今日更新:Composite Structures 3 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Science and Technology 2 篇
Fatigue life improvement mechanisms of CFRP/Al hybrid joints – Load sharing study using a digital image correlation technique
He Zongkai, Zheng Gang, Luo Quantian, Li Qing, Sun Guangyong
doi:10.1016/j.compstruct.2023.117625
CFRP/Al复合接头疲劳寿命提高机理——基于数字图像相关技术的载荷分担研究
In comparison with an adhesive joint, a hybrid joint often provides a more effective and reliable way to meet heightened safety requirements in engineering like FAA AC 20-107B. Nevertheless, its fatigue failure characterization, life improvement mechanism and engineering design approach have been understudied as compared to the static loading condition. This study aims to characterize the failure mechanisms by use of the digital image correlation (DIC) technique for elucidating the load sharing phenomenon of hybrid joints in the course of fatigue failure. In the study, bonded, riveted and hybrid joints were tested under static and fatigue loading conditions. To explore different mechanical behaviors of hybrid joints, two types of adhesives with an evident difference in modulus were selected to fabricate the joints. The fatigue life of an adhesive layer and that of the hybrid joint were separately studied to explore the means for life improvement. It is shown that the fatigue life of the hybrid joint can be significantly improved as a result of load sharing by rivets. The improvement of the fatigue life could reach 5 to 13 folders for the hybrid joint due to the load sharing, whereas its improvement ratio was only 1 to 2 times when the adhesive and the rivet were independent. By considering the overlap area as an effective region for design of rivet group, an optimal stiffness can be obtained for the hybrid joint. This study clearly presents two completely different fatigue failure processes for hybrid joints and illustrates the improvement mechanisms of fatigue life, thereby providing useful guidance for optimal design of hybrid joints.
与粘合接头相比,混合接头通常提供更有效、更可靠的方式来满足FAA AC 20-107B等工程中更高的安全要求。然而,与静态载荷相比,其疲劳失效特征、寿命提高机制和工程设计方法研究尚不充分。本研究旨在利用数字图像相关(DIC)技术表征混合接头在疲劳破坏过程中的载荷分担现象。在研究中,测试了粘接、铆接和混合连接在静态和疲劳载荷条件下的性能。为了探究混合接头的不同力学行为,选择了两种模量差异明显的胶粘剂进行混合接头的制备。分别对粘接层疲劳寿命和混合接头疲劳寿命进行了研究,探讨了提高粘接层疲劳寿命的方法。结果表明,铆钉的载荷分担可以显著提高混合接头的疲劳寿命。载荷分担可使混合接头的疲劳寿命提高5 ~ 13倍,而胶粘剂和铆钉独立时的疲劳寿命提高率仅为1 ~ 2倍。将重叠区域作为铆钉组设计的有效区域,可获得混合连接的最优刚度。本研究清晰地揭示了混合接头的两种完全不同的疲劳失效过程,阐明了混合接头疲劳寿命的提高机理,为混合接头的优化设计提供了有益的指导。
Impact of parametric variation to achieve extreme mechanical metamaterials through topology optimization
Saurabh Shubham, Gupta Abhinav, Chowdhury Rajib
doi:10.1016/j.compstruct.2023.117611
影响参数变化,通过拓扑优化实现极端力学超材料
Metamaterials are manufactured structures having extreme properties which do not exist in nature. Topology optimization(TO) provides an excellent alternative to the intuition-based homogenization approach used in commercial packages for automating the design of metamaterials. However, multiple topological parameters must be decided to get the tailored effective properties. This research aims to study the optimum parameters to be used in TO for developing incompressible material. To achieve this, we design microstructures to maximize bulk modulus. Various parametric studies are performed by varying topological parameters such as volume fraction, penalization power, filter radius, mesh size and initial design. In addition to this, the combinations of these parameters are also investigated. These studies will be helpful for the design of incompressible metamaterials. The bulk modulus for topologically optimized designs approaches the Hashin–Shtrikman upper bound(HSUB). The results show that appropriate parameter selection can significantly improve the microstructure’s incompressibility. Such materials can have potential applications in designing aerospace and energy-absorbing components.
