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1.
三维编织C/SiC复合材料的拉压实验研究   总被引:10,自引:7,他引:10       下载免费PDF全文
针对三维编织C/SiC复合材料进行了拉伸试验和压缩试验,得到了材料拉伸、压缩的主要力学性能参数、损伤发展情况及破坏规律。从宏观角度比较了在两种载荷下材料弹性性能及强度的区别,得到了一些试验研究结论。结果表明:三维编织C/SiC在拉伸和压缩载荷下的应力-应变曲线有明显的非线性特性;拉伸模量低于压缩模量;拉伸强度高于压缩强度;声发射数据可以用来检测材料内部损伤的发展。  相似文献   

2.
本研究对三维针刺C/SiC(3-dimension needled C/SiC, 3D-N C/SiC)复合材料进行室温单调拉伸和拉伸加载-卸载试验, 利用声发射技术对试样损伤演化进行动态监测。采用K-均值聚类分析方法对小波降噪后的声发射信号进行了损伤模式识别, 结合试样断口扫描电镜观测, 发现3D-N C/SiC复合材料在拉伸载荷作用下主要存在五类损伤模式: 基体开裂、界面脱粘、界面滑移、纤维断裂和纤维束断裂。通过快速傅里叶变换(FFT)方法对小波降噪后的信号进行频谱分析得出: 3D-N C/SiC复合材料在拉伸载荷作用下主要存在240、370和455 kHz三种频率的损伤信号, 分别对应于界面损伤、基体损伤和纤维损伤。结合单调拉伸试验过程声发射信号能量柱分布和加卸载过程累积能量曲线特征, 分析了试样损伤演化机理。  相似文献   

3.
首先对复合材料单向板进行拉伸损伤实验,采用声发射监测其损伤的分布规律和发展过程,然后采用逐步线性加载的方式对三维有限元单胞模型进行应力场数值模拟,通过对应力场分布的分析获取复合材料的损伤机理,并进一步验证声发射监测的准确性.研究结果表明,通过综合运用声发射损伤监测技术与单胞模型有限元应力场数值模拟,分析复合材料拉伸损伤过程的方法是可行的.  相似文献   

4.
论述了声发射技术在三维编织复合材料弯曲过程中的应用及实验方法,给出了声发射在三维编织复合材料中弯曲过程的特征.为了精确地知道材料的损伤部位,声发射源信号的采集非常重要.试验结果表明,考虑到声发射源定位研究的准确性,建议采用波形分析法.在声发射信号的采集过程中比较了参数分析法和波形分析法.根据信号的衰减程度,选择较准确的声发射源信号.利用小波变换的不同算法得到了三维编织复合材料较准确的声发射信号.  相似文献   

5.
风电叶片复合材料拉伸损伤破坏声发射行为   总被引:2,自引:0,他引:2  
通过风电叶片单向和多向复合材料拉伸力学性能实验, 结合声发射技术, 研究复合材料损伤演化特性及纤维预断缺陷对复合材料力学性能的影响。复合材料单向和加卸载拉伸实验时, 采用声发射实时监测整个损伤破坏过程, 获取复合材料试件的拉伸力学性能、 损伤破坏特征及相应的声发射响应特征。结果表明: 由于纤维预断缺陷的存在, 单向复合材料加载到约30%破坏载荷时, 缺陷位置及相邻区域的基体和界面开始出现明显损伤; 加载到约60%破坏载荷时, 含缺陷层和相邻的层出现明显的层间剪切破坏, 导致刚度的急剧缩减, 声发射撞击累积数明显高于无缺陷试件。含纤维预断多向复合材料加载到约60%破坏载荷时, 纤维预断处树脂基体出现明显损伤; 随相对应力水平的提高, 多向复合材料的Felicity比下降较为平缓。  相似文献   

