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Sandwich structures are a class of multifunctional high-performance structural composites that have the advantages of being lightweight, of a high strength-to-weight ratio, and of high specific energy absorption capabilities. The creative design of the core along with the apposite material selection for the fabrication of the face sheet and core are the two prerequisites with encouraging areas for further expedition towards the fabrication of advanced composite sandwich structures. The current review work focused on different types of core designs, such as truss, foam, corrugated, honeycomb, derivative, hybrid, hollow, hierarchical, gradient, folded, and smart core along with different composite materials accessible for face sheet fabrication, including fiber-reinforced composite, metal matrix composite, and polymer matrix composite are considered. The joining method plays a major role for the performance evolution of sandwich structures, which were also investigated. Further discussions are aligned to address major challenges in the fabrication of sandwich structures and further enlighten the future direction of the advanced composite sandwich structure. Finally, the work is summarized with a brief conclusion. This review article provides wider guidelines for researchers in designing and manufacturing next-generation lightweight multilayer core sandwich structures.

HighlightsAligned graphene building blocks take full advantages of the outstanding properties of graphene.Comprehensive review of recent advancements in the utilization of highly aligned graphene aerogels for multifunctional applications.By systematically summarizing the controlled assembly, aligned structural attributes, quantitative characterization methods, anisotropic properties, and multifunctional applications of graphene aerogels, this review enhances understanding of the material's potential for diverse applications, offering tailored properties and novel functionalities.Stemming from the unique in-plane honeycomb lattice structure and the sp2 hybridized carbon atoms bonded by exceptionally strong carbon–carbon bonds, graphene exhibits remarkable anisotropic electrical, mechanical, and thermal properties. To maximize the utilization of graphene's in-plane properties, pre-constructed and aligned structures, such as oriented aerogels, films, and fibers, have been designed. The unique combination of aligned structure, high surface area, excellent electrical conductivity, mechanical stability, thermal conductivity, and porous nature of highly aligned graphene aerogels allows for tailored and enhanced performance in specific directions, enabling advancements in diverse fields. This review provides a comprehensive overview of recent advances in highly aligned graphene aerogels and their composites. It highlights the fabrication methods of aligned graphene aerogels and the optimization of alignment which can be estimated both qualitatively and quantitatively. The oriented scaffolds endow graphene aerogels and their composites with anisotropic properties, showing enhanced electrical, mechanical, and thermal properties along the alignment at the sacrifice of the perpendicular direction. This review showcases remarkable properties and applications of aligned graphene aerogels and their composites, such as their suitability for electronics, environmental applications, thermal management, and energy storage. Challenges and potential opportunities are proposed to offer new insights into prospects of this material.

The demand for lightweight, high-performance materials with electromagnetic shielding capability is increasing, particularly in aerospace, defense, and infrastructure applications. This study introduces a novel gypsum-based composite system enhanced with carbon black (CB), magnetite (Fe3O4), boron nitride (BN), and hybrid glass-basalt fibers to simultaneously improve mechanical strength and electromagnetic wave absorption. A limited experimental dataset of 13 formulations was extended to 260 using physics-consistent data augmentation. Multi-objective optimization was then performed using the Artificial Bee Colony (ABC) algorithm to maximize compressive, flexural, and splitting tensile strengths while minimizing return loss in the 8–12 GHz (X-band) range. The optimized formulation (85% gypsum, 15% resin, 6.8% CB, 18.5% Fe3O4, 2% BN, 1% glass fiber, 0.5% basalt fiber) achieved 34.41 MPa compressive strength (+6.1%), 7.71 MPa flexural strength (+5.3%), and 4.45 MPa splitting tensile strength (+5.7%). Simultaneously, the minimum return loss improved from −22.5 to −24.8 dB, resulting in an enhancement of electromagnetic absorption by 10.2% at 9.72 GHz. Validation tests confirmed the model's accuracy within a 1.35% margin of error. This hybrid methodology, which combines experimental science, AI-driven data expansion, and bio-inspired optimization, offers a scalable and cost-effective route to multifunctional composite design. The findings are directly relevant for radar-absorbing structures, EMI shielding in electronics, and smart civil infrastructure. •Radar absorption was increased by 10.22 %, while compressive strength was increased by 6.05 % simultaneously.•The best mix achieved a return loss of −24.8 dB and a compressive strength of 34.4 MPa.•Experimental validation confirmed predictions with 1.35 % accuracy.

The need to recycle carbon-fibre-reinforced composite polymers (CFRP) has grown significantly to reduce the environmental impact generated by their production. To meet this need, thermoreversible epoxy matrices have been developed in recent years. This study investigates the performance of an epoxy vitrimer made by introducing a metal catalyst (Zn[sup.2+]) and its carbon fibre composites, focusing on the healing capability of the system. The dynamic crosslinking networks endow vitrimers with interesting rheological behaviour; the capability of the formulated resin (AV-5) has been assessed by creep tests. The analysis showed increased molecular mobility above a topology freezing temperature (T[sub.v]). However, the reinforcement phase inhibits the flow capability, reducing the flow. The fracture behaviour of CFRP made with the vitrimeric resin has been investigated by Mode I and Mode II tests and compared with the conventional system. The repairability of the vitrimeric CFRP has been investigated by attempting to recover the delaminated samples, which yielded unsatisfactory results. Moreover, the healing efficiency of the modified epoxy composites has been assessed using the vitrimer as an adhesive layer. The joints were able to recover about 84% of the lap shear strength of the pristine system.

