关键词： Composites   Load transfer   Nacre   Bioinspired   Architected materials  

摘要： Nacre exhibits excellent mechanical properties attributed to the staggered alignment of inorganic minerals and bio-organic materials. This study aims to understand how stress transfers from macro-scale loading conditions to the staggered architecture, revealing multiple stress transfer modes in nacre-like composites under off-axis tensile loading conditions. We propose an innovative off-axis tension-shear chain model, which predicts the trend of the equivalent modulus. Systematic optimization reveals a counter-intuitive result: the equivalent modulus at a certain angle can be smaller than the equivalent moduli in both principal directions, and this phenomenon differs from the monotonic behavior commonly observed in continuous fiber composite materials. © The Chinese Society of Theoretical and Applied Mechanics and Springer-Verlag GmbH Germany, part of Springer Nature 2025.

关键词： Discontinuous curved fiber reinforced composites (DCFRCs)   Representative volume element (RVE)   Modified RSA algorithm   Modified rule-of-mixture   Elastic properties   Fiber waviness  

摘要： The present study proposes a modified random sequential absorption (RSA) algorithm to generate a representative volume element (RVE) model for predicting the elastic properties of discontinuous curved fiber reinforced composites (DCFRCs) with varying fiber waviness functions and orientations. A small-move method was proposed to modify the traditional RSA algorithm. In comparison with the original RSA algorithm, the generation efficiency of the proposed modified RSA algorithm increased by over 40%, and the achievable maximum fiber volume fraction could reach up to 15% with a fiber aspect ratio of 15. The generated RVE model was utilized in conducting finite element analysis to investigate the effect of fiber waviness and wavy functions on the elastic properties of DCFRCs. Finally, a modified rule-of-mixture was proposed to predict the elastic properties of DCFRCs with various fiber orientations. The results indicated that the elastic properties predicted by the modified rule-of-mixture were in good agreement with those obtained from the RVE model, thereby demonstrating its effectiveness.

关键词： High-G droplets   Composite substrate   Wetting profile   Hypergravity condition   Scaling law   Energy distribution  

摘要： The wetting phenomenon of composite substrates in hypergravitational environment has a huge application in electronic devices and astronaut healthcare in aerospace missions. In the present contribution, the governing equation of high-G droplets on the composite substrate is firstly established in the hypergravitational environment. Meanwhile, the apparent contact angles at the contact line between droplets and substrates with different stiffness gradients are achieved. Then, we analyze the effects of hypergravity factor and the substrate stiffness on the wetting profile of high-G droplets. By introducing the droplet volume and contact angle into the Bond number, the scaling law of the high-G droplet profile is established, and we find that the contact radius of the droplet R/S-0.5 has a linear relationship with rho omega(2)rl(2)S/(gamma(LV)theta), while the droplet height H/S-0.5 has a power-law relationship with rho omega(2)rl(2)S / (gamma(LV)theta). Finally, we explain the profiles of high-G droplets during the wetting process by illustrating energy components of the entire system and find that the substrate with positive triangular stiffness and inverted triangular stiffness show opposite evolution laws. On a substrate with inverted triangular stiffness, the gravitational potential energy is more dominant.

关键词： Porous metal-matrix nanocomposite   Graphene nanoplatelets   Rotating microbeams   Modified couple stress theory   Dynamics   Thermal buckling  

摘要： A comprehensive dynamic model for thermal buckling, elastic vibration and transient response analysis of rotating nano-composite porous metal-matrix microbeams reinforced with graphene nanoplatelets (GNPs) under a uniform thermal gradient is proposed. Various pore distribution patterns are considered together with different GNPs dispersion rules according to the specific functions. The extended rule of mixture and Halpin-Tsai micromechanics model are employed to evaluate the effective material properties of the nanocomposites. Based on the modified couple stress theory and the improved third-order shear deformation theory, the dynamic equations of the rotating microbeam are established by the Lagrange's equation. The Chebyshev-based Galerkin method is adopted to discretize these equations, which are then solved by the complex modal analysis and Runge-Kutta-Merson method. Convergence study and comparisons with previous literature are conducted for validation of the present method. A parametric study performed analyzes the effects of angular velocity, thickness-to-length scale parameter ratio, porosity coefficient, weight fraction and geometry of GNPs together with distribution patterns of GNPs and pore on the critical buckling temperature rise, fundamental frequency and time-dependent response of the rotating nanocomposite microbeams. The results reveal significant effects of these parameters on the relevant mechanical behaviors, some of which are even contrary to expectations. Therefore, it is necessary to further study this kind of rotating nanocomposite structures for the optimal design.

