关键词： 复合材料层合板   自适应Kriging(AK)模型   直接概率积分方法(DPIM)   可靠性分析  

摘要： 近年来,复合材料层合板结构被广泛地应用于航空航天、军工、建筑工程等领域。但是,由于其几何尺寸的不准确性、材料参数的分散性、载荷环境的波动性等不确定性因素的影响,可能会对复合材料层合板结构的可靠性和安全性,以及系统的输出响应产生重大影响。由于复合材料层合板的层间黏结不良、外部应力集中等因素,当复合材料层合板结构的能量释放速率达到层间断裂韧性时,就会发生分层。因此对复合材料层合板结构的分层可靠性进行分析具有重要的意义。目前,对于复合材料层合板结构的可靠性分析主要是采用一阶可靠性方法(first order reliability method,FORM)、二阶可靠性方法(second order reliability method,SORM)和重要性抽样方法(importance sampling,IS)等传统可靠性分析方法,并将其和蒙特卡罗模拟(Monte Carlo simulation,MCS)对比。但是,当复合材料结构不确定性维度高且复杂时,这些方法不仅计算效率太低,而且不能保证其计算精度。相比于传统的可靠性分析方法,可以利用基于自适应Kriging模型集成策略和主动学习函数结合蒙特卡罗模拟(adaptive Kriging-based Monte Carlo simulation,AK-MCS)的方法,对复合材料层合板结构进行可靠性分析。而直接概率积分方法(direct probability integral method,DPIM)具有更高的计算效率和精度,特别是对于高维度和复杂的可靠性分析问题。所以,本文采用AK-MCS方法和DPIM对模式Ⅰ、模式Ⅱ和混合Ⅰ/Ⅱ模式下的复合材料层合板结构分层的可靠度进行了研究。结果表明:DPIM和AK-MCS与传统可靠性分析方法相比具有更高的计算精度和计算效率,但是DPIM以其高效的计算效率脱颖而出,尽管其精度略低于AK-MCS,但在处理随机变量更多、非线性程度更高的混合Ⅰ/Ⅱ模式下的层合板结构分层的可靠性时展现出明显优势。综合考虑精度与时效性的平衡,DPIM能够准确地评估复合材料结构的可靠度,保障其在航天航空装备等领域的安全运行。

关键词： 超高韧性水泥基复合材料   耐久性   冻融循环   氯离子腐蚀   收缩徐变  

摘要： 超高韧性水泥基复合材料(Ultra-High Toughness Cementitious Composites,简称UHTCC)作为一种新型工程材料,凭借其优异的力学性能和耐久性,已在土木工程领域获得广泛应用。本文通过系统研究,重点分析了UHTCC在抗冻融循环性能、耐氯离子侵蚀性能和收缩徐变特性三个关键耐久性指标方面相较于普通混凝土的显著优势。研究结果可为UHTCC在实际工程中的材料选型、结构设计和工程应用提供重要的理论依据和技术指导。

关键词： 钾离子电池   过渡金属碳/氮化物   阳极   碳化钛  

摘要： 过渡金属碳/氮化物(MXenes)因其可调的层间距和高导电性,被视为钾离子电池的理想电极候选材料.但合成时间长和相邻层的自聚集限制了其实际应用.采用微波刻蚀将刻蚀时间从几十小时缩短至30 min,同时制备出了高质量的超薄柔性MXenes.以柔性MXenes导电层为基底,将碳球均匀支撑于层间,并通过进一步的硫掺杂诱导了不同钛价态.结果表明:精心设计的S-C@Ti_(3)C_(2)T_(x)阳极在500 mA·g^(-1)的电流密度下,循环400次后显示出327 mA·h·g^(-1)的优异可逆比容量.这是首次将微波蚀刻分层的MXenes材料应用于钾离子充电电池研究中.

关键词： SnS_(0.5)Se_(0.5)   静电纺丝   负极材料   钠离子电池  

摘要： 通过静电纺丝和退火工艺设计并合成了SnS_(0.5)Se_(0.5)纳米粒子偶联N/S/Se三掺杂碳纳米纤维复合材料(SnS_(0.5)Se_(0.5)@NSSe-C).SnS_(0.5)Se_(0.5)和NSSe-C的协同效应使得SnS_(0.5)Se_(0.5)@NSSe-C纳米纤维在高电流密度下具有高可逆容量和超长循环寿命.此外,理论计算进一步表明SnS_(0.5)Se_(0.5)@NSSe-C复合材料具有较高的Na+吸附能,能够表现出更加优异的离子传输性能.本研究为三元锡基硫族化合物的合成提供了新的思路,并有助于研究其反应动力学.

