaces of the stitching yarns was investigated by scanning electron microscopy, and the damage pattern of fibers on compression fracture surface was presented and discussed. Under an in-plane compression loading, the C/SiC composite sandwich structure displayed a linear-elastic behavior until failure. The peak strength and average modulus are 165.61 MPa and 19.74 GPa, respectively. The failure of the specimen was dominated by the fracture of the facesheet.     

Compression properties of fire-damaged polymer sandwich composites

The effect of fire-induced damage on the edgewise compression properties of polymer sandwich composites is investigated. Fire tests were performed using a cone calorimeter on sandwich composites with high or low flammability. The highly flammable composite had a poly(vinyl chloride) foam core, while the flame resistant composite had a phenolic foam core. The residual edgewise compression properties of the burnt composites were determined after fire testing at room temperature. The compression stiffness and strength of the two sandwich composites decreased rapidly with increasing heat flux and heating time of the fire due to thermal decomposition of the face skin and foam core. A large reduction to the edgewise compression properties of the phenolic-based sandwich composite occurred despite having good flame resistance, and the reasons for this are described. Preliminary analytical models are presented for estimating the edgewise compression failure load of fire-damaged sandwich composites that fail by core shear or buckling.     

Graded conventional-auxetic Kirigami sandwich structures: Flatwise compression and edgewise loading

The work describes the manufacturing and testing of graded conventional/auxetic honeycomb cores. The graded honeycombs are manufactured using Kevlar woven fabric/914 epoxy prepreg using Kirigami techniques, which consist in a combination of Origami and ply-cut processes. The cores are used to manufacture sandwich panels for flatwise compression and edgewise loading. The compressive modulus and compressive strength of stabilized (sandwich) honeycombs are found to be higher than those of bare honeycombs, and with density-averaged properties enhanced compared to other sandwich panels offered in the market place. The modulus and strength of graded sandwich panel under quasi-static edgewise loading vary with different failure mode mechanisms, and offer also improvements towards available panels from open literature. Edgewise impact loading shows a strong directionality of the mechanical response. When the indenter impacts the auxetic portion of the graded core, the strong localization of the damage due to the negative Poisson’s ratio effect contains significantly the maximum dynamic displacement of the sandwich panel.     

多级三角形格栅夹芯板力学分析

为了提高点阵复合材料结构的轻质高强力学特征,尤其提高其抗屈曲性能,设计了一种新型的多级三角形格栅夹芯板结构。根据等效连续介质力学方法提出了多级三角形格栅夹芯板的等效计算理论,预测了拉伸主导型多级三角形格栅夹芯板结构的等效弹性模量以及等效抗弯刚度。分析了侧压条件下多级三角形格栅夹芯板的弹性屈曲载荷和强度破坏模式。在理论模型的基础上绘制了侧压条件下多级三角形格栅夹芯板结构的失效模式图,指出了结构破坏模式与多级三角形格栅夹芯板尺寸之间的对应关系。研究表明:具有工字型截面的多级三角形格栅夹芯板结构相比于传统矩形截面格栅结构具有更高的抗弯刚度和弹性屈曲载荷,是一种性能更加优越的轻质高强点阵结构。      

The compressive responses of glass fiber composite pyramidal truss cores sandwich panel at different temperatures

A new method for fabricating glass fiber composite sandwich panel with pyramidal truss cores was developed based on the vacuum assisted resin transfer molding technology. The microstructure and organizations of fabricated sandwich panels were examined by the scanning electron microscope. The out-of-plane compressive tests of composite sandwich panels were performed throughout the temperature range from −60 °C to 125 °C. Then the effects of temperature on the compressive strength, compressive modulus and failure mechanism were investigated and analyzed. Our results indicated that cryogenic temperature resulted in the increasing of the compressive modulus and strength, while high temperature caused the degradation of the compressive modulus and strength. The effect of temperature on failure mode of composite sandwich panel was also observed. Analytical expressions were presented to predict the compressive modulus and strength of composite sandwich panels at different temperatures.     

缝纫泡沫夹层结构弯曲性能研究

本文对缝纫泡沫夹层复合材料进行了理论分析和三点弯曲实验研究.讨论了缝纫夹芯剪切模量的计算方法和计算公式.实验表明缝纫提高了泡沫夹层板三点弯曲破坏载荷.针对实验结果研究了材料性能和试件几何的关系,给出了缝纫泡沫夹层板破坏模式的判别公式并基于经典夹层梁理论建立了初始破坏载荷预估方法,预估值和实验值符合较好.