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【新文速递】2024年2月18日复合材料SCI期刊最新文章

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今日更新:Composite Structures 1 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Part B: Engineering 1 篇,Composites Science and Technology 1 篇

Composite Structures

On the nonlinear dynamics and flutter response of hybrid shape memory alloy composite beams

Qianlong Zhang, Fabio Semperlotti

doi:10.1016/j.compstruct.2024.117973

论混合形状记忆合金复合梁的非线性动力学和扑动响应

This study presents a theoretical and numerical investigation of the dynamic response of a hybrid SMA composite beam. Particular emphasis is given to the evaluation of the equivalent damping, the aeroelastic stability, and the possibility to tune the composite’s dynamics by means of pre-strain applied locally to the SMA layers. The model of the hybrid composite beam (HCB) accounts for both the material nonlinearity associated with the phase transformation of the SMA and the geometric nonlinearity (in the von Kármán sense) due to potentially large displacements. The nonlinear governing equations of the HCB are solved by the finite element method and the dynamic behavior of the HCB is assessed for different design parameters, such as thickness, position, and pre-strain level of the SMA layers. Results help understand the role played by the different design parameters in improving the dynamic characteristics of the HCB, with particular attention to effective damping. Furthermore, it is of particular interest to understand the aeroelastic stability of hybrid layered composites due to their widespread applications in aerospace engineering. A simplified model of the nonlinear flutter response of the HCB under supersonic flow conditions is presented and analyzed with particular emphasis on bifurcations and limit cycle oscillations.

本研究对混合 SMA 复合梁的动态响应进行了理论和数值研究。其中 特别强调了对等效阻尼、气动弹性稳定性的评估,以及通过在 SMA 层局部施加预应变来调整复合材料动态响应的可能性。混合复合梁(HCB)模型考虑了与 SMA 相变相关的材料非线性以及潜在大位移导致的几何非线性(von Kármán)。采用有限元法求解 HCB 的非线性控制方程,并根据不同的设计参数(如 SMA 层的厚度、位置和预应变水平)评估 HCB 的动态行为。研究结果有助于了解不同设计参数在改善 HCB 动态特性方面的作用,尤其是有效阻尼。此外,由于混合层状复合材料在航空航天工程中的广泛应用,了解它们的气动弹性稳定性尤其重要。本文提出并分析了混合层状复合材料在超音速流动条件下的非线性扑翼响应简化模型,并特别强调了分岔和极限循环振荡。


Composites Part A: Applied Science and Manufacturing

Preparation of a water-based carboxylated Poly(phthalazione ether nitrile) sizing agent for interfacial reinforcement of CF/PPESK composites

Heming Wang, Shan Cheng, Jingyao Feng, Qingguang Bao, Jiangang Liu, Bing Wang, Binlin Jiang, Zaiyu Wang, Nan Li, Xigao Jian

doi:10.1016/j.compositesa.2024.108091

制备用于 CF/PPESK 复合材料界面加固的水基羧基聚(酞嗪醚腈)施胶剂

This study focuses on synthesizing a range of hydrolysis-modified poly(phthalazione ether nitrile) polymers with different quantities of carboxyl groups (HPPEN-COOH). These polymers are intended to enhance the bonding strength between carbon fibers (CFs) and poly(phthalazine ether sulfone ketone) (PPESK). The chemical structure of HPPEN-COOH was elucidated using FTIR spectroscopy, and the presence of HPPEN-COOH as a coating on the CFs surface was confirmed by XPS analysis. Compared with the UCF/PPESK composite, the interlaminar shear strength of the CF-5/PPESK composite increased by 39%. In the DMA test, the service temperature and storage modulus of the CF-5/PPESK composite were increased to 268°C and 112 GPa, respectively. Furthermore, the composite showed satisfactory performance in hydrothermal aging studies. This method is simple and easy to implement, has the potential for large-scale industrial production, and is an environmentally friendly method to improve the interface properties of the CF/PPESK composite.

