今日更新:Composite Structures 1 篇,Composites Part A: Applied Science and Manufacturing 1 篇,Composites Part B: Engineering 2 篇
A decoupled bend-tension-shear coarse grained model for staggered structures
Yanan Zhang, Haiyi Liang
doi:10.1016/j.compstruct.2024.118688
交错结构的弯曲-拉伸-剪切解耦粗粒模型
Biomaterials like teeth, bone, and nacre have developed curved geometry and staggered structures, with remarkable mechanical properties attracting plenty of theoretical and numerical works. For these brick–mortar materials, the coupling between bending, stretching, and shearing deformations is inevitable under transverse loading and remains to be explored. In this work, we propose a decoupled bend-tension-shear (d-BTS) coarse grained model for staggered structures, using node displacements only as the basic variables. The bending and stretching deformations of bricks are modeled by two independent sets of springs tied together by Lagrange multipliers, leading to improved computation efficiency. This model may reduce to a minimal model with the least number of spring nodes characterizing the coupling between bending, stretching, and shearing deformations, analogous to the widely accepted tension-shear-chain (TSC) minimal model developed for shear-lag deformation in staggered structures. d-BTS model is validated with several examples confirmed by finite element calculations. The model is used to simulate the three-point bending tests, revealing the important contribution of bending to shear strain and the nontrivial roles of break-matrix on bending rigidity. d-BTS model presents a simple and efficient tool to investigate the toughness and strength of staggered structures in large scales when subjected to bending and stretching.
牙、骨、珠质等生物材料已经发展出弯曲几何和交错结构,具有显著的力学性能,吸引了大量的理论和数值研究。对于这些砖砂浆材料,在横向荷载作用下,弯曲、拉伸和剪切变形之间的耦合是不可避免的,有待进一步研究。在这项工作中,我们提出了一种解耦的弯曲-拉伸-剪切(d-BTS)粗粒度模型,用于交错结构,仅使用节点位移作为基本变量。通过拉格朗日乘法器将两组独立的弹簧组合在一起来模拟砖块的弯曲和拉伸变形,从而提高了计算效率。该模型可以简化为具有最少数量的弹簧节点的最小模型,表征弯曲、拉伸和剪切变形之间的耦合,类似于广泛接受的用于交错结构剪切滞后变形的张力-剪切链(TSC)最小模型。通过有限元计算验证了d-BTS模型的正确性。利用该模型模拟了三点弯曲试验,揭示了弯曲对剪切应变的重要贡献以及断裂矩阵对弯曲刚度的重要作用。d-BTS模型为研究大尺度交错结构在弯曲和拉伸作用下的韧性和强度提供了一种简单有效的工具。
Role of fiber clustering and resin bleeding on voids and evolution of fiber volume fraction for additively manufactured continuous carbon fiber thermoset composites with dual-cure resins
Shaharear Md Emtiaz, Maximilian Pitto, Pavel Šimáček, Suresh G Advani
doi:10.1016/j.compositesa.2024.108601
增材制造双固化连续碳纤维热固性复合材料中纤维聚集和树脂渗出对空隙的影响及纤维体积分数的演变
Additive manufacturing of continuous fiber-reinforced thermosets is enhanced by producing a core–shell structured tow, where admixed UV and thermal cure resin (dual-cure) forms an interpenetrating polymer network. Such material can be produced by rapid interlayer curing assisted (RICA) 3D printing, a process that impregnates a fiber tow with epoxy and then applies a dual-cure resin coating hardened by UV exposure. A challenge of this novel process is the fiber volume fraction control and void content minimization after dual-cure coating, UV curing and consolidation. Here we reveal towpreg properties at RICA processing points of interest via a continuous model setup. We also put in place metering of the resin during the process which increased the fiber volume fraction and provided better layer thickness control. Two new numerical models were introduced that investigate (i) the void formation during impregnation of clustered carbon fibers and (ii) void filling accompanied by resin bleeding from core-shell structured tows during compaction. Experimental results revealed clusters in the carbon fiber tow during roller-assisted epoxy impregnation, with a void content between 3% and 5%. The clustering model showed that large clusters entrapped bigger voids. After consolidation, void content was reduced to 2.1–2.7% when the shell only contained UV resin, thanks to resin entrapment by the cured shell. Resin bled from the dual-cure shell, which reduced void filling but increased the fiber volume fraction from 0.29 up to 0.37. Ultimately, this work demonstrates that the dual-cure coating mixture utilized for RICA 3D printing has an effect on the final void content that is amplified during high-speed consolidation and reduced when the incoming initial voids are small.
