今日更新:Composite Structures 1 篇,Composites Part A: Applied Science and Manufacturing 4 篇,Composites Part B: Engineering 1 篇,Composites Science and Technology 1 篇
Composite Structures
A kinking-based failure model for engineering simulation of compressive crushing of composite structures
Niklas Jansson, Martin Fagerström
doi:10.1016/j.compstruct.2023.117755
基于扭结的失效模型,用于复合材料结构压缩挤压的工程模拟
The use of continuum damage models is state of the art for the finite element modelling of progressive damage and failure under compressive loading in composites during e.g. crash and impact simulations. However, after failure initiation the compressive stress is quickly degraded to zero alternatively to a plateau with constant stress and at a certain point the element needs to be deleted due to the damage level or large element deformation. This effectively represent a void in the material which contrasts with reality where a fully formed kink band would be expected to have compressive properties similar to the transverse direction of the ply. To better represent this physical behaviour is here a kinking formulation developed that instead of the common constant stress plateau after initial softening features a stiffening at larger strains. This formulation has been implemented in a commercial FE-code complemented by criteria for kinking initiation and kink band broadening. The results presented show the novelty of the model in that it describes a chain of events starting with initiation of kinking, progressing to the growth of kink bands through the element and finally including an increase in stress that initiate kinking in adjacent elements.
在碰撞和冲击模拟等过程中,使用连续损伤模型对复合材料在压缩载荷作用下的渐进损伤和失效进行有限元建模是目前最先进的方法。然而,在失效开始后,压缩应力会迅速衰减为零,或者变为具有恒定应力的高原,在某一点上,由于损伤程度或较大的元素变形,需要删除元素。这实际上代表了材料中的空隙,与实际情况形成鲜明对比,完全形成的扭结带预计会具有与层板横向相似的抗压性能。为了更好地表现这种物理行为,我们在此开发了一种扭结配方,这种配方在初始软化后不再是常见的恒定应力高原,而是在较大应变时出现僵化。该公式已在商用 FE 代码中实施,并辅以扭结起始和扭结带扩展的标准。研究结果表明了该模型的新颖性,它描述了一连串的事件,从开始的扭结,到扭结带在元件中的扩展,最后包括应力的增加,从而引发相邻元件的扭结。
Composites Part A: Applied Science and Manufacturing
A strategy to fabricate hierarchical microporous architecture of polyimide nanofibrous aerogels with efficient electromagnetic wave absorption and thermal insulation
The aviation industry requires advanced aerogels that combine both electromagnetic wave (EM) attenuation and thermal insulation capabilities. This work involved the fabrication of Ti3C2Tx MXene/polyimide nanofibrous (PINF) aerogels through freeze-drying and thermal imidization. The hierarchical microporous architecture was formed by the interconnected primary pores induced by the removal of ice crystals and secondary pores from the PINF web. The unique highly porous 3D network of the nanofibrous aerogel provided well-matched impedance and enhanced multiple reflections and scattering of EM waves. The polar functional groups and defects on MXene induced dipole polarization, and the heterointerfaces between the PINFs and MXene enhanced the interfacial polarization. Consequently, the MXene/PINF aerogels exhibited efficient microwave absorption, showing a minimum reflection loss (RLmin) of -37.9 dB and an effective absorption bandwidth (EAB) of 3.3 GHz. Moreover, nanofibrous aerogels also exhibited low thermal conductivity and remarkable compression properties, making them suitable for utilization in complex environments.
Tensile and flexural mechanical attributes of hybrid carbon/basalt fiber metal laminates under various hybridization and stacking sequences
Yu Wang, Weifu Sun, Lei Cao
doi:10.1016/j.compositesa.2023.107942
不同杂化和堆叠顺序下碳/钴纤维混合金属层压板的拉伸和弯曲机械属性
In this work, experimental measurements and theoretical validation are adopted to examine the tensile and flexural behaviors of titanium-based carbon/basalt fiber metal laminates under various hybridization ratios and stacking sequences. Firstly, the mechanical response and damage patterns of fiber metal laminates (FMLs) subjected to different tensile and flexural loads have been explored. By observing the fracture surfaces of FMLs with various hybridization ratios and stacking sequences, scanning electron microscopy (SEM) has been used to identify the related microscopic damage patterns. The principal damage mechanism were attributed to fiber/matrix debonding, matrix microcrack, fiber pull-out, and delamination. Subsequently, to analyze the discreteness of experimental results and evaluate the theoretical flexural strength of FMLs under different conditions, the two-parameter Weibull statistics model for engineering application of FMLs was established. These results indicate that the tensile and flexural strength of FMLs can be improved by altering the hybridization ratios and stacking sequences. The thorough understanding of the mechanical behavior and failure mechanism of FMLs under various hybridization conditions can provide the basis for the design and utilization of FMLs structures.