本研究的重点是合成一系列具有不同数量羧基(HPPEN-COOH)的水解改性聚(酞嗪醚腈)聚合物。这些聚合物旨在增强碳纤维(CF)与聚(酞嗪醚砜酮)(PPESK)之间的粘合强度。利用傅立叶变换红外光谱阐明了 HPPEN-COOH 的化学结构,并通过 XPS 分析证实了 HPPEN-COOH 作为涂层存在于碳纤维表面。与 UCF/PPESK 复合材料相比,CF-5/PPESK 复合材料的层间剪切强度提高了 39%。在 DMA 测试中,CF-5/PPESK 复合材料的使用温度和储存模量分别提高到 268°C 和 112 GPa。此外,该复合材料在水热老化研究中也表现出令人满意的性能。该方法简单易行,具有大规模工业化生产的潜力,是一种改善 CF/PPESK 复合材料界面性能的环保方法。


A novel phosphorus/nitrogen-containing vinyl imidazolium ionic liquid for improving flame retardancy and mechanical properties of vinyl ester resin, and its carbon fiber composites

Zeqi Zhang, Xue Bi, Wenchao Zhang, Rongjie Yang

doi:10.1016/j.compositesa.2024.108092

 

一种新型含磷/氮乙烯基咪唑离子液体,用于改善乙烯基酯树脂及其碳纤维复合材料的阻燃性和机械性能

In daily life, the application of vinyl ester resin (VER) and its carbon fiber composites is limited by their flame retardancy and mechanical properties. In this work, we synthesized an ionic liquid, VIDHP, from diethyl hydroxymethyl phosphate (DHP) and 1-vinylimidazole (VIM). VIDHP can not only cross-links with VER but also enhances the interaction between the resin and the carbon fiber. The flame retardancy and mechanical properties of VER and its carbon fiber composites were effectively improved by the addition of VIDHP. In particular, the addition of 15 wt% VIDHP increased the flexural strength and flexural modulus of the carbon fiber composites by 29.3 % and 42.4 %, while reducing the total heat release and total smoke release by 15.4 % and 18.4 %. The flame retardant mechanism of VIDHP was also investigated. This approach provides a new idea to improve the flame retardant and mechanical properties of VER and its carbon fiber composites.

在日常生活中,乙烯基酯树脂(VER)及其碳纤维复合材料的应用因其阻燃性和机械性能而受到限制。在这项工作中,我们用羟甲基磷酸二乙酯(DHP)和 1-乙烯基咪唑(VIM)合成了一种离子液体 VIDHP。VIDHP 不仅能与 VER 交联,还能增强树脂与碳纤维之间的相互作用。通过添加 VIDHP,VER 及其碳纤维复合材料的阻燃性和机械性能得到了有效改善。特别是,添加 15 wt% 的 VIDHP 后,碳纤维复合材料的抗弯强度和抗弯模量分别提高了 29.3% 和 42.4%,而总放热量和总释烟量则分别降低了 15.4% 和 18.4%。此外,还研究了 VIDHP 的阻燃机理。这种方法为提高 VER 及其碳纤维复合材料的阻燃性和机械性能提供了新思路。


Composites Part B: Engineering

Winding pattern design of composite cylinders considering the effect of fiber stacking

Yuchen Dai, Chuanxiang Zheng, Jiao Lin, Yangtao Liu, Dawei Wang, Jinjie Lu

doi:10.1016/j.compositesb.2024.111306

考虑纤维堆叠效应的复合材料圆柱体缠绕模式设计

Winding pattern design is a critical step in the production of composite cylinders. Traditional design methods often overlook the impact of stacking fibers layer by layer, leading to deviations between the actual and intended winding trajectories. To ensure consistence between the actual winding outcomes and design objectives, the effect of fiber stacking on the winding patterns was examined in this study. Two winding pattern design methods were proposed: the fixed tangent-point method (FTPM) and the minimum center angle deviation method (MCADM). A comparison was conducted on the variations in the number of tangent points, thread guide round trips, and the radius of the polar hole under the two different methods. Winding experiments were then employed to verify the feasibility of these approaches. The results showed that fiber stacking on the dome was the main reason for the change in winding patterns. Priority can be given to schemes within the design overlap domain for the design of multi-layer winding patterns. While FTPM ensures consistent fiber coverage and tape spacing, it may lead to hole expansion. Additionally, applying multiple layers can alter the dome's shape significantly from the original design. In contrast, MCADM offers slightly variable fiber coverage and spacing without causing hole expansion, achieving the desired dome shape more accurately.

