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 2 篇
Composite Structures
Numerical modeling thermo-hygro-mechanical coupling of cross-ply laminate composites using a nonlocal discrete approach
Liu Donglai, Chen Hailong
doi:10.1016/j.compstruct.2023.117618
采用非局部离散方法对交叉层压复合材料的热-湿-机械耦合进行数值建模
Laminate composites are widely used in various industrial applications and are frequently subject to extreme temperature and moisture environment. This paper presents numerical modeling thermo-hygro-mechanical coupling of cross-ply laminate composites using a nonlocal discrete approach formulated based on the local continuum mechanics theory. In the developed model, the material domain is modeled as an assembly of regularly packed material particles whose interaction with neighboring material particles via bonds is nonlocal. Bond parameters are derived based on equivalency of energy and diffusing material transfer rate between the discrete descriptions and their continuum counterparts. The orthotropy of material properties is modeled using rotation of discretization lattice rather than the coordinate transformation that used in the local continuum mechanics theory. The interface and its effect on the material response is investigated by assigning different parameters to bond straddling different material phases. Numerical verification using single and four-ply laminate composites shows excellent accuracy of the developed model.
The effect of the crystalline structure of polyamide 6 (PA6) among carbon fiber (CF) on the mechanical properties of PA6/CF composites was explored using two types of PA6 with different spherulite sizes. Infrared (IR) spectroscopy showed that intra/intermolecular interactions were nearly equivalent for the two types of PA6. The viscoelasticities in the molten state were almost identical; that is, the molecular weights of the PA6s were comparable. The mechanical properties of the PA6 matrix with smaller spherulites (PA6a) in PA6/CF were superior to those of the PA6 matrix with larger spherulites (PA6b). Polarized light microscopy, wide-angle X-ray scattering, and polarized Raman spectroscopy revealed oriented crystals of PA6a in the PA6a/CF composite and random crystals of PA6b in the PA6b/CF composite. Therefore, the superior mechanical properties of PA6/CF are due to the oriented crystal chains of PA6, which support the overall stress transfer in composites.
A meso-scale stochastic model for tensile behavior of 2D woven ceramic composites considering void defects and stacking mode
Li Yihang, Ma Yong, Guan Tianhao, Wang Zhen, Zhang Chao, Suo Tao
doi:10.1016/j.compositesa.2023.107838
考虑空隙缺陷和堆叠模式的二维编织陶瓷复合材料拉伸行为中尺度随机模型
A sophisticated meso-scale model is developed based on finite element method to study the tensile failure behavior of 2D-SiCf/SiC. To this end, a thoroughgoing characterization was carried out using SEM and micro-CT to obtain the microstructural parameters, and a progressive damage model related to matrix cracking was proposed for fiber tows to depict the matrix brittleness, an essential feature of ceramic matrix composites. Thereby, a sophisticated model comprehensively incorporating void defects, layer shifts and the damage induced by matrix cracking was established. Elaborate experimental tests including digital image correlation, acoustic emission (AE) and high-speed observation were synthetically conducted to validate this model, and results indicated that this model could provide an accurate prediction. Especially, micro and meso-scale damage modes were identified and the damage process was thoroughly analyzed by combing this model and AE technology. The numerical studies were then implemented to evaluate the effect of stacking mode and porosity.