Shape memory polymer (SMP) is a kind of material that can sense and respond to the changes of the external environment, and its behavior is similar to the intelligent reflection of life. Electrospinning, as a versatile and feasible technique, has been used to prepare shape memory polymer fibers (SMPFs) and expand their structures. SMPFs show some advanced features and functions in many fields. In this review, we give a comprehensive overview of SMPFs, including materials, fabrication methods, structures, multifunction, and applications. Firstly, the mechanism and characteristics of SMP are introduced. We then discuss the electrospinning method to form various microstructures, like non-woven fibers, core/shell fibers, hollow fibers and oriented fibers. Afterward, the multiple functions of SMPFs are discussed, such as multi-shape memory effect, reversible shape memory effect and remote actuation of composites. We also focus on some typical applications of SMPFs, including biomedical scaffolds, drug carriers, self-healing, smart textiles and sensors, as well as energy harvesting devices. At the end, the challenges and future development directions of SMPFs are proposed.

Multifunctional composites can be achieved by adding two different fillers with complementary properties to a polymer matrix. In this work, novel tri-composite multifunctional materials based on the incorporation of dielectric BaTiO3 (BT) and magnetic CoFe2O4 (CFO) nanoparticles into poly(vinylidene fluoride) (PVDF) have been developed with enhanced dielectric and magnetic responses for applications in areas such as energy harvesting, sensors and actuators. The microstructure, polymer phases as well as the thermal stability of the samples were investigated, showing the independence of the polymer crystallization phases, degree of crystallinity and melting temperature on filler type and contents. Further, independent of the type of the filler, its content improves the degradation temperature of the tri-composites. The magnetic properties and electrical conductivity of the tri-composites are correlated with the increase in the content of the CFO filler, while the dielectric response is mainly determined by the interfacial polarization. A high dielectric constant of 26 at 1 kHz and a magnetization of 5.7 emu * g−1 are obtained for a sample of 10 wt% CFO–10 wt% BT/PVDF, which was used for the demonstration of the suitability of the materials for magnetic deformation sensing. This work provides pathways for the development of tri-composites based on PVDF with high dielectric constant and magnetic properties for application in areas such as sensors and actuators.Graphic abstract

The demand for additively manufactured polymer composites with increased specific properties and functional microstructure has drastically increased over the past decade. The ability to manufacture complex designs that can maximize strength while reducing weight in an automated fashion has made 3D-printed composites a popular research target in the field of engineering. However, a significant amount of understanding and basic research is still necessary to decode the fundamental process mechanisms of combining enhanced functionality and additively manufactured composites. In this review, external field-assisted additive manufacturing techniques for polymer composites are discussed with respect to (1) self-assembly into complex microstructures, (2) control of fiber orientation for improved interlayer mechanical properties, and (3) incorporation of multi-functionalities such as electrical conductivity, self-healing, sensing, and other functional capabilities. A comparison between reinforcement shapes and the type of external field used to achieve mechanical property improvements in printed composites is addressed. Research has shown the use of such materials in the production of parts exhibiting high strength-to-weight ratio for use in aerospace and automotive fields, sensors for monitoring stress and conducting electricity, and the production of flexible batteries.

Additive manufacturing, with its wide range of printable materials, and ability to minimize material usage, reduce labor costs, and minimize waste, has sparked a growing enthusiasm among researchers for the production of advanced multifunctional composites. This review evaluates recent reports on polymer composites used in 3D printing, and their printing techniques, with special emphasis on composites containing different types of additives (inorganic and biomass-derived) that support the structure of the prints. Possible applications for additive 3D printing have also been identified. The biodegradation potential of polymeric biocomposites was analyzed and possible pathways for testing in different environments (aqueous, soil, and compost) were identified, including different methods for evaluating the degree of degradation of samples. Guidelines for future research to ensure environmental safety were also identified.

The significant contribution of super lubrication is to achieve ultra‐low friction in the friction pair, improving the wear resistance of the contact surface and thus achieving energy savings and environmental protection. Despite numerous experimental studies exploring the mechanism contributing to superlubrication, there is a relative scarcity of overall generalizations regarding the recent development of 0D–3D nanomaterials in superlubrication. Therefore, this paper systematically reviews the latest research progress on nanomaterials for achieving ultra‐low friction and wear in solid/liquid lubrication systems focusing on the structural characteristics of 0D‐3D nanomaterials. The important role of nanomaterial dispersion in the superlubrication steady state is discussed in detail, and recommendations are made for the key challenges of future engineering‐scale macroscopic superlubrication applications. This paper systematically introduces the characteristics and functions of 0D‐3D nanomaterials in super‐lubrication, analyzes the lubrication mechanism of these nanomaterials, and prospects the energy‐saving and environmental benefits brought by their progress in this field. Furthermore, it explores the main challenges facing this field and provides recommendations for future applications.