缠绕模式设计是生产复合材料圆筒的关键步骤。传统的设计方法往往会忽略纤维逐层堆叠的影响,从而导致实际缠绕轨迹与预期缠绕轨迹之间出现偏差。为确保实际缠绕结果与设计目标保持一致,本研究探讨了纤维堆叠对缠绕模式的影响。研究提出了两种卷绕模式设计方法:固定切点法(FTPM)和最小中心角偏差法(MCADM)。比较了两种不同方法下切线点数量、导线往返次数和极孔半径的变化。然后通过缠绕实验来验证这些方法的可行性。结果表明,穹顶上的纤维堆叠是造成缠绕模式变化的主要原因。在设计多层缠绕模式时,可优先考虑设计重叠域内的方案。虽然 FTPM 可确保一致的纤维覆盖率和带间距,但它可能会导致孔扩大。此外,应用多层缠绕会大大改变圆顶的形状,使其与原始设计大相径庭。相比之下,MCADM 可提供略微可变的纤维覆盖范围和间距,而不会导致孔扩展,从而更精确地实现所需的圆顶形状。


Composites Science and Technology

Mesoscale modeling of woven composite twisted structures combining digital element embedded model and affine transform

Zengfei Liu, Jingran Ge, Hao Li, Xiaodong Liu, Bing Wang, Jun Liang

doi:10.1016/j.compscitech.2024.110504

 

结合数字元素嵌入模型和仿射变换的编织复合扭曲结构中尺度建模

The mesoscale model with realistic yarn geometries could improve the accuracy of property prediction of woven composite structures. This paper aims to propose a novel mesoscale modeling method for the woven composite twisted structures. Firstly, the torsional deformation of the yarns in the unit cell model is simulated with high-fidelity using digital element fibers embedded into the matrix solid meshes. Then, the solid geometry model of the twisted composite structures is reconstructed from the digital element deformation model by combining the affine transforms. Finally, the elastic responses of the twisted composite structure under cantilever loading are predicted by assigning the element information of the established mesoscale model to the macroscale model. It is shown that the geometric morphology and predicted mechanical responses of the high-fidelity model are consistent with the experimental results. Furthermore, the effect of twist angles on the stiffness properties of the twisted composite structures is analyzed using the presented numerical method. The proposed digital modeling method could provide a guide for the early design of woven composite structures.

具有真实纱线几何形状的中尺度模型可以提高编织复合材料结构性能预测的准确性。本文旨在针对编织复合材料加捻结构提出一种新的中尺度建模方法。首先,利用嵌入基体实体网格中的数字元素纤维高保真地模拟了单元格模型中纱线的扭转变形。然后,结合仿射变换从数字元素变形模型重建扭曲复合结构的实体几何模型。最后,通过将已建立的中尺度模型的元素信息分配到宏观模型中,预测扭曲复合材料结构在悬臂载荷作用下的弹性响应。结果表明,高保真模型的几何形态和预测的力学响应与实验结果一致。此外,还利用所提出的数值方法分析了扭曲角度对扭曲复合材料结构刚度特性的影响。所提出的数字建模方法可为编织复合材料结构的早期设计提供指导。




来源:复合材料力学仿真Composites FEM
ACTMechanicalDeformFidelity复合材料非线性化学航空航天UM理论材料MCAD控制
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首次发布时间:2024-11-06
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【新文速递】2024年2月24日复合材料SCI期刊最新文章

