There has been an urgent need to develop and analyse multi-layered composite structures with varying material properties to withstand projectile impact. The proposed study focuses on the optimization of the multi-layer composite to achieve maximum resistance/energy dissipation. This study investigates the mechanical performance of the proposed multi-layered composite configuration under high strain rate loading through a computational approach. The proposed multi-layered structure incorporates layers of reinforced concrete, boulders, an elastomer layer, an ultra-high-performance concrete panel, and a layer of steel plate. A mesoscale-based approach has been developed for the layer comprising boulders and mortar. A total of six different configurations have been considered to arrive at the most efficient one against projectile impact. Optimization of the proposed configurations has been done by utilizing the concepts of specific energy absorption and shock impedance. Additionally, the fracture and damage characteristics of each configuration are also studied. Ductile hole enlargement in the sandy soil layer, fragmentation failure in the boulders, petaling failure in the steel plate, and spalling failure in the concrete layer have been observed. Based on the specific energy absorption and shock impedance approaches, the optimum laying sequence for the ballistic impact of each material is suggested.
Carbon black (CB) is the most widely used reinforcing filler in rubber industry, but the effects of CB surface characteristics on interfacial interaction of CB-filled rubber composites are still not fully described. Combined the experimental and molecular simulation techniques, the aim of this study is to individually investigate the influence of various CB surface characteristics, such as surface area, surface crystallite size, roughness and surface energy, on CB-natural rubber (NR) interfacial interaction to obtain a deep interpretation on the properties of rubber composites. Experimental results showed that the specific surface area is the primary factor affecting overall CB-NR interaction, followed by filler network. Meanwhile, CB surface model with different roughness based on experimental parameters were constructed, and the simulation results revealed that CB-NR interfacial interaction mainly occurred at the interface 2–3 nm. The binding energy distribution on CB surface was analyzed, and rough region is weaker than crystal region and amorphous region. The strongest binding sites are located at the junction of rough region and amorphous region. The results in this study are expected to provide a theoretic guide for optimizing the CB characteristics and developing new rubber-grade CB.
Additive manufacturing and microstructure effects on thermal and mechanical properties of ply-hybrid carbon and glass fiber composites
Cristina Pascual-González, Jesús García-Moreno Caraballo, Iker Lizarralde, David Garoz Gómez, Juan P. Fernández-Blázquez
doi:10.1016/j.compositesb.2024.111446
增材制造及微观结构对复合材料热力学性能的影响
The fiber hybridization in high-strength composites is one of the most researched strategies to enhance their limited toughness. In this work, hybrid composites at laminate level by stacking together plies of carbon and glass fiber were prepared using fused filament fabrication (FFF) technique. The large void content and the poor adhesion between layers attributed to this technology are overcome by the addition of an optimized thermo-pressurized treatment. The analysis of post-processing temperature effects on the microstructural, thermal and interlaminar properties of additive manufactured hybrid composites, revealed a progressive porosity reduction preserving the dimensional accuracy. The enhancement of mechanical properties is due to different contributions that occurred during post-processing: (i) drying effect, which reduces the plasticization of the composites; (ii) improvement of interface adhesion due to the miscibility of polymers; and (iii) significant porosity reduction (below 1%). This work opens a wider space of possibilities, since FFF allows more complex designs than traditional composite manufacturing, and additionally provides an approach to promote molecular diffusion at the interface, which is the most critical region of FFF parts.
Alternative Inner Filling and Outer Surface Coating of BNNT by Tungsten(VI) Oxide for Supercapacitor Electrode
Honggu Kim, Chandan Kumar Maity, Sada Venkateswarlu, Myung Jong Kim
doi:10.1016/j.compositesb.2024.111436
超级电容器电极用氧化钨(VI)内填充和外涂BNNT的替代方法
The motivation behind this research is to address the need for advanced energy storage materials by exploring the selective filling and coating of boron nitride nanotube (BNNT) with tungsten(VI) oxide (WO3) to enhance the pseudocapacitive performance. In this study, we present a novel synthesis method that allows precise control over the extent of filling and coating, aiming to create tailored hybrid structures. Morphological and structural analysis confirm the filling and coating of BNNT by WO3. Inner filling and outer surface coating of BNNT by WO3 significantly impact on the electrochemical properties. The filling of WO3 within the BNNT can enhance the stability of the system, whereas outer surface coating of BNNT by WO3 improves the capacitive performances. The role of BNNT influences both these phenomena by acting as electrolyte transportation channel as well as stabilizing the WO3. In three electrode study, WO3 coated BNNT showed the maximum specific capacitance of 856 F/g at 1 A/g. An asymmetric supercapacitor device using WO3 coated BNNT as positive electrode revealed the maximum specific capacitance of 137 F/g at 2 A/g current density with an improved energy density of 52 W h/kg. The WO3 coated BNNT-based asymmetric supercapacitor device also showed ∼81% specific capacitance retention after the completion of 10000 GCD cycles, whereas WO3 filled BNNT-based supercapacitor device demonstrated better stability (∼94% specific capacitance retention) due to the filling and stabilization of pseudocapacitive WO3 by BNNT.
本研究的动机是通过探索氮化硼纳米管(BNNT)的选择性填充和氧化钨(WO3)涂层来提高其赝电容性能，以满足对先进储能材料的需求。在这项研究中，我们提出了一种新的合成方法，可以精确控制填充和涂层的程度，旨在创建定制的混合结构。形貌和结构分析证实了WO3对BNNT的填充和包覆。WO3内填充和外表面涂覆对BNNT的电化学性能有显著影响。在BNNT内部填充WO3可以提高体系的稳定性，而在BNNT外表面涂覆WO3则可以提高BNNT的电容性能。BNNT通过作为电解质运输通道和稳定WO3来影响这两种现象。在三电极研究中，WO3涂层的BNNT在1 A/g下的最大比电容为856 F/g。采用WO3包覆BNNT作为正极的非对称超级电容器器件在2 A/g电流密度下的最大比电容为137 F/g，能量密度提高到52 W h/kg。在完成10000次GCD循环后，WO3涂层的BNNT基非对称超级电容器器件也显示出~ 81%的比电容保留率，而WO3填充的BNNT基超级电容器器件由于BNNT填充和稳定了伪电容WO3，表现出更好的稳定性(~ 94%的比电容保留率)。
Composites Science and Technology
Constructing a special interface structure of starch/PBAT composites with a novel “many-to-many” strategy
It is a challenge to achieve a high reaction ratio of compatibilizers for improving the compatibility of the composites due to high melt viscosity and short residence time during melt processing. Inspired by the fact that xanthium seeds in nature are easy to combine with animal fur efficiently, a new "many-to-many" melting chemical reaction strategy was proposed to greatly improve the reaction ratio of compatibilizers. In this work, a polycaprolactone-based polyurethane prepolymer (PCLPU) was used to prepare compatible starch/poly(butyleneadipate-co-terephthalate) (PBAT) composites. Polyurethane nanoparticles containing a lot of -NCO groups were prepared and then reacted with tapioca starch with a lot of -OH groups in an intensive mixer to obtain starch/PBAT composite material with a special interface structure. Compared with the biocomposites without PCLPU, the PCLPU-modified biocomposites exhibited compatible morphology and excellent mechanical properties, and the reaction ratio of the PCLPU was as high as 99.2%. The special polyurethane prepolymer interface formed in the composite interacted with the hydrophilic starch granules through urethane linkages and with hydrophobic PBAT through physical PBAT-PBAT linkages. Therefore, the novel strategy used to achieve a special interface structure for improving the mechanical properties of a composite was a simple, efficient, and environmentally friendly method.
