层间颗粒增韧HT3/QY8911的损伤阻抗和损伤容限

采用热塑性颗粒对双马基体复合材料层合板HT3/ Q Y8911 进行层间增韧, 制备未加入增韧颗粒的对比件和加入增韧颗粒的改性件。通过准静态压痕(QSI) 实验和冲击后压缩实验, 研究了层间增韧后HT3/ Q Y8911的损伤阻抗和损伤容限特性。结果和分析表明, 改性件在静压痕力下具有较高的分层起始载荷, 或在相同载荷水平下具有较小的损伤面积。提出从分层起始点载荷大小和载荷下降程度两方面来衡量试件对准静压痕力的响应。在相同的静压痕力或单位厚度冲击能量下, 层间增韧后的HT3/ Q Y8911 具有较深的凹坑, 表明塑性变形较大的层间区域以凹坑为代价换取了较小的损伤面积, 具有较高的损伤阻抗。在冲击后压缩面积相差不大的情况下, 层间增韧件的冲击后压缩强度和压缩破坏应变显著增加。      

“离位”增韧复合材料准静态压入损伤特性研究

采用"离位"增韧技术对双马来酰亚胺复合材料层压板进行了层间增韧,然后对增韧和未增韧的两种双马复合材料层压板进行准静态压入及冲击后压缩剩余强度试验研究,并用超声C扫描和热揭层对层压板的损伤进行测量。结果表明:经过"离位"增韧的双马复合材料层压板层间形成了热塑性树脂/热固性树脂双连续的结构,该结构不仅能抑制增韧层压板的内部损伤面积,改善损伤阻抗,使其表面凹坑深度更明显,而且还大幅提高了其损伤容限。     

低速冲击下层间增韧复合材料层压板损伤行为研究

为考察“离位”技术对双马来酰亚胺复合材料层压板层间增韧效果,对增韧程未增韧的两种双马复合材料层压板进行低速冲击性及冲击后压缩剩余强度实验研究.结果表明:经过“离位”增韧的双马复合材料层压板层间形成了热塑性树脂/热固性树脂双连续的结构,该结构不仅改善了材料的损伤阻抗,使其表面凹坑深度更明显,而且还大大提高了材料的损伤容限.     

层间韧化的碳纤维复合材料层压板的力学性能

研究了"离位"增韧的双马来酰亚胺复合材料层压板的Ⅰ型和Ⅱ型层间断裂韧性、层间微结构及其形貌变化、冲击分层损伤和冲击后压缩强度,以及典型面内、面外的基本力学性能.结果表明,通过热反应失稳分相、相反转和颗粒粗化等一系列过程,"离位"增韧在复合材料的层间形成了热塑性树脂/热固性树脂双连续的3-3相结构,这种结构大大提高了复合材料层压板的层间韧性、冲击损伤阻抗和损伤容限等性能.     

复合材料层压板抗冲击行为及表征方法的实验研究

对14种复合材料体系约800个试样进行了冲击阻抗和含损伤层压板压缩强度试验研究,研究发现对于同一种复合材料层压板的冲击能量-凹坑深度曲线和凹坑深度-压缩破坏应变曲线均存在拐点,在出现拐点后内部的分层损伤叠加面积基本不再增加,压缩剩余强度基本不再降低,表面冲击部位开始出现纤维断裂。研究表明,采用传统CAI来表征损伤容限性能的方法可能得到与实际结构损伤容限特性相反的结论。因此,提出了利用拐点附近特性来表征复合材料层压板的抗冲击行为（包括损伤阻抗和损伤容限）的建议,即分别采用QSI方法得到的准各向同性层压板的最大接触力F_max和压缩破坏强度（应变）的门槛值CAIT来表征复合材料层压板的损伤阻抗和损伤容限行为。      