今日更新:Composite Structures 3 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Part B: Engineering 3 篇,Composites Science and Technology 1 篇Composite StructuresSmall-dependent nonlinear analysis of functionally graded triply periodic minimal surface nanoplatesP. Phung-Van, P.T. Hung, Chien H. Thaidoi:10.1016/j.compstruct.2024.117986功能分级三周期最小表面纳米板的小依赖非线性分析This paper introduces an effective and simple approach to analyze functionally graded triply periodic minimal surface (FG-TPMS) nanoplates, taking advantage of a novel nonlocal strain gradient nonlinear analysis. TPMS has recently gained attention as an extraordinary solution for constructing structures, drawing inspiration from natural architectures. It offers remarkable features, including high interconnectivity porous architectures, smooth surfaces, and the ability to achieve mathematically controllable geometry features. However, the extensive potential and benefits of TPMS structures have not been fully explored in current research. Hence, this study aims to address this limitation and unlock new possibilities for FG-TPMS nanoplates. Three patterns of FG-TPMS nanoplates, namely Primitive (P), Gyroid (G), and I-gragh and Wrapped Package-graph (IWP), are utilized in this investigation. The proposed model effectively incorporates the nonlocal,strain gradient and nonlinear effects into nanoplate structures. It enables a comprehensive understanding of the mechanisms responsible for both reducing and enhancing stiffness in the nanoplate by fine-tuning the nonlocal and strain gradient parameters. This research offers promising prospects for future design and optimization, providing a robust approach to address the intricate nonlinear behavior observed in FG-TPMS nanoplates.本文利用新颖的非局部应变梯度非线性分析方法,介绍了一种分析功能分级三周期最小表面(FG-TPMS)纳米板的有效而简单的方法。最近,TPMS 从自然建筑中汲取灵感,作为一种构造结构的非凡解决方案而备受关注。它具有显著的特点,包括高互联性多孔结构、光滑表面以及实现数学可控几何特征的能力。然而,目前的研究尚未充分挖掘 TPMS 结构的广泛潜力和优势。因此,本研究旨在解决这一局限性,为 FG-TPMS 纳米板开启新的可能性。本研究采用了三种 FG-TPMS 纳米板的模式,即原始(P)、陀螺(G)和 I-gragh and Wrapped Package-graph (IWP)。所提出的模型有效地将非局部、应变梯度和非线性效应纳入了纳米板结构。通过微调非局部和应变梯度参数,该模型能够全面了解降低和增强纳米板刚度的机制。这项研究为未来的设计和优化提供了广阔的前景,为解决在 FG-TPMS 纳米板中观察到的错综复杂的非线性行为提供了可靠的方法。Fiber-level modeling of 3D braided preforms using virtual braiding methodXi Liao, Yanan Jiao, Junbo Xie, Li Chendoi:10.1016/j.compstruct.2024.117988利用虚拟编织法进行三维编织预成型的纤维级建模High fidelity geometry models of the preforms are essential in mechanical property analysis for composite materials. The paper presents a virtual braiding method to generate digital material twins of 3D braided preforms. The four-step 3D braiding process is simulated based on the concept of virtual fiber and according to the rule of yarn movement. Fiber-level models of the preform are constructed which display the micro-scale architectures explicitly, including compressive deformations of yarn cross-sections and variations of yarn paths. The Micro-CT test is employed to investigate the internal fiber structures of 3D braided preform and quantitatively verify the accuracy of the proposed modeling method. Influence of the braiding parameters, such as yarn tension and arrangement angle in the initial state on geometric parameters of the preform is then investigated.预型件的高保真几何模型对于复合材料的机械性能分析至关重要。本文介绍了一种虚拟编织方法,用于生成三维编织预型件的数字材料双胞胎。根据虚拟纤维的概念和纱线运动规律,模拟了四步三维编织过程。