超材料是具有自然界中不存在的极端特性的人造结构。拓扑优化(TO)为用于超材料自动化设计的商业封装中使用的基于直觉的均质化方法提供了一个极好的替代方案。然而,为了获得定制化的有效性质,必须确定多个拓扑参数。本研究的目的是研究可用于不可压缩材料开发的最佳参数。为了实现这一目标,我们设计微结构以最大化体积模量。通过不同的拓扑参数,如体积分数、惩罚功率、过滤半径、网格尺寸和初始设计,进行各种参数研究。除此之外,还研究了这些参数的组合。这些研究将有助于不可压缩超材料的设计。拓扑优化设计的体积模量接近Hashin-Shtrikman上限(HSUB)。结果表明,适当的参数选择可以显著改善微结构的不可压缩性。这种材料在设计航空航天和吸能部件方面具有潜在的应用前景。
A progressive damage model for carbon fiber-reinforced polymer laminates subjected to fastener pull-through failure
Zhuang Weimin, Zhang Hailun, Wang Enming, Chen Shen, Liu Yang
doi:10.1016/j.compstruct.2023.117623
碳纤维增强聚合物层压板扣件拉穿失效的渐进损伤模型
Most studies on composite joints focus on in-plane bearing mode, while little attention to fastener pull-through failure mode from out-of-plane loads. This paper presents a 3D continuum damage mechanics (CDM) model to investigate and assess the mechanical behaviors of carbon fiber-reinforced polymer (CFRP) laminates subjected to pull-through failure. The proposed model based on the use of intralaminar and interlaminar damage models is established and implemented by means of a user-defined subroutine VUMAT for Abaqus/Explicit. The novelty lies in the material model integrating the thresholds preset by the semianalytical approximation approach, which largely eliminates unnecessary fracture angle enumerations in Puck’s IFF theory, coupled with the simple parabolic interpolation search (SPIS) technique for optimal fracture angle search, considerably reducing the computational burden. Moreover, the numerical results compare well with experiments, effectively replicating the load-displacement response, damage modes, failure behaviors and damaged areas. This study provides an accurate and efficient computational methodology to analyze pull-through failures, enhancing the damage modeling and predictive capabilities for composite joints under out-of-plane loads.
对复合材料接头的研究大多集中在面内承载模式,而对面外载荷作用下紧固件拉穿破坏模式的研究较少。本文提出了一种三维连续损伤力学(CDM)模型,用于研究和评估碳纤维增强聚合物(CFRP)层合板在拉穿破坏下的力学行为。基于层内和层间损伤模型建立了该模型,并利用Abaqus/Explicit的自定义子程序VUMAT实现了该模型。新颖之处在于材料模型集成了由半解析近似方法预设的阈值,这在很大程度上消除了Puck的IFF理论中不必要的断裂角枚举,再加上简单的抛物插值搜索(SPIS)技术进行最佳断裂角搜索,大大减少了计算量。数值结果与实验结果吻合较好,有效地再现了荷载-位移响应、损伤模式、破坏行为和损伤区域。该研究提供了一种准确、高效的计算方法来分析拉穿失效,增强了复合材料接头在面外载荷作用下的损伤建模和预测能力。
Measuring the interlaminar fracture toughness of thin carbon fiber/polyamide6 composites using adhesively bonded stiffeners
Simaafrookhteh Sepehr, Tsokanas Panayiotis, Loutas Theodoros, Lomov Stepan V., Ivens Jan
doi:10.1016/j.compositesa.2023.107841
用粘接增强筋测定薄碳纤维/聚酰胺复合材料的层间断裂韧性
The present work investigates the interlaminar fracture toughness of a thin unidirectional carbon fiber-reinforced/polyamide6 (CF/PA6) composite laminate. Aluminum (Al) stiffening beams are adhesively bonded on both sides of the thin laminate to avoid undesirable large deformations during the subsequent double cantilever beam (DCB) tests. Experimentation with various surface treatment techniques and different adhesives is presented, from which it is concluded that the mode I fracture toughness of the CF/PA6 laminate is always higher than the fracture toughness of the adhesives used in this work. Consequently, the crack initiates at the Al–composite interface. A finite element (FE) model is proposed, and quantitative results for the fracture toughness of the laminate are provided (e.g., GIc,ini= 2.1N/mm). Overall, the study highlights the challenges during the adhesive joining of stiffening beams to CF/PA6 surfaces, ways to improve adhesion, and FE simulation as an alternative to measuring the fracture toughness of such thin laminates.