热塑性颗粒-无机粒子协同增韧碳纤维增强环氧树脂复合材料

针对碳纤维增强环氧树脂(CF/EP)复合材料层间断裂韧性进行研究,通过在CF/EP复合材料层间添加四种无机纳米粒子和三种热塑性颗粒对其进行II型层间断裂韧性(G_IIC)研究,选择工艺性和增韧性效果好的两种无机纳米粒子和热塑性颗粒进行协同增韧研究。结果表明,CF/EP复合材料的G_IIC在适当的无机纳米粒子含量下都得到提高,这主要是由于无机纳米粒子在层间形成了有效吸收断裂能的微结构,纳米羟基氧化铝(AlOOH)的工艺性及增韧性等综合性能最好,AlOOH质量分数为1wt%时,CF/EP复合材料的G_IIC达到931 J/m2,提高了29.3%;热塑性颗粒中,改性聚芳醚酮颗粒(PAEK)的综合性能最好,添加10wt% PAEK,CF/EP复合材料的G_IIC可以提高32%,这是由于预制在层间的热塑性颗粒随着基体流动而得到扩散,形成了独特的跨层间连续结构,从而使裂纹扩展的阻力增加,有效提高了CF/EP复合材料的G_IIC;10wt%PAEK和1wt%AlOOH共同增韧CF/EP复合材料的G_IIC达到1 368 J/m2,相对于未增韧的CF/EP复合材料提高了90%,增韧效果比PAEK和AlOOH对CF/EP复合材料的增韧效果之和大,这表明,PAEK和AlOOH同时加入CF/EP复合材料层间,对CF/EP复合材料具有协同增韧效应。      

CFRP层合板抗分层损伤技术研究进展

碳纤维/聚合物基复合材料(CFRP)具有高比强度、高比模量、性能可设计、结构尺寸稳定性高、耐疲劳、耐腐蚀等优点而被广泛应用于陆、海、空、天等高性能载具中。各类碳纤维复合材料结构中,层合结构是主要结构形式。传统的CFRP层合结构中各铺层之间缺少纤维增强,故而导致CFRP层压板易产生层间分层且抗冲击损伤能力较低,因此层合板抗分层损伤和破坏方法成为关键问题和研究热点。本文综述了层合板抗分层损伤的方法,并对这些方法的适用性、优缺点进行了比较与阐述;重点归纳了利用碳纳米管提升层合板抗分层损伤的研究进展,并对碳纳米管的性能、增韧机理进行了阐述以及碳纳米管的增韧方法和效果进行了综述与归纳,讨论了"碳纳米管层间Z向增韧"进一步提高复合材料层间性能的可能性。     

炭纤维增强树脂基复合材料层合板低速冲击性能实验研究

对 3种炭纤维增强树脂基复合材料( T300/ N Y9200Z、T300/ Q Y8911和 T700S/ 5228)层合板进行了落锤冲击实验 , 并对冲击后试样进行了冲击后压缩性能测试。通过对凹坑深度2单位厚度冲击能量( d 2e)曲线 , 损伤面积2凹坑深度( S2d)曲线和冲击后压缩破坏应变2凹坑深度(ε 2d)曲线的对比分析 , 讨论了这 3 种复合材料层合板的低速冲击性能(即损伤阻抗和损伤容限) 。利用热揭层技术对拐点前后的复合材料损伤状态进行了观察 , 对损伤机制进行了讨论。实验结果表明 , 在 3种材料的 d 2e曲线 , S2d曲线和ε 2d曲线上均存在对应的拐点 , 该拐点同时也是不同损伤形式的转变点。凹坑深度在小于拐点时 , 损伤形式以基体裂纹和分层损伤为主 , 凹坑深度大于拐点时 , 分层损伤基本不再扩展 , 损伤的发展主要以纤维断裂的扩展为主。     

z-pin增韧复合材料层合板低速冲击损伤过程研究

从z-pin增韧复合材料层合板低速冲击实验出发,考虑了复合材料层合板在受低速冲击时的分层及基体开裂等四种损伤形式,引入适当的损伤判据,对T300/3234碳纤维树脂基复合材料层合板的低速冲击损伤过程进行有限元模拟。结果表明,采用碳纤维钉z-pin增韧使得冲击后层间分层区域面积减小50%左右,有限元结果与实验数据吻合。     

纤维增强热固性聚合物基复合材料层间增韧研究进展

综述了纤维增强热固性聚合物基复合材料（PMC）层间增韧的最新研究进展。热固性复合材料由于基体树脂高的交联密度而呈脆性,表现出低的冲击损伤阻抗和损伤容限特征。柔性聚合物层间增韧是改善聚合物基复合材料层间断裂韧性和抗冲击性的有效手段,且不会降低热固性树脂的热性能和高模量。目前有3种层间增韧方法：颗粒增韧、聚合物纤维增韧和薄膜增韧。讨论了3种方法的概念、实施方案、增韧机理及研究成果。最后重点阐述了创新性的复合材料“离位”增韧思想,介绍了具有全部自主知识产权的“离位”复合材料高性能化技术体系,包括预浸料和液态成型两大复合材料产品系列。     