构建的预型件纤维级模型可清晰显示微尺度结构,包括纱线横截面的压缩变形和纱线路径的变化。利用 Micro-CT 测试研究了三维编织预成型的内部纤维结构,并定量验证了所提出的建模方法的准确性。然后研究了初始状态下纱线张力和排列角度等编织参数对预型件几何参数的影响。Flexural performance of reinforced concrete beams strengthened using near-surface-mounted carbon-fiber-reinforced polymer bars: Effects of bonding patternsJ.B. Lv, D.J. Lin, Bing Fu, S.H. Liu, Z.J. Handoi:10.1016/j.compstruct.2024.117985使用近表面安装的碳纤维增强聚合物条加固的钢筋混凝土梁的挠曲性能:粘结模式的影响The near-surface-mounted (NSM) fiber-reinforced polymer (FRP) technique is effective for enhancing the load carrying capacity of strengthened reinforced concrete (RC) beams. However, this technique significantly reduces the deformability of strengthened RC beams. To overcome this, the present study combines the NSM strengthening method with the partial bonding technique: the strengthening FRP reinforcement is partially bonded onto the concrete substrate). Six full-scale 4.3 m long RC beams strengthened with NSM FRPs using various bonding patterns were tested. The results indicated that mechanical interlocking grooves slightly improve the load carrying capacity, but have a negligible effect on the deformability of the strengthened beams. A decrease in the bond length increased deformability by 27.2 %, with only a 7.6 % drop in load capacity compared to that of the beam with full bonding. An advanced finite element model was developed and validated to confirm an optimal bond length of 930 mm for maximum flexural performance.近表面安装(NSM)纤维增强聚合物(FRP)技术可有效提高加固钢筋混凝土(RC)梁的承载能力。然而,这种技术大大降低了加固后 RC 梁的变形能力。为了克服这一问题,本研究将 NSM 加固方法与部分粘结技术相结合:将加固 FRP 钢筋部分粘结在混凝土基材上)。采用不同粘结模式的 NSM FRP 加固了六根长 4.3 米的全尺寸 RC 梁,并对其进行了测试。结果表明,机械互锁槽可略微提高承载能力,但对加固梁变形能力的影响微乎其微。与完全粘结的梁相比,粘结长度的减少使变形能力提高了 27.2%,而承载能力仅下降了 7.6%。开发并验证了一种先进的有限元模型,以确认最佳粘接长度为 930 毫米,从而实现最大抗弯性能。Composites Part A: Applied Science and ManufacturingRecycling CF/PEEK offcut waste from laser assisted tape placement: Influence of overlaps and gapsAswani Kumar Bandaru, Thomas Anderson, Paul M. Weaverdoi:10.1016/j.compositesa.2024.108104回收激光辅助胶带贴装产生的 CF/PEEK 废料:重叠和间隙的影响A recycling method for waste CF/PEEK prepreg tapes is proposed that uses offcuts from laser assisted tape placement (LATP) processing, without shredding, grinding or further cutting. Laminates (using the prepreg waste) representing different configurations were manufactured considering overlaps and gaps reflecting observed defects in LATP. Interlaminar shear strengths (ILSS) with 0° fibre (Parallel) and bending strength for 90° fibre (Normal) directions were measured. The parallel samples with 3 mm overlap had the highest ILSS (100.3 MPa) while the 2 mm gapped samples had the lowest ILSS (58.7 MPa). The Normal samples failed at the surface due to matrix-dominated failure providing bending strengths between 44.0 MPa and 82.1 MPa. Failure mechanisms were identified similar to that of non-recycled composites reported in the literature (50–120 MPa), indicating that the recycled prepreg tapes retained approximately 84 % of the ILSS of the highest reported values.本文提出了一种废 CF/PEEK 预浸料带的回收方法,该方法使用激光辅助贴带 (LATP) 加工过程中产生的边角料,无需粉碎、研磨或进一步切割。考虑到反映 LATP 中观察到的缺陷的重叠和间隙,制造了代表不同结构的层压板(使用预浸料废料)。测量了 0° 纤维方向(平行)的层间剪切强度(ILSS)和 90° 纤维方向(正常)的弯曲强度。重叠 3 毫米的平行样品的层间剪切强度最高(100.3 兆帕),而间隙为 2 毫米的样品的层间剪切强度最低(58.7 兆帕)。正常样品由于基质主导的失效而在表面失效,弯曲强度介于 44.0 兆帕和 82.1 兆帕之间。失效机制与文献报道的非回收复合材料的失效机制(50-120 兆帕)相似,表明回收预浸带保留了最高报道值约 84% 的 ILSS。