Exploring the piezoresistive sensing behaviour of ultra-high performance concrete: Strategies for multiphase and multiscale functional additives and influence of electrical percolation
Song Facheng, Chen Qing, Zhang Mingzhong, Jiang Zhengwu, Ding Wenqi, Yan Zhiguo, Zhu Hehua
doi:10.1016/j.compositesb.2023.111042
探索超高性能混凝土的压阻传感行为:多相和多尺度功能添加剂的策略以及电渗流的影响
Self-sensing ultra-high performance concrete (UHPC) features superior mechanical capacity, excellent erosion resistance, long life cycle, and broad range of stress sensing, and is expected to be a pathway towards next-generation smart cementitious composites. This study presents a novel strategy to achieve electrical percolation and elevate the piezoresistive sensing capability of UHPC through the incorporation of multiphase and multiscale functional additives including graphene (G) and carbon nanotube (CNT). The workability, compressive strength, microstructural characteristics, and alternating current (AC) impedance response are investigated. The effect of electrical percolation on the piezoresistive behaviour is studied and discussed using various ratios of G/CNT. Results indicate that as the G/CNT ratio decreases from 4:0 to 0:4, the compressive strength is reduced from 194.7 MPa to 166.3 MPa due to the certain increase in the plastic viscosity of fresh mixture and the proportion of harmful pores, although the basic requirement of 150 MPa is met. Moreover, the AC impedance response significantly moves left and the radius of high-frequency arc reduces from 72910 Ω to 1295 Ω, suggesting electrical percolation. Bounded by percolation threshold, the fractional change of resistance curves can be divided into a two-stage pattern (i.e., linear and nonlinear stages) and a three-stage mode (i.e., linear decrease, balance, and abrupt increase stages). An underlying mechanism is proposed to explain the tremendous change in piezoresistive behaviour of self-sensing UHPC, considering the tunneling-percolation theory and electromechanical coupling behaviour. Additionally, the gauge factors range from 11 to 28, which is higher than most of the existing reported values, demonstrating the great potential of using hybrid functional nano-additives in self-sensing UHPC.
Nanofibrillar self-reinforced cyclic olefin copolymer composite foam with high toughness and thermal insulation
Kim Eric S., Lu Miao, Zhang Ruiyan, Lee Patrick C.
doi:10.1016/j.compscitech.2023.110306
具有高韧性和隔热性能的纳米纤维自增强环烯烃共聚物复合泡沫塑料
Thermally insulating and sustainable polyolefin foams play an important role in alleviating heat waste. Cyclic olefin copolymer (COC) has remarkable heat resistance and low thermal conductivity, which makes it an excellent candidate as a thermal insulative material. However, COC has critical drawbacks in its foam processing due to low melt strength, which limits its effective application as a thermal insulative material. Herein, we exploit nanofibrillar processing technology to enhance melt strength to develop highly tough and thermally insulating self-reinforced COC composites. The nanofibril network generated by drawing from the COC blends provides dramatic enhancements in the mechanical, rheological and final foam and thermal insulation properties. In particular, this process increases tensile toughness of COC composites by up to twenty-folds higher than neat COC. The results of foam process reveal the presence of COC fibrils in COC matrix improved volume expansion ratio as well as the cell density of the COC composites. Specifically, the expansion ratio of the foams reaches up to 11 with a cell density of 107 cell/cm3, two orders of magnitude higher than that of neat COC foams and thermal conductivity decreased from 0.062 to 0.033 W m−1K−1. As a proof of concept, this work provides a new insight of a self-reinforced approach to develop recyclable, highly tough, and thermally insulative foam.
The fibre kinking fracture toughness of laminated composites under combined compression and shear
He Rui, Cheng Longfei, Gao Yidi, Cui Hao, Li Yulong
doi:10.1016/j.compscitech.2023.110307
层压复合材料在压缩和剪切联合作用下的纤维扭结断裂韧性
Compact compression specimens with off-axis fibres are employed in this paper, to investigate the effect of in-plane shear stress on the fibre kinking compressive fracture toughness of laminates. The strain distribution on the surface of the specimen was analysed using the digital image correlation method, and the damage process was monitored with thermal imaging. It was noted that the in-plane shear stress introduced by off-axis angle fibres caused an increase in the values of the R-curves when the off-axis angle was 10° or more. The microscopic morphology reveals that as the off-axis angle of the fibres increases, there is an increasing splitting of large fibre bundles, followed by the fibre compression failure within these bundles. This multi-step damage process may be responsible for the increase in energy dissipation.
本文采用了带有离轴纤维的紧凑压缩试样,以研究面内剪应力对层压板纤维扭结压缩断裂韧性的影响。采用数字图像相关方法分析了试样表面的应变分布,并利用热成像技术监测了破坏过程。结果表明,当偏离轴角为 10° 或更大时,偏离轴角纤维引入的面内剪应力会导致 R 曲线值增加。微观形态显示,随着纤维偏离轴心的角度增大,大纤维束的劈裂越来越多,随后这些纤维束内的纤维压缩失效。这种多步骤破坏过程可能是能量耗散增加的原因。