含孔隙形态分布特征的孔隙率超声衰减测试建模

借助显微照相分析系统,对碳纤维复合材料孔隙形态特征进行观察和统计分析.结果表明,复合材料孔隙形态特征与孔隙含量存在着密切关系,孔隙长度特征参数近似呈对数正态分布,并建立了含孔隙形态分布特征的孔隙率超声衰减测试模型.     

Comparative study of two lay-up sequence dispositions for flexible skin design of morphing leading edge

Morphing leading edge has great potential for noise abatement and aerodynamic efficiency improvement. The drooping effect is realized by bending of the flexible skin which encloses to form the leading edge. Since the flexible skin is often made of composite laminates of Glass Fiber Reinforced Plastics (GFRP), the lay-up sequences have become the determinant, which affects not only the morphing quality but also the manufacturing complexity. Two optimizing methods of lay-up sequences are comparatively studied. In the first method, the laminal quantities in 0°, ±45° and 90° vary independently, while in the second one, the concept of isotropic laminate unit [0/45/−45/90]s is employed and the unit quantity is the unique variable. Final evaluation demonstrates that for both methods there is insignificant impact to the overall morphing quality; however, specific concern is equally necessary for these two methods to the tip of the leading edge where the skin is at its minimum thickness and bears the most severe bending deformation. In terms of computational efficiency and post-processing labor, the second method has better performance.     

缺陷形式对泡沫塑料拉伸强度的影响

针对几种密度的无缺陷和含缺陷的硬质聚氨酯泡沫塑料试件进行了拉伸实验,研究了材料的强度性质,并且探讨了各种缺陷形式对拉伸强度的影响.实验结果表明,材料经长期放置后(约6年)其拉伸强度并未发生明显的变化,且与相对密度的二次幂成正比;此外,发现缺陷形式对聚氨酯泡沫塑料的拉伸强度有明显的影响,且弧形缺陷对材料拉伸强度的影响具有明显的尺寸效应.      

复合泡沫塑料力学行为模拟的ANN方法

对人工神经网络(ANN)方法在复合泡沫塑料力学行为模拟中的应用进行了研究.首先,选取影响材料力学行为的因素和所需模拟、预测的力学性能作为输入、输出量;然后,利用反向传播算法建立了四层神经网络模型,对复合泡沫塑料的力学性能和本构关系进行了模拟和预测.数值结果表明,训练后的神经网络模型能较好地模拟、预测材料的模量、屈服强度和不同应变率及不同温度下的压缩应力-应变曲线.此外,3种不同改进训练方法的比较说明,Bayesian规则化法的泛化能力最好,LM法收敛最快,而自适应梯度下降动量法则需要较长的迭代时间才能达到相同的精度.      

两种增强泡沫塑料静动态力学性能的比较

通过静、动态压缩实验对两种增强聚氨酯泡沫塑料的压缩力学性能进行了研究，分析了两种材料应力－应变曲线的特点，并比较它们的应变率敏感性和动态加载时的能量吸收特性，实验结果表明：玻璃纤维束增强聚氨酯泡沫塑料具有不同于单丝玻璃纤维增强泡沫塑料的力学性能和变形破坏机制，单丝玻璃纤维增强泡沫塑料具有较好的增强效果。     

VISCO-ELASTIC (PLASTIC) EFFECTS AND FAILURE BEHAVIOR OF PUR FOAMED PLASTICS

ＶＩＳＣＯ┐ＥＬＡＳＴＩＣ（ＰＬＡＳＴＩＣ）ＥＦＦＥＣＴＳＡＮＤＦＡＩＬＵＲＥＢＥＨＡＶＩＯＲＯＦＰＵＲＦＯＡＭＥＤＰＬＡＳＴＩＣＳＬｕＺｉｘｉｎｇ（卢子兴）（ＩｎｓｔｉｔｕｔｅｏｆＳｏｌｉｄＭｅｃｈａｎｉｃｓ，ＢｅｉｊｉｎｇＵｎｉｖｅｒｓｉｔｙｏｆ...     

硬质泡沫喷管堵盖试验及研究

介绍了固体火箭发动机喷管硬质泡沫塑料堵盖的设计方法与试验过程。某型号发动机硬质泡沫喷管堵盖打开压强模拟点火试验结果表明,这种硬质泡沫喷管堵盖设计方案可行。并已在实际中得到应用。     

整体式玻璃钢无人机机翼的研制

通过对整体机翼结构、材料的分析,获得了较为完善的整体玻璃钢机翼的制造方案,并成功应用于某型无人机上。     

用微分法及Mori-Tanaka法求解 复合泡沫塑料的有效模量

基于微分法和Mori-Tanaka方法提出了两种预测含空心球复合材料有效模量的方法;提出利用多次单相夹杂的方法来预测多相颗粒增强复合材料的有效模量;并利用以上的两种方法,求解了含空心球复合泡沫塑料的有效模量.结果表明,理论预测结果和实验结果吻合得较好.同时讨论了空心玻璃微珠相关因素对复合材料有效模量的影响.     

Performance Improvement Method of CFRP with Embedded Optical Fiber

Optical fiber-based sensors are usually applied in structural health monitoring(SHM)as part of smart materials.The weak interface between the optical fiber and the host material will reduce the mechanical performance of the smart materials.Normally,the principal parts of the optical fibers are inorganic,while the matrix of host material is organic.These two kinds of materials can not be combined.Micro-fracture can be found in smart materials.Two methods for improving the interface are proposed.Firstly,the influence of the interface size on the strength is studied.Secondly,interfacial treatment before embedding the optical fiber into the composite is analyzed.Compressive tests of composite laminated specimens are conducted to evaluate the proposed methods.The specimens are produced from T300Carbon/epoxy prepreg,with different treated optical fiber embedded inside.The experimental results indicate that smaller interface size and proper treatment will strengthen the whole structure.