Mechanical and interfacial analysis of 3D-printed two-matrix continuous carbon fibre composites for enhanced structural performanceFei Liu, Shenru Wang, Wuxiang Zhang, Xilun Ding, Eleonora Ferraris, Jan Ivensdoi:10.1016/j.compositesa.2024.108105增强结构性能的 3D 打印双基质连续碳纤维复合材料的力学和界面分析Two-matrix continuous carbon fibre composites are recognized for enhancing structural and mechanical properties. However, a comprehensive investigation into their interfacial behaviour and potential has yet to be undertaken. Based on the 3D printing process, this study uses experimental and simulation techniques to analyse the mechanical and interfacial performance across multiple scales. The flexure properties under different processing parameters are studied at the macro level. Meso and micro-structural characterization are evaluated by scanning electron microscopy, optical microscopy and molecular dynamics simulation. The disparities in simulations and experimental results are attributed to macroscopic defects and reinforcement volume fraction. This yields insights into strategies for optimising performance, culminating in a comprehensive understanding of the fracture mechanism of two-matrix continuous carbon fibre composites. Our study provides an approach to creating and analysing other systems with multiple matrix composites and enabling new engineering applications for composites.双基体连续碳纤维复合材料被认为可以提高结构和机械性能。然而,对其界面行为和潜力的全面研究尚未开展。本研究以三维打印工艺为基础,采用实验和模拟技术分析了多种尺度的机械和界面性能。从宏观层面研究了不同加工参数下的挠曲性能。通过扫描电子显微镜、光学显微镜和分子动力学模拟评估了中观和微观结构特征。模拟和实验结果的差异归因于宏观缺陷和增强体体积分数。这使我们对优化性能的策略有了深入的了解,最终对双基体连续碳纤维复合材料的断裂机制有了全面的认识。我们的研究为创建和分析其他多基体复合材料系统提供了一种方法,并使复合材料的新工程应用成为可能。Composites Part B: EngineeringFibre orientation distribution function mapping for short fibre polymer composite components from low resolution/large volume X-ray computed tomographyRobert M. Auenhammer, Anuj Prajapati, Kaldon Kalasho, Lars P. Mikkelsen, Philip J. Withers, Leif E. Asp, Renaud Gutkindoi:10.1016/j.compositesb.2024.111313通过低分辨率/大容积 X 射线计算机断层扫描绘制短纤维聚合物复合材料的纤维取向分布函数图Short glass fibre injection moulded composites, used in interior and exterior automotive parts, are exposed to complex stress states, for example during a crash. As the fibre scale dominates the composite’s material properties, numerical models need to account for the local fibre orientation. In recent years, mould flow simulation results have been exploited to predict the fibre orientations for finite element models, albeit with limited accuracy. Alternatively, X-ray computed tomography can be used to directly image and analyse fibre orientations. Traditionally, achieving the necessary resolution to image individual fibres restricts the imaging to small regions of the component. However, this study takes advantage of recent advancements in imaging and image analysis to overcome this limitation. As a result, it introduces, for the first time, a reliable, fast, and automated fibre orientation mapping for a full component based on image analysis on a single fibre level; even for cases where the pixel size is significantly larger than the fibre diameter. By scanning at lower resolutions, a drastically larger volume of interest can be achieve. The resulting fibre orientation analysis and mapping algorithm, based on X-ray computed tomography, is well matched to the level of information required for automotive crash modelling with a standard element-size of a few millimetres. The entire process, encompassing image acquisition, image analysis and fibre orientation mapping, can be directly integrated in an industrial full component application in a matter of hours.