ESTM-fabric/3266复合材料低速冲击响应及冲击后压缩行为研究

基于“离位”技术,分别开发两种新型聚醚砜(PES)点阵附载型(ES-L)和PES无规附载U3160织物型(ES-R)ES^TM-fabric织物,采用RTM工艺制备ES^TM-fabric织物增强3266中温环氧树脂基复合材料(ES^TM-fabric/3266),对其进行冲击阻抗及冲击后压缩测试,并利用荧光显微镜、SEM结果分析离位增韧机理,还对比研究未增韧U3160织物增强3266中温环氧树脂基复合材料的性能。低速冲击测试结果表明:相比未增韧U3160/3266(ES-U),ES^TM-fabric/3266的起始损伤阈值载荷显著提高,冲击损伤面积明显减少,裂纹扩展更加平缓,且以层内基体裂纹、纤维束内的纤维-基体脱粘和局部铺层断裂为主。ES-L的CAI值比ES-U增大了37%。ES-R层间出现均布式相反转结构,ES-L层间存在硬相区(富BMI连续相)和软相区(富PES连续相/3266相反转结构);ES-L的相结构能够更加有效地缓解应力集中、耗散冲击能量,从而使其表现出最佳的损伤阻抗和损伤容限性能。     

复合材料层合板静态压痕与损伤行为

发展了层合复合材料面内及分层失效模型,模型考虑了横向压剪残余剪切变形和分层残余相对位移。提出一种块体单元包含若干铺层的模型,以减少复合材料逐层分析时的计算量。对一种碳纤/环氧层合复合材料进行了横向压痕试验,测量了不同压力下凹坑的深度,用超声C扫测得损伤面积。用发展的模型在ABAQUS平台上通过用户材料子程序UMAT模拟了上述试验,分析了试验曲线特征点对应的损伤机制,通过与试验结果的对比,验证了本文模型的合理性。     

层状Ti3SiC2陶瓷的组织结构及力学性能

利用热压烧结TiH₂,Si和C粉获得了致密度大于98%的层状Ti₃SiC₂陶瓷。利用压痕法,在不同的载荷下测定了材料的维氏硬度, 发现其硬度值随载荷的增加而降低,在最大载荷30kg时,硬度值为4GPa。压痕对角线没有发现径向裂纹的出现。 这归因于多重能量吸收机制——颗粒的层裂、裂纹的扩展、颗粒的变形等。利用三点弯曲法和单边切口梁法测定了材料的强度和韧性分别为270MPa和6.8MPa·m1/2。Ti₃SiC₂材料的断口表现出明显的层状性质,大颗粒易于发生层裂和穿晶断裂,小颗粒易被拔出。当裂纹沿平行于Ti₃SiC₂基面的方向扩展造成颗粒的层裂,当裂纹沿垂直于基面的方向扩展时,裂纹穿过颗粒的同时,在颗粒内部发生偏转,使裂纹的扩展路径增加。裂纹的扩展路径类似人们根据仿生结构设计的层状复合材料。裂纹在颗粒内的多次偏转、裂纹钉扎以及颗粒的层裂和拔出等是材料韧性提高的主要原因。此外,在室温下得到的荷载-位移曲线,说明Ti₃SiC₂材料不象其它陶瓷材料的脆性断裂,而是具有金属一样的塑性。     

Mode I interfacial toughening through discontinuous interleaves for damage suppression and control

An investigation is described concerning the interaction of propagating interlaminar cracks with embedded strips of interleaved materials in E-glass fibre reinforced epoxy composites. The approach deploys interlayer strips of a thermoplastic film, thermoplastic particles, chopped fibres, glass/epoxy prepreg, thermoset adhesive film and thermoset adhesive particles ahead of the crack path on mid-plane of Double Cantilever Beam (DCB) specimens. During these mode I tests, the interlayers were observed to confer an apparent increase in the toughness of the host material. The crack arrest performance of individual inclusion types are discussed and the underlying mechanisms for energy absorption and the behaviour of the crack at the interaction point of the interleave edge were analysed using scanning electron microscopy.     

