不同缝合方式对缝合复合材料力学性能的影响研究

缝合技术作为整体成型的制造技术,能有效增强复合材料的层间强度和抗冲击损伤性能。在缝合技术中有不同的缝合方式,目前常用的缝合方式有锁式缝合、链式缝合和临缝三种。不同的缝合方式对复合材料的层间剪切性能、压缩性能、拉伸性能和弯曲性能会产生不同的影响。主要研究了在三种不同的缝合方式下,复合材料的压缩性能、拉伸性能和弯曲性能的变化。     

缝合泡沫夹层复合材料的滚筒剥离性能

制备了改进锁式缝合、临缝式缝合、双线链式缝合等三种缝合方式下不同缝合密度、缝线直径的缝合泡沫夹层复合材料,并对其滚筒剥离性能进行了测试。结果表明,未缝合泡沫夹层复合材料的剥离载荷上升到一定高度后便趋于稳定,而缝合泡沫夹层复合材料的剥离载荷上升到一定高度后呈正弦曲线变化;缝合后最大剥离载荷的平均值得到大幅度的提高,可增加到原有的1.6～4.7倍左右;缝合参数相同,缝合方式不同的缝合泡沫夹层复合材料的剥离载荷存在一定的差异,同样的缝合方式下,缝合密度、缝线直径越大,剥离载荷越大。     

缝合复合材料层合板的层间细观应力分析

介绍了缝合复合材料代表体单元（RVE）的三维细观有限元分析模型,模型考虑了缝线的实际形状以及缝合对层合板面内纤维的影响。在分析中引入了保证胞单元边界面的应力和位移周期性连续的边界条件。着重分析了三种平均应力状态下不同角度铺层间层间应力的分布情况。研究结果表明：缝合复合材料单胞内部层间应力分布也是不均匀的;促使材料发生分层破坏的主要层间应力和外载荷有关。     

缝合碳纤维泡沫夹芯复合材料低速冲击及损伤检测

研究了低速冲击对缝合与未缝合碳纤维泡沫夹芯复合材料冲击性能及损伤的影响;采用落锤冲击试验机对缝合和未缝合夹芯复合材料板分别进行了不同冲击能量下的冲击实验,得出冲击力和冲头位移分别随时间变化的曲线;采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,得出夹芯复合材料板内部损伤情况。结果表明,在相同冲击能量下,缝合碳纤维复合材料板的冲击力较未缝合的要大,但冲头接触时间要短;此外,缝合碳纤维泡沫夹层复合材料板比未缝合的损伤面积要小,这说明缝线能有效的抑制冲击载荷下复合材料板内损伤扩散,减小分层损伤面积,提高复合材料板的抗冲击性能;缝合的抑制损伤效果在表面层和最内部层效果显著,而在中间层缝线的效果一般。     

缝线捻度对链式缝合复合材料的浸润及力学性能影响

分别采用不同捻度的Kevlar-29缝线对碳纤维层合板预成型体进行链式缝合,并进行VARI(真空辅助树脂渗透)成型。研究了不同捻度缝合板的拉伸、弯曲及层间剪切性能和不同捻度缝线与树脂的界面结合情况。实验结果表明:缝合复合材料在缝线进行适当加捻之后,拉伸和弯曲强度都有不同程度提高,当捻度为80次/米时,分别较捻度为20次/米时提高了2.5%和9%,层间剪切强度降低了12%;且缝线捻度较低时,基本不会对树脂在缝线内部的浸润效果造成影响,捻度较高时,树脂渗透困难,对缝线浸润效果影响较大。     

缝合参数对缝合复合材料力学性能的影响研究

缝合复合材料因具有优异的抗冲击性能而在航空航天界得到广泛应用。在缝合时可以设置不同的缝合参数,主要包括缝合压力、针距和行距等。不同的缝合参数对复合材料制件的力学性能影响不同。本文主要研究了临缝和链式缝合两种缝合方式在不同的针距和行距缝合时,对缝合复合材料力学性能的影响,包括拉伸性能、压缩性能和剪切性能,从而来确定临缝和链式缝合的最佳缝合针距和行距。     

缝合技术在复合材料上的应用及研究进展

从缝合工艺特点及缝合参数等方面简述缝合技术,综述了近年来缝合复合材料的主要微观力学模型及缝合对复合材料力学性能的影响,介绍了缝合复合材料力学性能的研究进展,并对缝合复合材料的发展趋势进行了展望。     

碳毡复合材料无损检测对比试块设计及工艺

在飞机制造过程中需要进行大量超声波无损检测来检验复合材料制件内部质量.作为无损检测实施过程中对内部损伤评定的标尺,对比试块的需求量也应运而增.针对不同种类复合材料、不同结构零件,需要设计相应对比试块作为内部探伤依据.从材料特性及零件结构出发,根据穿透法A扫描可检测的缺陷类型,阐述带有不同角度碳毡的层状碳纤维复合材料结构...     

