Lightweight Structural Materials Research Articles

Deployment analysis of composite thin-walled lenticular tubes with effect of storage time and temperature

Composite Thin-walled Lenticular Tube (CTLT) is increasingly utilized in small satellites missions as a lightweight, foldable, and rollable structural material that facilitates the construction of large deployable systems. The CTLT is initially flattened and coiled around a central hub for storage before launch, during which elastic energy is stored as deformation energy, allowing it to be self-deployed on demand for use in orbit. This work presents a comprehensive investigation into the coiling, storage and deployment behaviors of CTLT that wraps around a central hub. A nonlinear explicit dynamic finite element model was developed with both deformable CTLT and rigid-bodies mechanisms including the central hub and guide rollers, as well as the complex interactions among them. The coiling mechanics characteristics such as stored strain energy and rotational moment were presented and validated against experimental data in the literature. Then, the dynamic deployment behaviors were analyzed in terms of two different deployment methods, namely, controlled deployment and free deployment. The effect of material property change during storage was also discussed through numerical experiments.

Evaluation of mechanical and corrosion properties of AZ91-GNP nanocomposites fabricated using the SMART/MA process

Mg and its alloys are lightweight metallic materials with a low density and high specific strength. The Mg alloy AZ91 is used as a lightweight structural material in automobiles because of its high mechanical strength and corrosion resistance. In Mg-based nanocomposites, wherein graphene nanoplatelets (GNPs) are added as reinforcement materials to the AZ91 matrix, severe agglomeration occurs in the process of mixing the GNPs and Mg alloy powders owing to extensive van der Waals bonds between the GNP layers. This agglomeration of GNPs in the Mg alloy acts as a crack initiation site and lowers the mechanical properties and corrosion resistance of the alloy. In this study, a double-powder mixing process called SMART/MA is developed to inhibit GNP agglomeration. This process produces an AZ91-based composite with a few layers of GNP evenly dispersed throughout the matrix, which improves its mechanical properties and corrosion resistance.

Lightweight and high hardness (AlNbTiVCr)100-xNix high entropy alloys reinforced by Laves phase

Tailoring the phase constituents by alloying is an available exploration route to improve the integrated mechanical properties. (AlNbTiVCr)100-xNix (x = 0, 0.5, 1, 1.5, and 2, at.%, simplify as Ni0, Ni0.5, Ni1, Ni1.5, and Ni2 alloy, respectively) high entropy alloys were designed and prepared. The effect of Ni on phase formation, microstructure and mechanical properties is evaluated. The addition of Ni transforms the alloys microstructure from a single BCC phase to a mixture of BCC phase, C14 Laves phase and C15 Laves phase. The doping of Ni promotes precipitation of Nb and Cr, resulting in atomic size mismatch and shear modulus mismatch caused by Nb and Cr, respectively. The volume fraction of the Laves phase gradually increases. In room temperature compression test, Ni1.5 alloy exhibits a better combination of compressive strength of 1906.2 MPa, fracture strain of 15.2%, and high specific strength of 330.9 MPa/g × cm−3. When Ni content is 2 at. %, Vickers hardness reaches the maximum value of 740.8 HV. An improvement in compressive strength and Vickers hardness is due to solid solution strengthening and precipitated phase strengthening. This study provides important experience for the design and preparation of lightweight structural materials for practical applications.

An all-natural fire-resistant bioinspired cellulose-based structural material by external force-induced assembly

Natural wood is a widely used structural building material because of its light weight and high strength, yet it is limited by the ignitability. Traditional top-down strategies can delay the burning time of wood-derived materials but hardly reach incombustible performance. Here, we develop a bottom-up external force-induced assembly strategy to fabricate nonburning nacre-mimetic structural materials based on the shear-thinning behavior of cellulose nanofibers, the main component of wood. The highly ordered brick-and-mortar structure endows the structural material with excellent comprehensive mechanical properties and oxygen insulation, giving it better specific flexural strength [143 MPa/(Mg m−3)] and limit oxygen index (100%) than various natural woods. Furthermore, the house model, made of bioinspired structural materials, does not burn or collapse even in a butane blowtorch flame (more than 1100 °C), demonstrating its great potential as a sustainable, lightweight, strong, and safe structural building material.