本研究探讨了单向碳纤维增强/聚酰胺6(CF/PA6)复合材料薄层板的层间断裂韧性。铝(Al)加劲梁被粘合在薄层板的两侧,以避免在随后的双悬臂梁(DCB)试验中出现不希望出现的大变形。实验中使用了各种表面处理技术和不同的粘合剂,由此得出结论:CF/PA6 薄片的模式 I 断裂韧度总是高于本实验中使用的粘合剂的断裂韧度。因此,裂纹起始于铝-复合材料界面。我们提出了一个有限元(FE)模型,并提供了层压板断裂韧性的定量结果(如 GIc,ini= 2.1N/mm)。 总之,该研究强调了加劲梁与 CF/PA6 表面粘接过程中的挑战、改善粘接的方法以及 FE 模拟作为测量此类薄层板断裂韧性的替代方法。
An Accelerated Process Optimization Method to Minimize Deformations in Composites Using Theory-guided Probabilistic Machine Learning
Schoenholz Caleb, Zobeiry Navid
doi:10.1016/j.compositesa.2023.107842
一种基于理论指导的概率机器学习的加速复合材料变形优化方法
While aerospace manufacturing and assembly technologies have significantly evolved, challenges persist in mitigating process-induced deformations (PIDs) in composite parts. Physics-based-simulation optimization strategies have been developed to address these challenges. However, they often prove ineffective or inefficient because of the time-consuming, costly, and deterministic characterization efforts they require. This study introduces a novel characterization- and simulation-free optimization approach for predicting and minimizing PIDs in composite parts. The method uses a theory-guided machine learning (TGML) framework, consisting of limited element-level experiments and Gaussian Process Regression (GPR) with integrated closed-form domain knowledge. This paper showcases the effectiveness of the proposed TGML method for two case studies, where an optimal layup and cure cycle are found and validated after a mere six experiments and without any material characterization or simulation efforts. The method presented in this paper aims to offer a cost-efficient and generalizable process optimization procedure to potentially mitigate PIDs in composite parts.
虽然航空航天制造和装配技术有了显著的发展,但在减少复合材料零件的过程引起的变形(pid)方面仍然存在挑战。基于物理的仿真优化策略已经被开发出来以应对这些挑战。然而,由于它们所需要的耗时、昂贵和确定性的表征工作,它们常常被证明是无效的或低效的。本文介绍了一种新的无需表征和仿真的优化方法,用于预测和最小化复合材料零件的pid。该方法采用理论引导的机器学习(TGML)框架,由有限元素级实验和高斯过程回归(GPR)组成,并集成了封闭形式的领域知识。本文展示了两个案例研究中所提出的TGML方法的有效性,其中仅经过六次实验,无需任何材料表征或模拟工作,即可发现并验证最佳铺层和固化周期。本文提出的方法旨在提供一种具有成本效益和可推广的工艺优化程序,以潜在地减轻复合材料零件的pid。
Nacre-like composites with a soft thermoplastic elastomer matrix
Rajinthan Lucas, Fritz Simon, Galkov Igor, Jiang Liuyin, Fournier Sylvain, Bernard Julien, Meille Sylvain, Doitrand Aurélien, Baeza Guilhem P.
doi:10.1016/j.compscitech.2023.110302
具有柔软热塑性弹性体基体的类珍珠复合材料
We produce nacre-like composites made of a soft thermoplastic elastomer matrix reinforced by alumina platelets, as a flexible and healable alternative to stiff brick-and-mortar materials while keeping their characteristic anisotropic microstructure. Materials are manufactured using step-wise deposition and subsequent controlled evaporation of a suspension containing the polymer and the platelets. Well-aligned microstructures loaded from 15 to 65 vol.% in alumina are obtained through hot-pressing densification of the resulting composites. Remarkably, by combining calorimetry and low-field nuclear magnetic resonance techniques, we emphasize that the polymer mobility decreases significantly in spite of a lower degree of cristallinity when the platelet content is increased. This result sheds light on the origin of the limited quality of samples above 45 vol.%, opening new research directions to improve the design of organic nacre-like composites. Tensile, bending and indentation tests on samples containing up to 45 vol.% in platelets are then used to rationalize the mechanical properties variation related to the polymer state. Finally, we show that the addition of 3 vol.% of Fe nanoparticles into the composites is enough to enable their induction heating that we aim to utilize in the future as a contactless healing method.