关键词： 纳米金颗粒   介孔二氧化硅   钛表面改性   微纳结构   高糖条件   成骨分化  

摘要： 背景:微纳米结构改性是钛种植体表面处理的热点研究领域。糖尿病高血糖环境会影响钛种植体与骨组织形成稳定的结合,探索通过表面微纳结构改性来提高钛种植体在高糖环境下的成骨活性是有必要的。目的:观察钛表面纳米金颗粒@介孔二氧化硅涂层对体外高糖条件下成骨分化的影响。方法:分别制备纳米金颗粒悬浮液与介孔二氧化硅,将二者按一定比例混合在去离子水中,制备纳米金颗粒@介孔二氧化硅悬浮液。取钛片,分3组处理:光滑组经过水砂纸打磨处理,纳米管组经过水砂纸打磨处理后采用阳极氧化技术制备二氧化钛纳米管涂层,实验组制备二氧化钛纳米管涂层后浸泡于纳米金颗粒@介孔二氧化硅悬浮液中,制备纳米金颗粒@介孔二氧化硅涂层,表征3组钛片表面的微观形貌、亲水性。将大鼠骨髓间充质干细胞接种于3组钛片表面,通过细胞活/死荧光染色及CCK-8实验检测细胞增殖,DAPI/鬼笔环肽染色检测细胞黏附。将大鼠骨髓间充质干细胞接种于3组钛片表面,加入高糖成骨诱导培养基培养,通过碱性磷酸酶与茜素红S染色检测成骨分化。结果与结论:(1)扫描电镜下可见光滑组钛片表面均匀平坦,纳米管组钛片表面排列紧密的二氧化钛纳米管阵列,实验组钛片在二氧化钛纳米管表面及内部均负载纳米金颗粒@介孔二氧化硅;纳米管组、实验组钛片亲水性均优于光滑组。(2)细胞活/死荧光染色结果显示,3组钛片表面的细胞活力均高于90%;CCK-8实验结果显示,实验组细胞增殖率高于光滑组、纳米管组;DAPI/鬼笔环肽染色结果显示,二氧化钛纳米管涂层、纳米金颗粒@介孔二氧化硅涂层更有利于细胞黏附。(3)碱性磷酸酶与茜素红S染色结果显示,实验组钛片表面细胞碱性磷酸酶活性与细胞外基质矿化程度均高于光滑组、纳米管组。(4)结果表明,纳米金颗粒@介孔二氧化硅涂层可增强钛表面生物活性,促进高糖环境下的成骨分化。

关键词： Fiber reinforced plastics  

摘要： To analyze the dynamic performance of variable-angle ply porous fiber-reinforced sandwich composite panels under simply supported boundary conditions, the vibration differential equations for the porous double-layer sandwich panels were established based on the layerwise theory and the Rayleigh-Ritz method. These equations were subsequently solved using the Navier method. The dynamic characteristics at various ply angles were analyzed using Abaqus and the modal tests were performed with [0°/90°] and [±45°] ply orientations to validate the accuracy of the theoretical model. A parametric analysis of the porous double-layer sandwich panel was conducted using the theoretical model, followed by structural optimization using a genetic algorithm. The research reveals that laminated panels with a porosity of 94.854% and fiber ply angles in multiples of 45° exhibit outstanding dynamic performance. These results provide a reference for the design and manufacture of such structures. © 2025 Chinese Vibration Engineering Society. All rights reserved.

关键词： Guided electromagnetic wave propagation  

摘要： Structural load can affect propagation of guided waves, thereby inorease the uncertainty of guided wave damage recognition and potentially cause mis-judgment of damage. Here, to reduce effects of structural load on guided wave damage recognition, an improved baseline reconstruction load compensation method was proposed. This method could compensate baseline signal phase to be consistent with current signal phase. The effectiveness of this method was verified with static tensile tests for aluminum plates and damage monitoring of composite T-joints under tensile load. The study results showed that the proposed method can effectively reduce effects of load on phase of guided wave monitoring signals, and correctly detect damage of composite T-joints under tensile load. © 2025 Chinese Vibration Engineering Society. All rights reserved.