关键词： 银耳多糖   Pickering乳液   乳液稳定性   流变学  

摘要： 目的探究银耳多糖(Tremella fuciformis polysaccharide,TFP)对大豆油Pickering乳液的稳定作用及机制。方法构建TFP大豆油Pickering乳液,通过对乳液的粒径分布、流变学特性、热稳定性及贮藏稳定性等特性进行表征,系统分析TFP浓度对乳液特性的影响。结果显微观察和粒径分析表明,当TFP浓度为0.5%时,液滴尺寸最小,均一性最高。流变学分析显示TFP大豆油Pickering乳液呈假塑性流体特征,乳液黏度随温度升高明显下降,而TFP浓度提高则增加了乳液的黏度,尤其当剪切速率为0.1 s^(-1)时,TFP浓度为0.5%时乳液表观黏度达516.4400 mPa·s,是浓度为0.1%时的45倍。在TFP浓度为0.4%和0.5%时,经95℃热处理30 min后,乳液稳定性仍达(99.03±0.15)%和(91.38±0.70)%,粒径保持稳定,表明乳液的热稳定性较好;储藏14 d后,0.5%浓度的TFP Pickering乳液无分层现象,显示出优异的贮藏稳定性。TFP大豆油Pickering乳液的稳定性与TFP浓度呈正相关。结论TFP通过界面膜增强和空间位阻效应抑制液滴聚集,从而提高Pickering乳液的稳定性。本研究可为多糖类乳化稳定剂的开发应用提供理论支持和实验参考。

关键词： Titanium dioxide  

摘要： The multi-walled carbon nanotubes (MWCNTs) and anatase nano-titanium dioxide (NT) are excellent fillers for the preparation of self-sensing cement-based materials. Moreover, compared with ordinary Portland cement, sulfoaluminate cement has the advantages of low carbon, corrosion resistance and rapid strength development, and the cement-based material can obtain more stable self-sensing performance when used as a matrix. Therefore, this paper prepared sulfoaluminate cement mortar specimens using NT and MWCNTs in either single-addition or double-addition form. Then, the effects of different conductive fillers on the mechanical properties, electrical properties and self-sensing properties of the sulfoaluminate cementitious composites were studied at 3 d curing, and the mechanisms were analyzed by SEM-EDS. The results show that the early mechanical properties of sulphoaluminate cementitious composites were significantly improved by adding NT. Compared to the control group, the compressive strength, flexural strength, splitting tensile strength, and compressive toughness of the cementitious composites with NT increased by 28.36%, 10.67%, 47.76%, and 9.53%, respectively. The single-addition of MWCNTs has the most significant effect on improving the conductivity. Compared with the control group, the direct current (DC) resistivity and alternating current (AC) resistivity at a frequency of 100 kHz decreased by 46.91% and 63.87%, respectively. The double-addition of MWCNTs-NT has the most significant effect on improving the self-sensing properties of the sulfoaluminate cementitious composites. Compared with the control group, the maximum fractional change in resistivity, stress and strain sensitivity of the sulfoaluminate cementitious composites with MWCNTs-NT under monotonic compression load and splitting tensile load increased by 235%, 211%, 313%, and 44%, 65%, 648%, respectively. SEM-EDS showed that in terms of compactness, the mortar with NT> control group> mortar with M

关键词： Extrusion  

摘要： Multi-layer flexible and stretchable electronics have great potential in fields such as biomedicine, wearable devices, and electronic skin. However, the development and application of multi-layer flexible and stretchable electronics are hindered by issues such as poor conductivity, low stretchability, and difficulties in manufacturing interlayer interconnects. In this paper, a highly conductive stretchable composite material suitable for direct extrusion 3D printing of interlayer interconnecting wires was prepared by flexibly adding diethylene glycol (DEG) additives within the composite conductive materials of silver nanoparticles (AgNP), multi-walled carbon nanotubes (MWCNT) and polydimethylsiloxane (PDMS). Benefiting from the high melting point of DEG, the AgNP in the conductive composites can effectively aggregate and precipitate out of the surface during the curing process, thus improving the electrical conductivity. The good solvent wettability balances the issues of material structure collapse and 3D printer nozzle clogging, facilitating the 3D printing of interlayer interconnects. Meanwhile, the large aspect ratio of MWCNT can stabilize the electrical connection between AgNP during the stretching process. The resulting conductive material exhibits excellent conductivity (104 S·cm−1) and stretchability (Cycling over 1 000 times at 40% strain), which can achieve the printing of stretchable intralayer interconnects, self-supporting 3D vertical interconnects, and 2.5D curved interconnects based on material extrusion 3D printing technology. The stretchable composite paste developed in this study demonstrates good performance in flexible electrothermal heating and flexible display arrays, confirming the promising application prospects of stretchable conductive composite materials in the field of flexible and stretchable electronics, paving the way for the development of 3D printed multi-layer flexible and stretchable electronics. © 2025 Beijing University of Aerona