RTM注胶工艺对T形复合材料构件内部质量的影响

为提高树脂传递模塑(RTM)工艺成型T形复合材料制件的内部质量,研究了RTM成型T形复合材料制件工艺中3种注胶方式对内部质量的影响。无损检测结果表明,3种注胶方式对T形试样内部质量的影响不同。沿着T形制件横边两侧注胶,纵边出胶,成型的T形制件内部质量分布差异较大,存在明显的内部分层和密集空隙,存在内部缺陷的面积百分比近似20%;沿着T形制件横边一侧注胶,其余两边出胶,成型的T形制件只有个别位置存在密集空隙类缺陷,且缺陷所占百分比不足5%;沿着T形纵边注胶,横边两侧出胶,成型的T形制件内部质量完好。     

缝合参数对缝纫平纹玻璃纤维织物复合材料弯曲性能的影响研究

本文参照美国ACT计划设计的最优缝合参数,用无捻Kevlar纤维缝合成不同缝合密度的预成型体,讨论并优化了缝合过程中重要参数的影响。采用改良的缝合机器,使缝合质量大幅提升,并发展了加固嵌板的缝合技术。本文采用VARTM工艺制备玻璃纤维织物增强复合材料,通过比较不同缝合密度下的力学性能,讨论了VARTM工艺中缝合密度对材料性能的影响。实验结果表明,在一定的缝合密度下,缝合复合材料能表现出最好的冲击韧性。随着缝合密度的提高,复合材料的弯曲性能下降,但是层间性能有所提升。     

缝合对碳纤维复合材料性能影响研究

利用芳纶纤维对碳纤维增强环氧树脂复合材料进行缝合,研究了缝合密度、缝合方向和缝合线直径等缝合参数对复合材料拉伸性能、弯曲性能和层间剪切性能的影响。结果表明,缝合密度和缝合方向对材料性能影响较大,材料经缝合后拉伸性能和弯曲性能下降,层间剪切性能提高。     

Effects of stitch density and stitch thread thickness on mode II delamination properties of Vectran stitched composites

Abstract

Mode II delamination properties of Vectran stitched composites were investigated, and tabbed end notch flexural specimen testing was used to prevent premature failure. The effects of stitch density and stitch thread thickness were explored, and fibre compaction due to the stitching process was also verified. The results show that, in moderately stitched laminates (low stitch density), the improvement in G_IIC was negligible. Crack bridging by the stitch threads at the crack zone were mostly compensated for the effect of fibre compaction, which reduced the G_IIC values. Conversely, in densely stitched laminates (high stitch density), G_IIC values were improved significantly (2·4 times higher than those of unstitched laminates). The effects of stitch thread thickness appeared to be negligible in moderately stitched laminates. For densely stitched laminates, thicker stitch thread (500 denier) possessed G_IIC values that were 45·7% higher than thinner stitch thread (200 denier).     

捆绑纱对预定向经编织物性能的影响

通过用玻璃纤维／涤纶捆绑纱及不同经编组织结构,研究捆绑纱对预定向经编织物性能的影响。结果表明,玻纤可用于捆绑纱组织中,其编织后强度比涤纶纱高33．3％。玻纤捆绑纱可改善树脂对织物的浸渍性,降低最终复合材料的孔隙率,提高复合材料的拉伸和剪切等力学性能。不同的捆绑纱组织结构对复合材料的力学性能影响显著,玻纤做捆绑纱时,经平组织比编链组织复合材料的经向拉伸强度高7．97％,弯曲强度高约5％。     

A novel quartz fibre reinforced dense polyimide matrix composite: effect of preform stitching

ABSTRACT

A dense polyimide (PI) composite reinforced by quartz fibres (QFs), was prepared by vacuum assisted polymer infiltration and hot-pressing in this work. The microstructures and the mechanical properties of the as-fabricated composites were investigated. The results show a high flexural strength (≈686?MPa) of the composite, due to its dense nature. Moreover, there was no significant change in the bending strength of the stitched composites. The laminates mainly suffered delaminations and fracture of the QFs. The intralaminar bonding of the composite was enhanced by a novel stitching technique (all 28 layers stitched together by untwisted quartz filament tows in the plain stitch). As a result, the interlaminar fracture energy with 1 stitches?cm^?2 stitch density was increased by 87.1%, compared to that of the unstitched composite. In the case of stitched specimens, stitching plays an important role in improving the G_c and suppresses the influence of in-plane fibre orientation.     

Flow and void characterization of stitched structural composites using resin film infusion process (RFIP)

The resin film infusion process (RFIP), which is similar to resin transfer molding (RTM), was applied to investigate the possibility of manufacturing high performance stitched composites. With the objective of understanding the resin flow mechanisms and void formation in stitched fibrous perform, two recent technological developments in homogeneous tough resin and bendable stitching fibers were incorporated in producing stituched composites with RFIP. These included new lightly crosslinked thermosets (LXT) that were phenolic or amine based. Second, bendable carbon stitching reinforcement (T-900) was utilized as a stitching fiber. Flow characteristics were inferred by ultrasonic C-scan analysis of cured panels. Microscopic studies indicated that voids were distrubuted along the stitching fiber because of low consolidation pressure in the resin-rich area (stitching fiber region) where the fiber volume content was lower. In contrast to stitched composites, non-sitiched composites contained lower void content and irregular void distribution because of uniform fiber compaction. Microscopic studies of partially resin infused quasi-istropic stitched composites demonstrated that the resin flows along the stitching fiber region and then infuses into the fibrous preform. These infusion phebnomena were the result of anistropic permeability in the preform. Consequently, anisotropic resin flow in the stitched fibrous preform was found to be related to the heterogenous textile structure caused by the stitching process.     

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。