我们生产由氧化铝片增强的柔软热塑性弹性体基体制成的类珍珠复合材料,作为刚性砂浆材料的柔性和可修复的替代品,同时保持其特征的各向异性微观结构。材料的制造采用逐步沉积和随后的控制蒸发的悬浮液含有聚合物和血小板。通过热压致密化所得到的复合材料,得到了负载从15到65体积%氧化铝的排列良好的微观结构。值得注意的是,通过结合量热法和低场核磁共振技术,我们强调了当血小板含量增加时,聚合物的迁移率显著降低,尽管结晶度降低。这一结果揭示了45 vol.%以上样品质量有限的原因,为改进有机类珍珠复合材料的设计开辟了新的研究方向。拉伸、弯曲和压痕测试的样品含有高达45体积%的血小板,然后用于合理化的机械性能变化相关的聚合物状态。最后,我们表明,在复合材料中添加3vol .%的铁纳米颗粒足以使其感应加热,我们的目标是在未来将其用作非接触式愈合方法。
Electromagnetic functionalization of mechanical lattice to metastructure with oblique incident broadband microwave absorption
Zhang Yuhui, Xu Yinfang, Yu Chen, Lei Han, Zhao Pengzhen, Huang Yixing
doi:10.1016/j.compscitech.2023.110308
斜入射宽带微波吸收下机械晶格向元结构的电磁功能化
Electromagnetic functionalization of mechanical lattice is an important method to integrate mechanical and electromagnetic properties into one structure with effective load bearing and broadband microwave absorption. Herein, the gradient lattice metastructure (GLM) is fabricated by dielectric-magnetic lossy nano composite strengthened by carbon fiber and glass fiber reinforced polymer. A large mutation genetic algorithm is developed to optimize the GLM with fine convergence property. Several large mutation modules are incorporated into the program to speed up the optimization process and improve global convergence. The measured −10 dB absorption bandwidth covers 2–5 GHz and 6.5–17.3 GHz while −9.5 dB absorption bandwidth covers 2–17.3 GHz. The oblique incident broadband absorption is achieved from normal incidence to the grazing incidence of 85° in traverse electrical (TE) and traverse magnetic (TM) polarization. Gradient lattice design is effective to overcome systemic oblique incident absorption deterioration originating from enhanced tangential electric field intensity in large incident angles. The nominal tensile strength of GLM reaches 108.4 MPa with maximum flexural load of 1.83 kN. The high electromagnetic and mechanical properties are achieved simultaneously by electromagnetic functionalization of mechanical lattice.
机械晶格的电磁功能化是将力学性能和电磁性能集成为一个结构的重要方法,具有有效的承载和宽带微波吸收能力。本文采用碳纤维和玻璃纤维增强聚合物增强的介电磁性损耗纳米复合材料制备了梯度晶格超结构(GLM)。提出了一种具有优良收敛性的大突变遗传算法。为了加快优化过程,提高全局收敛性,在程序中加入了多个大型突变模块。−10 dB的吸收带宽覆盖2-5 GHz和6.5-17.3 GHz,−9.5 dB的吸收带宽覆盖2-17.3 GHz。斜入射宽带吸收在横电极化(TE)和横磁极化(TM)中实现了从正入射到掠入射85°的斜入射宽带吸收。梯度晶格设计有效地克服了大入射角下切向电场强度增强引起的系统斜入射吸收衰减。GLM的标称抗拉强度为108.4 MPa,最大弯曲载荷为1.83 kN。通过对机械晶格进行电磁功能化,使其同时具有较高的电磁性能和力学性能。