今日更新:Composite Structures 1 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Science and Technology 1 篇
Deployment behavior and mechanical property analysis of Kresling origami structure
Ji Zhang, Changguo Wang
doi:10.1016/j.compstruct.2024.118234
Kresling折纸结构展开行为及力学性能分析
Kresling origami, a representative variant of origami, exhibits several distinctive features such as multistable states, changeable stiffness, and compression-torsion coupling deformation. The first focus of this study involves examining the mechanical properties of origami structures, specifically, the equivalent modulus and critical buckling stress during the deployment process are evaluated. Subsequently, the collapsibility of the Kresling origami structure is explicated with regard to energy and strain. In the folding process, when the Kresling angle is 0.0135 rad, the maximum torque is 959 Nmm, and the structure will occur snap-through instability, which is the nonlinear critical buckling load of the failure. After that, the torque decreases rapidly, and then gradually increases slowly. The mechanical model is developed and subsequently evaluated in terms of its flexibility and adjustment of stiffness. The present study investigates the buckling modes and vibration properties of Kresling origami structures, as well as their combination structures. For the buckling of Kresling origami structure, the critical buckling load of Euler buckling is 0.023 N and that of local buckling is 0.67 N. In short, the critical buckling load of the column shell is greater than that of the Kresling origami structure, which is due to the small local stiffness of structure.
Kresling折纸是折纸的一种代表形式,具有多稳态、可变刚度、压扭耦合变形等特点。本研究的第一个重点是检查折纸结构的力学性能,特别是在展开过程中评估等效模量和临界屈曲应力。随后,从能量和应变两个方面阐述了Kresling折纸结构的溃散性。在折叠过程中,当Kresling角为0.0135 rad时,最大扭矩为959 Nmm,结构将发生卡断失稳,这是破坏的非线性临界屈曲载荷。之后,转矩迅速减小,然后逐渐缓慢增大。开发了机械模型,并随后根据其灵活性和刚度调整进行了评估。本文研究了Kresling折纸结构及其组合结构的屈曲模态和振动特性。对于Kresling折纸结构的屈曲,欧拉屈曲的临界屈曲载荷为0.023 N,局部屈曲的临界屈曲载荷为0.67 N。简而言之,柱壳的临界屈曲载荷大于Kresling折纸结构,这是由于结构的局部刚度较小。
On how pseudo-ductility modifies the translaminar fracture toughness of composites and the nominal strength of centre-cracked specimens
A. Subramani, P. Maimí, J. Costa
doi:10.1016/j.compositesa.2024.108275
伪塑性如何改变复合材料的跨层断裂韧性和中心裂纹试件的名义强度
Among the efforts to revert the traditionally brittle characteristic of laminated composites, pseudo-ductility relies on utilising hybridisation to stimulate sub-critical damage mechanisms. However, how such pseudo-ductility would translate into an increase in material toughness or an improvement in the strength of the sub-components remains unclear. To elucidate this, we perform a numerical study departing from a parameterised pseudo-ductile model implemented in a finite element model. We use non-dimensional analysis to investigate the effect of the two most relevant parameters: pseudo-ductile strain ( ɛ d ) and the ratio of ultimate strength to pseudo-ductile yield strength ( σ f / σ y ). We infer material toughness from the simulation of Compact Tension specimens, and it is shown to increase linearly with ɛ d , and non-linearly with σ f / σ y but tends to a plateau. Then, the simulation of Centre Cracked scaled specimens reveal that the nominal strength increases on the elastic limit extreme (large specimens) but decreases below a given size.
