今日更新:Composites Part A: Applied Science and Manufacturing 1 篇,Composites Part B: Engineering 2 篇
Promoting bridging in adhesively bonded composites with polymer inserts: A computational perspective
Ditho Pulungan, Sofyan Andika, Tatacipta Dirgantara, Riza Wirawan, Hermawan Judawisastra, Satrio Wicaksono
doi:10.1016/j.compositesa.2024.108107
用聚合物插入物促进粘合复合材料中的桥接:计算视角
Preventing catastrophic failure due to delamination in adhesively bonded carbon fiber reinforced polymer (CFRP) is crucial to enhancing the reliability of structures. Experimental evidence from another study demonstrated that introducing inserts into the adhesive bond line creates bridging, effectively arresting the delamination process. In this paper, a numerical model was proposed to mimic the experiment and then utilized for conducting parametric studies. An embedded cell approach was adopted, representing a double cantilever beam (DCB) with linear-elastic continuum shell elements, beam elements for the bridging bundles, and connector elements for the adhesive. The crack propagation was initiated with adhesive failure and subsequently followed by bridging bundle failure. The numerical simulation results closely replicated the experiment’s global response in the force–displacement curve, thereby effectively validating the existence of the bridging effect. Furthermore, our study revealed that enhancing the adhesive strength and insert ductility can further improve crack resistance.
防止因粘合碳纤维增强聚合物(CFRP)分层而导致的灾难性失效对于提高结构的可靠性至关重要。另一项研究的实验证据表明,在粘合剂粘合线中引入插入物可产生桥接,有效阻止分层过程。本文提出了一个数值模型来模拟实验,然后利用该模型进行参数研究。该模型采用嵌入式单元方法,用线性弹性连续壳元素表示双悬臂梁 (DCB),用梁元素表示桥接束,用连接器元素表示粘合剂。裂纹扩展始于粘合剂失效,随后桥接束失效。数值模拟结果与实验中力-位移曲线的全局响应密切相关,从而有效验证了桥接效应的存在。此外,我们的研究还发现,提高粘合强度和插入延展性可进一步改善抗裂性。
4D printed multifunctional wearable strain sensors with programmable sensing characteristics
Jifeng Zhang, Xue Yang, Wangxuan Li, Hongpei Liu, Zhifu Yin, Yangbo Chen, Xueli Zhou
doi:10.1016/j.compositesb.2024.111346
具有可编程传感特性的 4D 印刷多功能可穿戴应变传感器
Combining 4D-printed bilayer actuators with the slit structure and sensing capabilities unique to the process further promotes the use of 4D printing in biomedical devices, human-computer interaction, intelligent self-protection devices, and humanoid robots. In this study, we propose an adaptive multifunctional strain sensor (AMSS) 4D printing strategy based on the shape memory properties of polylactic acid (PLA), a bioslit structural sensing unit, and a bi-directional deformation design of a bilayer structure. The obtained AMSS was shown to have excellence sensitivity to strain, mechanical, and temperature stimuli. In particular, thanks to the 3D printed slit structure and phase transition properties of the PLA printing layer, the AMSS macro-microstructure can be precisely tuned, and its sensing performance is shown to be intelligently programmable. The built-in structural design-induced macro-deformation enables AMSS to adaptively fit human joint surfaces for full-range human motion recognition. In addition, the close correlation of strain-sensing during AMSS shape transformation enables position self-sensing and strain self-sensing of AMSS. Further, through the integration and separation of resistive signals, we are able to recognize temperature and mechanical stimuli. Finally, we integrate the wireless sensing module into the AMSS to improve the portability and wearability of the sensor.
将 4D 印刷双层致动器与该工艺特有的缝隙结构和传感功能相结合,可进一步促进 4D 印刷在生物医学设备、人机交互、智能自我保护设备和仿人机器人中的应用。在这项研究中,我们基于聚乳酸(PLA)的形状记忆特性、生物光结构传感单元和双层结构的双向变形设计,提出了一种自适应多功能应变传感器(AMSS)4D 打印策略。结果表明,获得的 AMSS 对应变、机械和温度刺 激具有卓越的灵敏度。特别是,得益于三维打印狭缝结构和聚乳酸打印层的相变特性,AMSS 的宏观微观结构可以被精确调整,其传感性能被证明是智能可编程的。内置结构设计引起的宏观变形使 AMSS 能够自适应地贴合人体关节表面,从而实现全方位的人体运动识别。此外,AMSS 形状变换过程中的应变感应密切相关,实现了 AMSS 的位置自感应和应变自感应。此外,通过整合和分离电阻信号,我们还能识别温度和机械刺 激。最后,我们将无线传感模块集成到 AMSS 中,以提高传感器的便携性和可穿戴性。
A continuum damage model for Mg/Al composite sheets rolling: Theoretical development and application
Tao Wang, Chenchen Zhao, Gang Zhang, Wenqiang Zhao, Qingxue Huang
doi:10.1016/j.compositesb.2024.111347
镁铝复合材料板材轧制连续损伤模型:理论发展与应用
Edge cracks, which are typical formability defects, severely limit the widespread application of Mg/Al composite sheets. Accurate prediction of damage is crucial for understanding the underlying mechanisms behind crack formation. In this study, a continuum damage model that incorporates the stress-state function and effective equivalent plastic strain into the standard Lemaitre model is proposed. This enhanced model effectively addresses the issues of damage-evolution linearization and tension–compression asymmetry in the standard Lemaitre model. Thus, it can be successfully applied to predict the fracture response of ductile composite materials under pressure-forming conditions. Considering AZ31B Mg alloy and 5052 Al alloy as experimental materials, physical experiments and numerical validation are performed under a 50% reduction and 350 °C. The findings show that the proposed model effectively captures crack initiation and propagation during the rolling process, with errors of only 23.1% and 19.9% for average crack quantity and length, respectively. Results of numerical analysis reveals that the high-stress triaxiality at the edge of the sheet contributes significantly to crack formation. Additionally, the strain along the normal direction in the Al alloy significantly affects crack propagation and the formation of serrated cracks on the side of Mg alloy. This study provides important theoretical foundations for the development of Mg-based composite sheets.
边缘裂纹是典型的成型缺陷,严重限制了镁/铝复合材料板材的广泛应用。准确预测损伤对于理解裂纹形成背后的基本机制至关重要。本研究提出了一种将应力状态函数和有效等效塑性应变纳入标准勒梅特模型的连续损伤模型。这种增强型模型有效地解决了标准 Lemaitre 模型中损伤演变线性化和拉伸-压缩不对称的问题。因此,该模型可成功用于预测压力成型条件下韧性复合材料的断裂响应。以 AZ31B Mg 合金和 5052 Al 合金为实验材料,在减薄 50%、温度为 350 ℃ 的条件下进行了物理实验和数值验证。结果表明,所提出的模型能有效捕捉轧制过程中裂纹的产生和扩展,平均裂纹数量和长度的误差分别仅为 23.1% 和 19.9%。数值分析结果表明,板材边缘的高应力三轴性在很大程度上导致了裂纹的形成。此外,铝合金沿法线方向的应变也对裂纹扩展和镁合金侧面锯齿状裂纹的形成产生了重要影响。这项研究为镁基复合材料板材的开发提供了重要的理论基础。