6.
风电叶片复合材料拉伸损伤破坏声发射行为   总被引:1,自引:0,他引:1  
通过风电叶片单向和多向复合材料拉伸力学性能实验,结合声发射技术,研究复合材料损伤演化特性及纤维预断缺陷对复合材料力学性能的影响.复合材料单向和加卸载拉伸实验时,采用声发射实时监测整个损伤破坏过程,获取复合材料试件的拉伸力学性能、损伤破坏特征及相应的声发射响应特征.结果表明:由于纤维预断缺陷的存在,单向复合材料加载到约30%破坏载荷时,缺陷位置及相邻区域的基体和界面开始出现明显损伤;加载到约60%破坏载荷时,含缺陷层和相邻的层出现明显的层间剪切破坏,导致刚度的急剧缩减,声发射撞击累积数明显高于无缺陷试件.含纤维预断多向复合材料加载到约60%破坏载荷时,纤维预断处树脂基体出现明显损伤;随相对应力水平的提高,多向复合材料的Felicity比下降较为平缓.  相似文献   

7.
三维编织碳/环氧复合材料力学性能测试及破坏机制   总被引:1,自引:0,他引:1       下载免费PDF全文
通过宏观拉压试验, 研究了三维正交编织碳/环氧复合材料的拉伸和压缩力学性能。对试验过程进行了声发射分析, 对断口进行了扫描电镜观察分析, 给出了该类材料的拉伸和压缩破坏机制。结果表明: 三维正交编织碳/环氧复合材料有良好的拉伸和压缩力学性能; 三维正交编织复合材料在拉伸和压缩载荷作用下的断裂均为脆性断裂, 拉伸试验的主要破坏现象是纤维断裂拔出, 而压缩试验则是纤维剪切破坏; 通过声发射参数分析可以基本判定该类材料损伤过程中的损伤类型。  相似文献   

8.
采用声发射平均频率和相对能量以及幅值识别了3D C/SiC复合材料的拉伸损伤模式,探讨了拉伸加卸载过程中材料的费利西蒂(Felicity)效应。通过分析具有不同拉伸性能试样的损伤过程,研究了不同损伤模式的时间分布特征对材料拉伸性能的影响关系。分析结果表明,3D C/SiC复合材料中基本不存在凯瑟(Kaiser)效应,Felicity比随着应力水平的升高而降低,相对应力水平高于65%时出现突降。3D C/SiC复合材料高性能的决定性因素不是声发射波击总数,而是高幅高能量信号发生的时间和次数。在加载前期(应变0.15%)损伤较少是材料高强度的必要条件,纤维簇断裂在加载中后期的分散分布有利于提高拉伸强度。  相似文献   

9.
对密度为1.65 g/cm3、1.75 g/cm3和1.85 g/cm3的平纹编织C/SiC复合材料进行单向拉伸试验,获得材料的基本力学性能。采用声发射技术对材料在单调拉伸试验全程下的损伤信号进行监测,并对采用Wavelet小波方法降噪后的声发射信号进行特征参数分析和K-聚类分析。结合SEM图像分析发现材料密度的不同使材料损伤模式、损伤演化过程及破坏模式存在差异。根据损伤模式和声发射事件分布特征将试验声发射信号进行分类分析,研究不同密度材料的损伤模式和损伤演化机制,发现:随着密度增大,不同损伤模式发生的起始应力水平、相对时间及频数逐渐增大。分析得出结论:材料密度通过影响基体损伤程度和损伤分布区域以及界面性能改变材料力学性能。  相似文献   

10.
在对C/SiC复合材料常温拉伸试验的损伤表征和声发射演化特性进行简要分析的基础上,针对构件集成式设计带来的复杂性特点,对某C/SiC热结构在常温静力试验中的声发射特性进行了分析。给出了试验中声发射特征参数的分类特点。根据试验加载中声发射信号规律,给出了结构的损伤演化模式。通过与材料级声发射信号的对比,判断了试验加载与热结构极限破坏载荷之间的裕度。由此将声发射测试从材料级别的研究延伸到大型C/SiC热结构。  相似文献   