连续纤维增强热固性材料的增材制造通过生产核壳结构束来增强,其中混合UV和热固化树脂(双固化)形成互穿聚合物网络。这种材料可以通过快速层间固化辅助(RICA) 3D打印来生产,该工艺在纤维束中浸渍环氧树脂,然后涂上一层通过紫外线照射硬化的双固化树脂涂层。该工艺面临的挑战是双固化涂层、UV固化和固结后纤维体积分数的控制和空隙含量的最小化。在这里,我们通过连续模型设置揭示了在RICA处理感兴趣点的towpreg属性。我们还在加工过程中对树脂进行了计量,这增加了纤维体积分数,并提供了更好的层厚控制。引入了两个新的数值模型来研究(i)在簇状碳纤维浸渍过程中的空隙形成和(ii)在压实过程中由核-壳结构束产生的树脂渗出的空隙填充。实验结果表明,在辊助环氧树脂浸渍过程中,碳纤维束中出现了团簇,空隙率在3% ~ 5%之间。聚类模型表明,大的聚类捕获更大的空隙。固化后仅含UV树脂时,由于树脂被固化后的外壳包裹,孔隙率降低到2.1-2.7%。树脂从双固化壳中渗出,减少了空隙填充,但使纤维体积分数从0.29提高到0.37。最后,这项工作表明,用于RICA 3D打印的双固化涂层混合物对最终孔隙含量有影响,在高速固结时,最终孔隙含量会增加,而当进入的初始孔隙很小时,最终孔隙含量会减少。
Decoupling enhancements of breakdown strength and dielectric constant in PMIA-based composite films for high-temperature capacitive energy storage
Wenqi Zhang, Xin Xu, Sidi Fan, Zhen Zhang, Dan Wu, Xiao Yang, Rui Yang, Kaixuan Sun, Fangcheng Lv, Xiang Yu
doi:10.1016/j.compositesb.2024.112013
高温电容储能用pmia基复合薄膜击穿强度和介电常数的解耦增强
Polymer-based dielectric films are increasingly demanded for capacitive energy storage. However, the negative coupling between dielectric constant (ɛr) and breakdown strength (Eb) presents a significant challenge to further enhancements, especially at high temperatures. Here, we propose dielectric composite films employing poly(m-phenylene isophthalamide) (PMIA) as the matrix, with nanodiamond (ND) particles modified by polydopamine (PDA) serving as reinforcing fillers. At 150°C, the 1.0 wt% film demonstrates an ultrahigh discharge energy density (Ue) of 5.15 J/cm3 at a charge-discharge efficiency (η) exceeding 90%. Even the temperature increases to 200°C, the film maintains a desirable Ue of 2.36 J/cm3 with η > 90%, achieving a record energy storage performance that outperforms numerous previous works. In addition to the inherent hydrogen bonds among PMIA molecular chains, ND@PDA fillers, enriched with hydroxyl groups, facilitate the formation of additional hydrogen bonds with PMIA, generating a hydrogen bonding network. This network provides additional dipoles for overall polarization, enhances Young’s modulus for electromechanical resistance, and suppresses dielectric loss upon temperature increase, thereby reducing conduction loss. Both experimental and simulation results indicate that this hydrogen bonding network is extremely stable at high temperatures, effectively promoting the decoupling enhancements of ɛr and Eb for high-temperature energy storage applications.
基于聚合物的电介质薄膜越来越受到电容能量存储领域的需求。然而,介电常数(εr)与击穿强度(Eb)之间的负耦合构成了进一步提升的重大挑战,尤其是在高温下。在这里,我们提出采用聚(间苯二甲酰异酞胺)(PMIA)作为基体的电介质复合薄膜,采用经过聚多巴胺(PDA)改性的纳米钻石(ND)颗粒作为增强填料。在150℃下,1.0 wt%的薄膜在充电-放电效率(η)超过90%的情况下展现出超高的放电能量密度(Ue)为5.15 J/cm3。即使温度升高到200℃,薄膜仍保持着可接受的Ue为2.36 J/cm3,η>90%,实现了超越众多先前工作的纪录能量存储性能。除了PMIA分子链本身的氢键外,ND@PDA填料丰富的羟基促进了与PMIA形成额外的氢键,形成氢键网络。该网络为整体极化提供了额外的偶极子,增强了电-机械阻力的杨氏模量,并抑制了温度升高引起的介电损耗,从而减少了传导损耗。实验和模拟结果均表明,该氢键网络在高温下极为稳定,有效促进了高溫能量存储应用中εr和Eb的解耦增强。
Growth factor collected cell membrane-functionalized matrix for vascular-innervated bone regeneration
Fangyu Qiao, Yang Zou, Yonggang Lv
doi:10.1016/j.compositesb.2024.112019
生长因子收集的细胞膜功能化基质用于血管神经骨再生
Peripheral nerves and blood vessels regulate the development process of bone tissue by delivering neural and vascular-related cytokines. However, challenge of preventing the loss of neural and vascular growth factors and ensuring their long-term availability for bone defects was often been overlooked. The current study designed a hybrid cell membrane with specific surface receptors for calcitonin receptor (CTR) and vascular endothelial growth factor receptor (VEGFR) through overexpressed the CTR receptor gene (Calcr) and the VEGFR 1 gene (Flt-1). The bone repair matrix functionalized by the hybrid cell membrane (GCMs) had collecting property for neurogenic growth factor (NGF) and vascular endothelial growth factor (VEGF). Furthermore, GCMs enhanced neural and vascular differentiation in mesenchymal stem cells (MSCs) and stimulated osteogenic differentiation of MSCs through neural and vascular-related paracrine signals. GCMs also facilitated the angiogenesis and neurogenesis around bone defects, further promoted the repair of rat skull defects. This study suggests a promising approach for using cell membranes to harvest growth factors for innervation and vascularization in bone reconstruction.
周围神经和血管通过传递神经和血管相关细胞因子来调节骨组织的发育过程。然而,如何防止神经和血管生长因子的丢失,并确保其在骨缺损中的长期可用性,往往被忽视。本研究通过过表达降钙素受体基因(Calcr)和血管内皮生长因子受体1基因(Flt-1),设计了具有降钙素受体(CTR)和血管内皮生长因子受体(VEGFR)特异性表面受体的杂交细胞膜。杂化细胞膜(GCMs)功能化的骨修复基质具有神经源性生长因子(NGF)和血管内皮生长因子(VEGF)的聚集性。此外,GCMs还能增强间充质干细胞(MSCs)的神经和血管分化,并通过神经和血管相关的旁分泌信号刺激MSCs的成骨分化。gcm还能促进骨缺损周围的血管生成和神经发生,进一步促进大鼠颅骨缺损的修复。本研究提出了一种利用细胞膜收集生长因子用于骨重建的神经支配和血管化的有前途的方法。