Fiber breakage and waviness defects are two significant and inevitable defects existing in three-dimensional braided composites (3DBCs). This work proposed a new method to create the numerical model containing fiber breakage and waviness defects at the micro-scale level according to experimental characterization results. The experimental tests of 3DBCs with various braiding angles and matrix types are then designed to verify the reliability and adaptability of the model. The results indicate that the fiber breakage and waviness defects both gave rise to an apparent decrease in the axial mechanical properties of the unidirectional and braided composites. The influences of two kinds of defects on 3DBCs are also related to the braiding angles. In addition, the effect of matrix type on the 3DBC is apparent that should not be neglected. The primary reasons of the change of compressive properties of 3DBCs with different matrix types are the variations of the matrix and interfacial properties. The proposed modeling method in this work can be extended for those composites that include a large quantity of fiber breakage and waviness defects.
Numerical analysis of L-shaped wrinkling behavior of 3D woven preforms based on a novel hybrid element yarn model
Zhi Yang, Lin Shi, Yanan Jiao, Junbo Xie, Xiaoying Cheng, Zhenyu Wu, Qingqing Ni
doi:10.1016/j.compstruct.2024.118207
基于新型混合单元纱线模型的三维机织预制件l形起皱行为数值分析
Numerical simulation is a key means to evaluate the forming performance of 3D woven preforms (3DWPs). However, the macroscopic continuous model of 3DWPs cannot predict the orientation and deformation of yarns, while the microscopic discrete model is unsuitable for large-size samples forming simulation due to computational constraints. A novel mesoscopic hybrid element yarn model is thus proposed to establish a large-size 3D woven virtual yarn preform (VYP) model and the L-shaped virtual forming simulation model. The L-shaped forming experiment of the 3DWP is designed and executed, and the accuracy of the numerical simulation models is verified from three aspects: the mechanical curve, the sample's macroscopic morphology, and the local meso-structure features. Subsequently, the deformation behavior of the yarn structure inside the 3DWP during the L-shaped forming process is analyzed by combining experimental and simulation results. Furthermore, the effects of the L-shaped angle and chamfer radius on the deformation behavior of the 3DWP are studied, which helps guide the structural design of 3DWPs.
Composites Part A: Applied Science and Manufacturing
Progressive damage modeling in open hole composite laminates with ultrasound-informed drilling-induced delamination
Kirtunia Rahul, Arief Yudhanto, Pruthul Kokkada Ravindranath, David A. Jack
doi:10.1016/j.compositesa.2024.108262
超声诱导钻井分层的裸眼复合材料层合板的渐进损伤建模
Insertion of fasteners, often used in aerospace and automotive industries, requires drilling that induces non-uniform delamination between lamina of a carbon fiber reinforced plastic (CFRP). Understanding the effect of drilling-induced delamination on the mechanical performance and associated damage mechanisms (progressive damage and failure) is critical to ensure joining integrity. The present work develops an ultrasound testing (UT) method to quantify the drilling-induced delamination at each individual ply interface for CFRP laminates. We then develop a mesoscale finite element (FE) model of an open hole tension specimen by incorporating the UT-obtained drilling-induced delamination at each interface. This delamination is modeled using cohesive zone elements with a bilinear traction-separation law with progressive damage in each ply modeled using the 3D Hashin along with a progressive damage model. Our FE model, with UT-informed delamination, accurately predicts experimental observations of the stress concentration around the hole, damage progression, and open hole tension strength.
Pioneering the Carbon Fiber Frontier: A Half-Century of Industry Leadership and the Road Ahead
Fumihiko Tanaka
doi:10.1016/j.compositesb.2024.111515
开拓碳纤维前沿:半个世纪的行业领先地位和未来之路
Polyacrylonitrile (PAN)-based carbon fibers have been in full-scale industrialization for more than 50 years, during which time it has grown at an annual rate of 10-20% for half a century, a trend that is expected to continue. Throughout this period, the carbon fiber industry has supported the composites industry through a stable global supply and improved fiber quality. Here, we show PAN-based carbon fibers’ history and future for this 50-year milestone. The industrialization of carbon fiber began in 1959, when Shindo discovered how to stabilize PAN. The later discovery of comonomers based on the Morita-Baylis-Hilman reaction by Morita in 1966 further enabled industrialization. In addition to the innovativeness of this breakthrough, progress was made in converging technologies which intensified competition and encouraged incremental innovation. In recent years, microstructure control has become increasingly precise: down to the molecular level through incremental innovations, with tensile strength reaching 8.0 GPa and named T1200. Evaluating the carbon fibers’ intrinsic strength by the loop method, where evaluation size is reduced to the order of tens of micrometers, shows that the maximum value of T1200 is very high at 18 GPa. This is almost consistent with the value of 19 GPa predicted using molecular dynamics. Even higher strength can be expected by reducing defects. These performance improvements have already contributed toward carbon neutrality in aircraft and wind power generation. PAN-based carbon fibers will continue to be an important material in the future as further performance improvements and increased mass production are realized.