11.
多龄期桥梁斜拉索疲劳损伤演化声发射监测技术研究   总被引:3,自引:1,他引:2  
斜拉索在斜拉桥体系中有着举足轻重的作用,但易遭受腐蚀和疲劳累积损伤。目前对多龄期斜拉索腐蚀疲劳损伤演化规律的研究还较少。拟采用声发射技术监测国内某大桥腐蚀斜拉索疲劳损伤演化过程。首先,通过拉伸试验,得到了斜拉索中腐蚀钢丝和未腐蚀钢丝的应力-应变关系曲线,其实验结果表明腐蚀对斜拉索力学性能有较大的影响;其次对大桥拆下来的多龄期斜拉索进行疲劳测试,运用声发射技术监测了它的动态损伤过程,获得了斜拉索整个损伤过程的声发射特征参数,根据声发射累积能量参数分析结果,得到了多龄期斜拉索疲劳损伤演化规律;最后,对斜拉索疲劳损伤演化的各个阶段声发射波形进行小波分析,提取出各自的特征波形,并运用FFT分析其频率分布范围,进一步分析了损伤的形成原因,实现了对多龄期斜拉索损伤声发射源类型的确定  相似文献   

12.
采用声发射技术对不同几何尺寸的碳纤维增强环氧树脂复合材料(CFRP)螺栓连接结构在静力载荷下破坏行为进行了试验研究,比较了不同几何构型下的连接结构的破坏行为与声发射信号之间的映射关系。采用声发射技术对结构损伤过程中的声发射信号进行全程采集与转换,结合CFRP螺栓结构的载荷-位移曲线和宏/细观破坏形貌,分析了幅值、熵曲线和Andrews曲线与破坏行为之间的关系。结果表明:挤压与剪切破坏试件的载荷-位移曲线均呈现出较明显的塑性特征。结构发生挤压和剪切破坏时,声发射信号以中幅值信号为主,并伴随少量高幅值信号;结构发生拉伸破坏时对应的幅值为中幅值信号。根据熵曲线特征将CFRP连接结构破坏过程分为四个阶段,在损伤演化阶段发生纤维断裂、分层等失效模式,在结构失效阶段以分层失效为主。基于Andrews曲线分析得到挤压和拉伸失效模式在损伤演化阶段会出现多种损伤类型,剪切失效模式在结构失效阶段会出现多种损伤类型。  相似文献   

13.
Large Scale Bridging in SiC/MAS-L (ceramic glass matrix) composites was investigated by using DEN specimens under tensile loading conditions with in situ Acoustic Emission monitoring. The AE data were successfully classified using Unsupervised Pattern Recognition Algorithms and the resulted clusters were correlated to the dominant damage mechanisms of the material. The evolution in time of the different damage mechanisms is feasible after the pattern recognition classification. Microscopic examination was used to correlate the clusters to the damage mechanism they correspond and thus to provide the failure mode identification based on AE data.  相似文献   

14.
In this study, acoustic emission (AE) analysis method was applied to monitor the damage evolution process of ultra high performance concrete (UHPC) under direct tensile test. Three types of UHPCs, including high strain-hardening UHPC, low strain-hardening UHPC and strain-softening UHPC were investigated. Meanwhile, the crack width developments of UHPCs during the tensile test were measured. Test results show that high strain-hardening UHPC exhibited high ductility by forming multiple microcracks invisible to naked eyes (typically below 0.05 mm) in the strain-hardening stage. The crack width-strain curves indicate that increasing the ultimate tensile strain of UHPC can improve its crack width control ability effectively. The AE analysis method could effectively detect the internal damages of the high strain-hardening UHPC at a strain of 600με. At that time, the crack width was smaller than 0.01 mm that could not be detected by crack width measuring instrument in this study. For three types of UHPCs, damages were generated around the localized crack during the strain-softening stage. In a word, the AE analysis method provides strong evidence to the multiple cracking behavior of UHPC during the strain-hardening stage, and provides a clear explanation to the identical damage evolution mechanism for three types of UHPCs during the strain-softening stage.  相似文献   