Harnessing the Power of Carbon Fiber Reinforced Liquid Crystal Elastomer Composites for High-Performance Aerospace Materials: A Comprehensive Investigation on Reversible Transformation and Shape Memory Deformation
Yuliang Xia, Tong Mu, Yanju Liu, Jinsong Leng
doi:10.1016/j.compositesa.2023.107943
利用碳纤维增强液晶弹性体复合材料的力量制造高性能航空航天材料:对可逆变形和形状记忆变形的全面研究
Liquid Crystal Elastomers (LCEs) showcase transformative features making them suitable for rigorous applications, notably aerospace. However, their standalone mechanical properties often fall short. This study introduces the incorporation of carbon fiber to form a reinforced LCE composite, LCEC, aimed at enhancing mechanical performance while maintaining reversible deformation and shape memory attributes. Molecular-level analysis indicates an upsurge in overall composite performance with improved storage modulus (1.1 GPa at 25 °C), heightened reversible deformation, and better shape memory functionality. Both materials retain transformation properties under gamma-ray irradiation. This investigation into LCE and LCEC performance underscores their potential in demanding environments due to improved mechanical strength, transformability, shape memory performance, and radiation resistance. The research offers insights into micro-level alterations leading to macro-level enhancements in material properties, paving the way for future advancements in fields like robotics and aerospace.
Replacing traditional metal tanks with composite liquid oxygen (LOX) tanks would make significant contribution to the weight reduction of rockets. However, the epoxy resins (EP) matrix of composites is incompatible with LOX, which limits the application of composite LOX tanks. In this study, an aryl phosphinate diglycidyl ether (PDGEP) was synthesized using 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB) and epichlorohydrin via a single step. The structure of PDGEP was confirmed by FTIR spectra, NMR and LC-MS analysis. Meanwhile, PDGEP was introduced into biphenol A (E51) resin at different weight ratios by physical blending. When the content of PDGEP exceeded 10 phr, E51 matrix exhibited compatibility with LOX. The LOX-compatible mechanism was investigated by TGA, UL-94, TG-FTIR-MS analysis and XPS analysis. The results showed that the enhanced thermal stability under high temperatures, the quenching effects from the phosphorus-containing free radicals, the decrease of the combustible volatiles, and the shielding and protective char layer with highly carbonized aromatic networks were all responsible for the compatibility of E51 matrix with LOX. Furthermore, the flexural strength (883.31 MPa) and flexural modulus (14.83 GPa) of the carbon fiber reinforced EP10 (CF/EP10) composites at 90 K increased by 2.3% and 12.9% than those of the CF/EP0 composites. The LOX-compatible resin matrix and composites exhibit good potential for developing light-weight LOX composite cryotanks.
In order to realize high-quality and environment-friendly recycling of carbon fiber reinforced composite (CFRP) waste and high-value reuse of recycled carbon fiber (rCF), this paper proposes an additive remanufacturing process of recycled carbon fiber reinforced composite (rCFRP). The material attribute of rCF recycled by the thermally activated oxide semiconductor was analyzed and the effect of fused deposition modeling-3D (FDM-3D) printing parameters on mechanical properties of rCFRP was investigated, and FDM-3D printed rCFRP products for automotive were prepared. The results illustrate that rCF possesses the same excellent material attribute as the virgin carbon fiber, and optimizing FDM-3D printing parameters can effectively improve the mechanical properties of rCFRP. FDM-3D printed rCFRP products are of promising application in the field of automotive lightweighting due to its characteristics of personalized customization and low cost, which verifies the feasibility of the additive remanufacturing process mentioned above.
Low intrinsic thermal conductivity (TC) of polymer materials has severely limited their further applicability in electronic and electrical products. To enhance the TC, a strategy for constructing nanofiller-based thermal conductive networks by patterned self-assembly of electrospun nanofibers was first proposed in this paper. By selecting a regular metal mesh as the collector, the electrostatic field-induced directional deposition of nanofibers was achieved, thereby constructing interconnected heat transfer paths aligned in at least four directions. The in-plane TC of heat-pressed electrospun polyvinylidene fluoride (PVDF) nanofibers with 20 wt% loading of boron nitride nanosheets (BNNSs) can reach 7.27 W/(m·K). Electrical insulation of the PVDF/BNNS composites has also been confirmed, showing high volume resistivity and breakdown strength, which have increased by 460.0 % and 26.6 %, respectively, compared to pure PVDF. Finally, a double-layer composite film with waterproof and easy-cleaning characteristics was prepared for electronic device packaging. This simple and efficient preparation strategy for thermal conductive networks may bring new perspectives to thermal management applications.