在恢复层合复合材料传统脆性特性的努力中,伪延性依赖于利用杂化来刺 激亚临界损伤机制。然而,这种伪延展性如何转化为材料韧性的增加或子部件强度的改善仍不清楚。为了阐明这一点,我们从一个参数化的伪延性模型出发,在一个有限元模型中实现了一个数值研究。我们使用无量纲分析来研究两个最相关参数的影响:伪延性应变(d)和极限强度与伪延性屈服强度之比(σ f / σ y)。材料的韧性随d的变化呈线性增加,随σ f / σ y的变化呈非线性增加,但趋于平稳。然后,对中心裂纹试件进行了数值模拟,结果表明,在弹性极限极限(大试件)上,公称强度增大,但在给定尺寸下,公称强度减小。
All-composite honeycomb-enhanced corrugated hybrid structures to improve flexural responses
Cuiping Bai, Hougai Shi, Qu Yan, Haiying Cao, Wenyi Bao, Xiaofei Li, Hualin Fan
doi:10.1016/j.compositesa.2024.108282
改进弯曲响应的全复合蜂窝增强波纹混合结构
An all-composite corrugated hybrid structure was proposed. The Nomex honeycomb was filled to enhance carbon fiber reinforced polymer (CFRP) corrugated sandwich against mono-corrugation flexural collapse. Three-point bending behaviors of the honeycomb enhanced corrugated sandwich (HECS), taking account of the effects of honeycomb density, loading position, and honeycomb proportion, were investigated. The bearing capacity of the HECS is greatly increased. The mutual constraint between the web and honeycomb exhibits different damage modes from those of corrugated and honeycomb sandwich. The peak load and elastic stiffness of the HECS are 1.37 times and 1.4 times higher than that of unenhanced corrugated sandwich, respectively. Numerical and analytical models were able to consistently predict the deflection and stiffness of the HECS.
提出了一种全复合波纹杂化结构。Nomex蜂窝填充增强碳纤维增强聚合物(CFRP)波纹夹层抗单波纹弯曲崩溃。研究了蜂窝增强波纹夹层结构在考虑蜂窝密度、加载位置和蜂窝比例影响下的三点弯曲行为。该结构的承载能力大大提高。腹板与蜂窝之间的相互约束表现出不同于波纹夹层和蜂窝夹层的损伤模式。其峰值荷载和弹性刚度分别是未增强波纹夹层的1.37倍和1.4倍。数值和解析模型能够一致地预测HECS的挠度和刚度。
Characterization and prediction of frequency- and moisture-dependent damping behaviors for hierarchical flax fiber reinforced composite laminates
Songli Tan, Zhen Zhang, Qian Li, Weidong Yang, Tao Yu, Yan Li
doi:10.1016/j.compscitech.2024.110682
层次化亚麻纤维增强复合材料层合板频率和湿度相关阻尼特性的表征和预测
This study aims to investigate the damping behaviors of unidirectional and laminated flax fiber reinforced composites (FFRCs) under various frequencies and moisture absorption conditions. The damping performances of unidirectional (0°, 45°, 90°), orthotropic and symmetric angle-ply composites were evaluated by the cantilever percussion free-decay method to establish the relationship between frequency, hygroscopicity and damping ratio. To elucidate the frequency- and moisture-dependent damping mechanisms, the glass-transition temperature and modal analysis were examined using dynamic mechanical analysis and a 3D scanning laser Doppler vibrometer respectively. To predict the frequency- and moisture-dependent damping behaviors for hierarchical FFRC laminates, a finite element model subject to the damping test was developed by integrating laminate theory and the complex eigenvalue method in a user-defined material subroutine. The findings indicate that moisture absorption leads to an increase in the damping ratio and changes the frequency-dependent trend. The distinct hierarchical structures of flax yarns result in strong frequency- and moisture-dependent damping performances in FFRC laminates. A significant agreement between the experimental modal frequency, damping ratio, mode of vibration of all composites and those values derived from the established modelling was achieved. It offers a foundational parameter for precisely predicting the damping properties of FFRC laminates with complex stacking sequences and designing safe and reliable FFRC structures integrating load-bearing and damping functionalities.
研究了不同频率和吸湿条件下单向和层压亚麻纤维增强复合材料(ffrc)的阻尼特性。采用悬臂冲击自由衰减法对单向(0°、45°、90°)、正交各向异性和对称角层复合材料的阻尼性能进行了评价,建立了频率、吸湿性和阻尼比之间的关系。为了阐明频率和湿度相关的阻尼机制,分别使用动态力学分析和三维扫描激光多普勒振动仪对玻璃化转变温度和模态进行了分析。为了预测层次化FFRC层合板的频率和湿度相关阻尼行为,在自定义材料子程序中,将层合板理论与复特征值法相结合,建立了一个阻尼试验的有限元模型。结果表明,吸湿导致阻尼比增大,并改变了频率依赖趋势。亚麻纱独特的层次结构使得FFRC层压板具有较强的频率依赖性和湿度依赖性阻尼性能。所有复合材料的实验模态频率、阻尼比、振动模态与建立的模型得出的值之间具有显著的一致性。为精确预测复杂叠置顺序的FFRC层合板的阻尼特性,设计安全可靠的集承载和阻尼功能于一体的FFRC结构提供了基础参数。