Thermomechanical fatigue behavior of CF/PEKK composite under low and ultrasonic frequencies
Jafar Amraei, Tomasz Rogala, Andrzej Katunin, Aravind Premanand, Grzegorz Kokot, Dominik Wachla, Wacław Kuś, Marcin Bilewicz, Bilal Khatri, Frank Balle
doi:10.1016/j.compositesb.2024.111539
CF/PEKK复合材料在低频和超声下的热疲劳行为
This study aimed to extract the thermomechanical fatigue behavior of a CF/PEKK composite under low and ultrasonic frequency fatigue tests (LFFTs and UFFTs) in the presence of the self-heating effect. Preliminary increasing amplitude tests (IATs) were performed to obtain the minimum load level at which the self-heating is observable. Extracting the fatigue strength from T-σ curves for three mean stress levels resulted in constructing S-N curves for the LFFT regime at different load levels using a shift procedure. However, combining LFFT and UFFT results via S-N curve was impractical, while joining such results through the heat dissipation rate (q) was feasible for various constant amplitude tests and IATs. The derived σ-q curves from combining LFFT and UFFT results and comparing the fracture mechanisms of CF/PEKK composite using fractography would make a step for bridging the transition zone between LFFTs and UFFTs and making the results transferable. The microscopy images obtained from fractography also confirmed the similarities of fatigue fracture mechanisms between LFFTs and UFFTs.
Enhanced thermal conductivity and mechanical property via improvement of hydrogen bonding between hexagonal boron nitride and aramid copolymer
Hwakyung Jeong, Jaegeun Lyu, Howon Choi, Min Woo Kim, Juyoung Kim, Hyeonsuk Yoo, Yongjin Lee, Ji Ho Youk, Han Gi Chae
doi:10.1016/j.compscitech.2024.110652
通过改善六方氮化硼与芳纶共聚物之间的氢键，提高了其导热性和力学性能
This study focuses on enhancing thermal properties of aramid copolymer nanocomposites by integrating hexagonal boron nitride (hBN). Pristine hBN (P-hBN) is first subjected to oxidative heat treatment at 900 °C, producing thermally treated hBN (T-hBN), which significantly improves thermal conductivity while also increasing the tensile properties of composites. The study further explores the effect of different diamine co-monomers, 3,4’- and 4,4’-oxydianiline (ODA), on the nanocomposite properties. Both types of ODA-based composite films show improvement in various properties containing T-hBN. With 20 wt% of T-hBN, the 3,4'-ODA and 4,4'-ODA-based films exhibit 33.2% and 290% increase in tensile strength and thermal conductivity, respectively. The functionalization of hBN by heat treatment enhances the interaction between aramid copolymer and hBN and prevents the aggregation of hBN. The rough interface was shown in fractured images for films with T-hBN, suggesting that the composite films with T-hBN withstand higher external forces. In addition, it was observed that T-hBN exhibits better dispersion compared to P-hBN. This is supported by molecular dynamics (MD) simulation, and, in addition, it also provides the underlying mechanism for the property differences between both types of co-monomers.
Enhanced interfacial, mechanical, and anti-hygrothermal properties of carbon fiber/cyanate ester composites with the catalytic sizing agents of titanium epoxy
The mechanical properties of composites are closely related to the interfacial behavior, especially under the hygrothermal circumstance. A catalytic sizing agent of titanium epoxy is designed to enhance interfacial, mechanical, and anti-hygrothermal properties of high modulus carbon fiber (HMCF)/cyanate ester composites simultaneously. The mechanisms of interface enhancement and low hygroscopicity of composites are investigated. The titanium epoxy is synthesized and its catalytic effect on the curing of cyanate ester is proved. The interfacial properties of HMCF composites with catalytic sizing agents are improved to 95.5 MPa, which is attributed to the interphase with high crosslinking density and sufficient triazine rings and oxazolidinone structure due to preferential curing induced by interfacial catalysis, stimulating the smooth transition of interphase modulus. Further, the formed interphase exhibits few interface defects and low content of hydroxyl groups, which changes the moisture diffusion path and reduces saturated water absorption of composites to only 0.36%, resulting in the release of interfacial wet stress concentration and high retention of mechanical properties in hygrothermal environment. The resultant composites with high stiffness, excellent temperature resistance, superior dimensional stability and low moisture absorption are expected to be applied to high-orbit space, aerospace, precision instruments.