关键词： Shear strength  

摘要： The interfacial properties of high-modulus carbon fiber (HMCF) composites have always been the key to their applications, and surface modification of HMCF is one of the important ways to improve the interfacial properties. Graphene nanosheets (GNP) were introduced into the surface of HMCF by electrophoretic deposition, and the surface morphology and surface chemical state of HMCF before and after modification were characterized by SEM and XPS, and the interlaminar shear strength (ILSS) and moisture absorption rate of HMCF reinforced epoxy resin composites before and after modification were tested. The results show that the surface electrophoretic deposition of GNP by HMCF can not only improve the interfacial properties of the reinforced epoxy resin composites, but also reduce the moisture absorption rate of the composites. When the GNP concentration was 0.5 mg/mL and the electrophoretic deposition voltage was 10 V, the interlaminar shear performance of the composites increased by 8.8% to 75.6 MPa, and the moisture absorption rate was reduced by 9.5% compared with the unmodified sample after 30 days of storage at 90℃ and 80% relative humidity (RH), and the interlayer shear performance remained at 67.8 MPa after 60 days of storage. Both interfacial and hygrothermal properties of the modified HMCF comosites have been improved. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.

关键词： Hydrogen bonds  

摘要： Carbon fiber reinforced composites (CFRP) have the advantages of light weight, high strength, corrosion resistance, fatigue resistance and wear resistance, and have become a new advanced structural materials for marine engineering. In this paper, the effects of hygrothermal aging on the thermal/mechanical (tensile, flexural and short-beam shear properties) and frictional wear properties of CFRP were investigated. Combined with the analysis of micro-morphology and structure, the degradation mechanisms of mechanical and frictional wear properties of CFRP immersed in the distilled water at 60℃ for up to 90 d were revealed. It was found that the maximum degradation amplitudes of CFRP tensile, flexural and short-beam shear strengths were 5.8%, 13.0%, and 20.9%, due to the destruction of hydrogen bonds and partial covalent bonds of polymer resin chains by water molecules during the hygrothermal aging process, which resulted in the defect creation and the lateral restraint loss of the fiber bundles within the CFRP, ultimately leading to the de-bonding of fiber/resin interfaces. In addition, the thermodynamic and viscoelastic behavior of CFRP in the hygrothermal environment exhibited a nonlinear change, attributing to the coupling effects of positive resin post-curing and negative hygrothermal aging. Compared with those before immersion, the average coefficient of frictions (COFs) of CFRP aged for 15, 30, 60, and 90 d decreased by 23.8%, 35.0%, 43.7% and 53.8%, respectively, which was attributed to the friction lubrication of water molecules inside the diffused CFRP acting as friction lubricants during friction, alleviating the wear of the CFRP/abrasive ball interface. The wear rate (Ws) and wear scar width (WSW) of CFRP aged for 90 d increased by 254.6% and 114.9% compared with that before aging, which was attributed to the fact that the water molecules forming new hydrogen bonds with the resin matrix were in the bonded water state, reducing inter-chain force between resin

关键词： Carbon/phenolic composites   Machine learning   Linear ablation rate   Surface roughness  

摘要： In thermal protection structures, controlling and optimizing the surface roughness of carbon/phenolic (C/Ph) composites can effectively improve thermal protection performance and ensure the safe operation of carriers in high-temperature environments. This paper introduces a machine learning (ML) framework to forecast the surface roughness of carbon-phenolic composites under various thermal conditions by employing an ML algorithm derived from historical experimental datasets. Firstly, ablation experiments and collection of surface roughness height data of C/Ph composites under different thermal environments were conducted in an electric arc wind tunnel. Then, an ML model based on Ridge regression is developed for surface roughness prediction. The model involves incorporating feature engineering to choose the most concise and pertinent features, as well as developing an ML model. The ML model considers thermal environment parameters and feature screened by feature engineering as inputs, and predicts the surface height as the output. The results demonstrate that the suggested ML framework effectively anticipates the surface shape and associated surface roughness parameters in various heat flow conditions. Compared with the conventional 3D confocal microscope scanning, the method can obtain the surface topography information of the same area in a much shorter time, thus significantly saving time and cost.