15.
The tensile behavior of a unique 2.5 D C/SiC composite and associated damage evolution was characterized by means of acoustic emission (AE) technique. The results show that the stress–strain curves exhibit mostly nonlinear behavior, which corresponds well with the AE activities. All the evolutions of damage characteristics indicate the phenomenon of matrix cracking saturation which is in agreement with AE results. Microstructural observations reveal extensive matrix cracks and the fracture of yarns always occurred in yarn crossover areas due to the unique weave architecture.  相似文献   

16.
Discrimination of acoustic emission (AE) signals related to different damage modes is of great importance in carbon fiber-reinforced plastic (CFRP) composite materials. To gain a deeper understanding of the initiation, growth and evolution of the different types of damage, four types of specimens for different lay-ups and orientations and three types of specimens for interlaminar toughness tests are subjected to tensile test along with acoustic emission monitoring. AE signals have been collected and post-processed, the statistical results show that the peak frequency of AE signal can distinguish various damage modes effectively. After a AE signal were decomposed by Empirical Mode Decomposition (EMD) method, it may separate and extract all damage modes included in this AE signal apart from damage mode corresponding to the peak frequency. Hilbert-Huang Transform (HHT) of AE signals can clearly illustrate the frequency distribution of Intrinsic Mode Functions (IMF) components in time-scale in different damage stages, and can calculate accurate instantaneous frequency for damage modes recognition to help understanding the damage process.  相似文献   

17.
An objective analytical procedure for the investigation of damage mechanisms in the thermoplastic self-reinforced polyethylene (UHMWPE/PE) composites under quasi-static tensile load has been established, using Unsupervised Pattern Recognition (UPR) technique for the clustering task of Acoustic Emission (AE) signals. Focus is on the correlating between the obtained classes and their specific damage mechanisms. This was carried out by waveform visualization and Fast Fourier Transform analysis. Pure resin and fiber bundles were tested to collect typical waveforms of matrix cracking and fiber fracture respectively, in order to label the signal classes in the composites. The evolution process of various damage mechanisms in the composites revealed that the correlating method was effective. The AE characteristics of different damage modes found out in this study can be used as the reference for identifying unknown AE signals in the UHMWPE/PE composites. The established procedure is also potential in the investigation of failure mechanisms for composite materials with UPR technique.  相似文献   

18.
Moisture absorption and durability in water environment are major concerns for natural fibres as reinforcement in composites. This paper presents a study on the influence of water ageing on mechanical properties and damage events of flax–fibre composites, compared with glass–fibre composites. The effects of the immersion treatment on the tensile characteristics, water absorption and acoustic emission (AE) recording were investigated. The water absorption results for the flax–fibre composites show that the evolution appears to be Fickian and the saturated weight gain is 12 times as high that the glass–fibre composites. Decreasing continuously with increasing water immersion time, the tensile modulus and the failure strain of flax–fibre composites are hardly affected by water ageing whereas only the tensile stress is reduced regarding the glass–fibre composites. AE indicate that matrix–fibres interface weakening is the main damage mechanism induced by water ageing for both composites.  相似文献   

19.
The damage evolutions of C/SiC composites fabricated by chemical vapor infiltration with two different sizes of yarns were compared by cyclic tensile load/unload tests accompanied with the acoustic emission (AE) monitoring. The results show that an inflexion was observed in both the evolution of hysteresis characteristics and the corresponding AE curve for composite with fine yarns, which is, however, absent for composite with coarse yarns, suggesting that the former is much closer to the tough material than the latter one. Felicity effect was observed for both composites, which is more pronounced for the composite with coarse yarns due to the large yarn sizes leading to more matrix debris inside the yarns.  相似文献   

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