用于汽车内外饰件的短玻璃纤维注塑复合材料会面临复杂的应力状态,例如在碰撞过程中。由于纤维尺度主导着复合材料的材料特性,因此数值模型需要考虑局部纤维取向。近年来,人们利用模流模拟结果来预测有限元模型的纤维取向,尽管精确度有限。另外,X 射线计算机断层扫描也可用于直接成像和分析纤维取向。传统上,要达到成像单个纤维所需的分辨率,成像范围只能局限于部件的小区域。然而,本研究利用成像和图像分析领域的最新进展来克服这一限制。因此,该研究首次在单根纤维层面的图像分析基础上,为整个组件引入了可靠、快速和自动化的纤维方向映射;即使在像素尺寸明显大于纤维直径的情况下也是如此。通过低分辨率扫描,可以获得更大的感兴趣体积。由此产生的基于 X 射线计算机断层扫描的纤维方向分析和绘图算法,完全符合汽车碰撞建模所需的信息水平,其标准元素尺寸仅为几毫米。整个过程包括图像采集、图像分析和纤维取向绘图,可在数小时内直接集成到工业全部件应用中。Architected flexible syntactic foams: Additive manufacturing and reinforcing particle driven matrix segregationHridyesh Tewani, Megan Hinaus, Mayukh Talukdar, Hiroki Sone, Pavana Prabhakardoi:10.1016/j.compositesb.2024.111315结构化柔性合成泡沫:增材制造和增强粒子驱动的基质分离Polymer syntactic foams are transforming materials that will shape the future of next-generation aerospace and marine structures. When manufactured using traditional processes, like compression molding, syntactic foams consist of a solid continuous polymer matrix reinforced with stiff hollow particles. However, polymer matrix segregation can be achieved during the selective laser sintering process with thermoplastic polyurethane (TPU). It is uncertain what role hollow particles play in forming this matrix segregation and its impact on the corresponding mechanical properties of syntactic foams. We show that the size of the hollow particles controls the internal microscale morphology of matrix segregation, leading to counter-intuitive macroscale mechanical responses. Particles with diameters greater than the gaps between the cell walls of the segregated matrix get lodged between and in the walls, bridging the gaps in the segregated matrix and increasing the stiffness of syntactic foams. In contrast, particles with smaller diameters with higher particle crushing strength get lodged only inside the cell walls of the segregated matrix, resulting in higher densification stresses (energy absorption). We show that stiffness and densification can be tuned while enabling lightweight syntactic foams. These novel discoveries will aid in facilitating functional and lightweight syntactic foams for cores in sandwich structures.聚合物合成泡沫是一种变革性材料,它将塑造下一代航空航天和海洋结构的未来。在使用压缩成型等传统工艺制造时,合成泡沫由固态连续聚合物基体和硬质空心颗粒组成。然而,在热塑性聚氨酯(TPU)的选择性激光烧结过程中,聚合物基质会发生偏析。目前还不确定空心颗粒在形成这种基质偏析中起到什么作用,以及它对合成泡沫相应机械性能的影响。我们的研究表明,中空颗粒的大小控制着基质离析的内部微观形态,从而导致与直觉相反的宏观机械响应。直径大于离析基质细胞壁间隙的颗粒会嵌入细胞壁之间和细胞壁内,从而弥合离析基质的间隙,增加合成泡沫的刚度。相反,直径较小、颗粒破碎强度较高的颗粒只能嵌入离析基质的细胞壁内,从而导致较高的致密化应力(能量吸收)。我们的研究表明,在实现轻质合成泡沫的同时,还可以调整刚度和致密性。这些新发现将有助于促进功能性轻质合成泡沫在夹层结构中的核心应用。A Novel machine learning model to design historical-independent health indicators for composite structuresMorteza Moradi, Ferda C. Gul, Dimitrios Zarouchasdoi:10.1016/j.compositesb.2024.111328 设计与历史无关的复合材料结构健康指标的新型机器学习模型Developing comprehensive health indicators (HIs) for composite structures encompassing various damage types is challenging due to the stochastic nature of damage accumulation and uncertain events (like impact) during operation. This complexity is amplified when striving for HIs independent of historical data. This paper introduces an AI-driven approach, the Hilbert