Dynamic delamination fracture toughness in unidirectional polymeric composites

A modified end-notched flexure (ENF) specimen was used to determine Mode-II-dominated dynamic delamination fracture toughness of fiber composites at high crack propagation speeds. A strip of FM-73 adhesive film was placed at the tip of the interlaminar crack created during laminate lay-up. This adhesive film with its greater toughness delayed the onset of crack extension and produced crack propagation at high speeds. Dynamic delamination experiments were performed on these ENF specimens made of unidirectional S2/8553 glass/epoxy and AS4/3501-6 carbon/epoxy composites. Crack speed was measured by means of conductive aluminum lines created by the vapor deposition technique. A finite-element numerical simulation based on the measured crack speed history was performed and the dynamic energy release rate calculated. The results showed that the dynamic fracture toughness is basically equal to the static fracture toughness and is not significantly affected by crack speeds up to 1100 m/s.     

Phase morphology of nanofibre interlayers: Critical factor for toughening carbon/epoxy composites

Electrospun thermoplastic nanofibres were employed to toughen carbon/epoxy composites by direct deposition on carbon fibre fabrics, prior to resin impregnation and curing. The toughening mechanism was investigated with respect to the critical role of phase morphology on the toughening effect in carbon/epoxy composites. The influences of solubility in epoxy and melting characteristics of thermoplastics were studied towards their effects on phase structure and delamination resistance. For the three different thermoplastic nanofibre interlayers used in this work, i.e. poly(ε-caprolactone) (PCL), poly(vinylidene fluoride) (PVDF) and polyacrylonitrile (PAN) nanofibre interlayers, only PCL nanofibres produced toughening. Although cylinder-shaped fibrous macrophases existed in all three interlayer regions, only PCL nanofibres had polymerisation-induced phase separation with epoxy, forming ductile thermoplastic-rich particulate microphases on the delamination plane. These findings clearly show that the polymerisation-induced phase separation is critical to the interlayer toughening by thermoplastic nanofibres. An optimal concentration (15 wt.%) of PCL solution for electrospinning was found to produce composites with enhanced mode I interlaminar fracture toughness (G_IC), stable crack growth and maintained flexural strength and modulus.     

玻璃纤维/环氧乙烯基酯树脂复合材料的层间增韧及其低温下低速冲击性能

采用真空辅助成型工艺(VARI)制备了四种无纺布(聚酰胺(PA)、聚氨酯弹性体橡胶(TPU)、乙烯-醋酸乙烯共聚物(EVA)、共聚酯(PEs))层间改性的玻璃纤维/环氧乙烯基酯树脂(GF/EVER)复合材料层合板.在温度为20℃下进行落锤冲击实验,对比分析了不同层间改性的GF/EVER复合材料层合板的低速冲击响应特性和...     

Acoustic Emission-Based Methodology to Evaluate Delamination Crack Growth Under Quasi-static and Fatigue Loading Conditions

The aim of this study was to investigate the applicability of acoustic emission (AE) technique to evaluate delamination crack in glass/epoxy composite laminates under quasi-static and fatigue loading. To this aim, double cantilever beam specimens were subjected to mode I quasi-static and fatigue loading conditions and the generated AE signals were recorded during the tests. By analyzing the mechanical and AE results, an analytical correlation between the AE energy with the released strain energy and the crack growth was established. It was found that there is a 3rd degree polynomial correlation between the crack growth and the cumulative AE energy. Using this correlation the delamination crack growth was predicted under both the static and fatigue loading conditions. The predicted crack growth values was were in a good agreement with the visually recorded data during the tests. The results indicated that the proposed AE-based method has good applicability to evaluate the delamination crack growth under quasi-static and fatigue loading conditions, especially when the crack is embedded within the structure and could not be seen visually.     

玻璃纤维/环氧树脂复合材料叠层板冲击损伤特性的若干实验研究

用落重法对玻璃纤维/环氧树脂[0₂/90₂/+45₂/-45₂]_s叠层板作低速冲击试验。检测复合材料内部损伤特性时,探索出一种价廉易得的元素造影液──乙酸锰/丙酮溶液代替昂贵的氯化金/乙醚溶液,可获得满意的效果。用热解剥层技术揭示了复合材料冲击损伤区的形貌特征,并研究了冲击能量与分层损伤实际面积之间的关系,发现起始层间开裂有一冲击能量门槛值,层间分层损伤面积与冲击能量呈线性关系。用扫描电镜观察冲击损伤区的微观形态,发现平行于纤维方向的开裂是基体受拉开裂、层间分层是剪切开裂。