Poor adhesion between silver nanomaterials and substrates seriously restricts the development of electronic composite devices. In this work, flexible and conductive silver nanowires/fibroin/ degummed silk (AgNWs/fibroin/dSF) composite fibers with high adhesion and conductivity via capillarity-assisted assembly for electromagnetic interference (EMI) shielding are designed and fabricated by a facile and scalable all-solution dip-coating method. The nanocomposite fiber possesses high conductivity with a resistance of 8.8 Ω/cm at a low AgNWs/fibroin loading of 19.3 wt%. The assistance of the capillary force in the fiber highly increases the mass of deposited AgNWs. Furthermore, the AgNWs show high adhesion on the fibers in the tape-peel test. The enhanced deposition factors and mechanisms are detailly investigated. Moreover, the composite fibers are further woven into a soft and flexible fabric. The composite fabric shows an absorption-dominated EMI shielding performance with an efficient shielding effectiveness of 38 dB. The capillarity-assisted assembly is an attractive procedure for constructing high-conductive and uniform coatings for a wide application.
Enhanced thermoelectric properties of carbon nanotubes/polyaniline fibers through engineering doping level and orientation
Chun Zhang, Yalong Liu, Hui Li, Siqi Liu, Pengcheng Li, Han Zhang, Chaobin He
doi:10.1016/j.compscitech.2024.110660
通过工程掺杂水平和取向增强碳纳米管/聚苯胺纤维的热电性能
The rapid progress of miniaturized wearable electronics has put forward great requirements for organic fiber-based thermoelectric (TE) generators. Despite polyaniline (PANI) exhibits many outstanding attributes such as facile synthesis and low cost, as well as good environmental and thermal stability, only a few PANI-based fibers were fabricated and their TE efficiency needs to be further improved. In this work, the TE performance of wet-spun carbon nanotubes (CNTs)/PANI fibers was improved by synergistic engineering doping level of PANI and orientation of the fibers. The doping degree was optimized by varying coagulation baths, bath durations, and dopant loadings in the spinning solution, followed by fixing process during air drying to decrease shrinkage and enhance orientation of the fiber. Hexane coagulated CNTs/PANI fibers exhibited a higher doping degree of PANI compared to that of acetone and ethyl acetate, resulting in a maximum TE power factor of 77.4 μW m-1K-2 for 71 wt% CNTs/PANI fibers at PANI/dopant molar ratio of 2:1.25. Further fixing process induced a more oriented structure along the fibers, facilitating carrier transport and contributing to a significantly increased conductivity of 2155 S cm-1. Consequently, the CNTs/PANI fibers reached an optimal power factor of 91.8 μW m-1K-2. With outstanding TE performance and mechanical properties, the resultant fibers were assembled to fabricate a flexible TE generator, which generated a high output power of 2.5 nW with a temperature gradient of 10 K. These results demonstrate the potential of high-performance CNTs/PANI fibers to harvest body heat for the power supply of the wearable electronics.
小型化可穿戴电子产品的快速发展对有机纤维热电发生器提出了很高的要求。尽管聚苯胺(PANI)具有合成简单、成本低、环境和热稳定性好的优点，但目前制备的聚苯胺基纤维数量较少，其TE效率有待进一步提高。本研究通过聚苯胺的工程掺杂水平和纤维取向的协同作用，提高了湿纺碳纳米管/聚苯胺纤维的TE性能。通过改变混凝浴、浴浴时间和纺丝液中掺杂量来优化掺杂程度，然后在风干过程中进行固定工艺，以减少收缩，增强纤维的取向性。与丙酮和乙酸乙酯相比，己烷混凝的CNTs/PANI纤维具有更高的PANI掺杂度，当PANI/掺杂摩尔比为2:25时，71% wt%的CNTs/PANI纤维的最大TE功率因数为77.4 μW m-1K-2。进一步的固定过程诱导了沿纤维方向更定向的结构，促进了载流子的运输，并显著提高了2155 S cm-1的电导率。因此，CNTs/PANI纤维的最佳功率因数为91.8 μW m-1K-2。合成的纤维具有优异的TE性能和机械性能，组装成柔性TE发生器，产生2.5 nW的高输出功率，温度梯度为10 K。这些结果表明，高性能碳纳米管/聚苯胺纤维有潜力收集人体热量，为可穿戴电子设备供电。