transform-convolutional neural network under a semi-supervised learning paradigm, to designing reliable HIs (fulfilling requirements, referred to as 'fitness'). It exclusively utilizes current guided wave data, eliminating the need for historical information. Ensemble learning techniques were also used to enhance HI quality while reducing deep learning randomness. The fitness equation is refined for dependable comparisons and practicality. The methodology is validated through investigations on T-single stiffener CFRP panels under compression-fatigue and dogbone CFRP specimens under tension-fatigue loadings, showing high performance of up to 93% and 81%, respectively, in prognostic criteria.由于损伤累积的随机性和运行期间的不确定事件(如撞击),为包含各种损伤类型的复合材料结构制定全面的健康指标(HIs)具有挑战性。在寻求独立于历史数据的健康指标时,这种复杂性会进一步放大。本文介绍了一种人工智能驱动的方法,即半监督学习范式下的希尔伯特变换-卷积神经网络,用于设计可靠的 HI(满足要求,称为 "适配性")。它完全利用当前的导波数据,无需历史信息。此外,还使用了集 合学习技术来提高 HI 质量,同时减少深度学习的随机性。为了实现可靠的比较和实用性,对适度方程进行了改进。通过对压缩疲劳下的 T 型单加强筋 CFRP 面板和拉伸疲劳载荷下的狗骨 CFRP 试样进行研究,验证了该方法,结果表明其在预后标准方面的性能分别高达 93% 和 81%。Composites Science and TechnologyA novel one-step eco-friendly dipping system for PA66 fiber/rubber composites with excellent interfacial adhesion and its adhesion mechanismChaojun Wang, Xuewen Cheng, Wei Huang, Bing Yu, Nanying Ning, Ming Tiandoi:10.1016/j.compscitech.2024.110513 具有优异界面粘附力的 PA66 纤维/橡胶复合材料的新型一步法环保浸渍系统及其粘附机理Fiber-reinforced rubber composites (FRRC) are widely used in tires, hoses, conveyor belts and other fields. Currently, the industry heavily relies on the resorcinol-formaldehyde-latex (RFL) system to enhance interfacial adhesion performance of FRRC; however, both resorcinol (R) and formaldehyde (F) pose significant risks to human health and the environment. Thus, some two-step RF-free dipping systems have been developed to replace RFL system. Nevertheless, these complex two-step systems face challenges during industrialization. In this study, we proposed a novel one-step eco-friendly dipping system (PCGL) for PA66 fibers. By using the new system, a solid transition bridge between PA66 fiber and rubber matrix can be formed, due to the bonding between PA66 and isocyanate, the interaction among polyacrylic acid resin, isocyanate and epoxy, the catalytic effect of triethanolamine, as well as the co-crosslinking of styrene-butadiene-vinyl-pyridine latex and rubber. The interfacial adhesion performance of PA66 fiber/rubber composites treated by PCGL with optimized ratio of epoxy groups/isocyanate groups can reach more than 90% of RFL level, meeting industry requirements for high interfacial bonding performance, while maintaining strength and safety of composites. The mechanism of largely enhanced interfacial adhesion was revealed through the analysis of modulus transition and co-crosslinking at the composite interface.纤维增强橡胶复合材料(FRRC)广泛应用于轮胎、软管、传送带等领域。目前,该行业主要依赖间苯二酚-甲醛-乳胶(RFL)系统来提高 FRRC 的界面粘合性能;然而,间苯二酚(R)和甲醛(F)都会对人类健康和环境造成严重危害。因此,人们开发了一些两步无射频浸渍系统来取代 RFL 系统。然而,这些复杂的两步法系统在工业化过程中面临着挑战。在本研究中,我们针对 PA66 纤维提出了一种新型的一步法环保浸渍系统(PCGL)。通过使用这种新体系,PA66 纤维与橡胶基体之间可以形成固体过渡桥,这是由于 PA66 与异氰酸酯之间的粘合作用,聚丙烯酸树脂、异氰酸酯和环氧树脂之间的相互作用,三乙醇胺的催化作用,以及苯乙烯-丁二烯-乙烯基吡啶胶乳与橡胶的共交联作用。环氧基团/异氰酸酯基团比例优化的 PCGL 处理的 PA66 纤维/橡胶复合材料的界面粘合性能可达 RFL 水平的 90% 以上,满足了行业对高界面粘合性能的要求,同时保持了复合材料的强度和安全性。通过分析复合材料界面的模量转变和共交联,揭示了界面粘合力大幅增强的机理。来源:复合材料力学仿真Composites FEM

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