True self-reinforced composites enabled by tuning of molecular structure for lightweight structural materials in future mobility

The development of vehicle bodies based on lightweight structural composites is urgently required to upgrade electric cars and to commercialize urban air mobility. Self-reinforced composites (SRCs) are attracting attention due to their advantages in terms of price, lightness, disposal and recycling compared to carbon fiber-reinforced polymers (CFRPs). In this study, a new concept for 100% polypropylene (PP) SRC was proposed to simultaneously improve the adhesive, tensile and impact properties of SRCs without undermining the advantages of SRCs. For this implementation, a facile engineering strategy using quad screw extrusion (QSE) capable of generating high shear stress was employed to modify the melting temperature and impregnation properties of the PP matrix via controlling polymer chain structure. As the screw rotation speed of QSE increased, low molecular weight polymer chains with uniform chain lengths were prepared, which led to a decrease in the melting temperature of the PP matrix and an increase in the flowability and impregnation property of the matrix. Using this strategy, the adhesive strength, tensile strength and impact resistance of the optimized SRC improved by 333%, 228%, and 2700%, respectively. Racing drone flight experiments with the SRC and CFRP frames illustrated the advantages of the SRC frame such as the increase of the flight time due to low density of the SRC, the excellent impact resistant characteristics (which improves user safety), and the superior electrical insulation properties suitable for frequency transmission and reception. Therefore, the proposed SRC can be an ideal choice as a lightweight structural material for future mobility.

Lightweight Structural Biomaterials with Excellent Mechanical Performance: A Review

The rational design of desirable lightweight structural materials usually needs to meet the strict requirements of mechanical properties. Seeking optimal integration strategies for lightweight structures and high mechanical performance is always of great research significance in the rapidly developing composites field, which also draws significant attention from materials scientists and engineers. However, the intrinsic incompatibility of low mass and high strength is still an open challenge for achieving satisfied engineering composites. Fortunately, creatures in nature tend to possess excellent lightweight properties and mechanical performance to improve their survival ability. Thus, by ingenious structure configuration, lightweight structural biomaterials with simple components can achieve high mechanical performance. This review comprehensively summarizes recent advances in three typical structures in natural biomaterials: cellular structures, fibrous structures, and sandwich structures. For each structure, typical organisms are selected for comparison, and their compositions, structures, and properties are discussed in detail, respectively. In addition, bioinspired design approaches of each structure are briefly introduced. At last, the outlook on the design and fabrication of bioinspired composites is also presented to guide the development of advanced composites in future practical engineering applications.

Comparative study on the microgalvanic corrosion phenomena of WE43 alloy in Cl- / HCO3- / CO32- environments

With rare-earth elements gradually coming into view, Mg-rare earth alloys like WE43, which inherit the properties of Mg alloys as lightweight structural materials, are gradually being explored. Anomalous preferential dissolution of the second phase of Mg-rare earth alloy (WE43) in the CO32- environment was identified. Further research revealed that this anomaly was due to the anodic role of the second phase in the microgalvanic corrosion with Mg-matrix protection. The interesting thing is that the second phase as cathode role was found in the HCO3- environment, like the phenomenon in Cl- environment, and the value of pH was not the decisive fact. The different microgalvanic corrosion behavior could be attributed to the reaction between metal atoms and ions in solution. In addition, the surface film of WE43 was systematically studied in three environments and specific corrosion models were developed for each environment.

Biomimetic Gradient Bouligand Structure Enhances Impact Resistance of Ceramic-Polymer Composites.

Biological materials relied on multiple synergistic structural design elements typically exhibit excellent comprehensive mechanical properties. Hierarchical incorporation of different biostructural elements into a single artificial material is a promising approach to enhance mechanical properties, but remains challenging. Herein, a biomimetic structural design strategy is proposed by coupling gradient structure with twisted plywood Bouligand structure, attempting to improve the impact resistance of ceramic-polymer composites. Via robocasting and sintering, kaolin ceramic filaments reinforced by coaxially aligned alumina nanoplatelets are arranged into Bouligand structure with a gradual transition in filament spacing along the thickness direction. After the following polymer infiltration, biomimetic ceramic-polymer composites with a gradient Bouligand (GB) structure are eventually fabricated. Experimental investigations reveal that the incorporation of gradient structure into Bouligand structure improves both the peak force and total energy absorption of the obtained ceramic-polymer composites. Computational modeling further suggests the substantial improvement in impact resistance by adopting GB structure, and clarifies the underlying deformation behavior of the biomimetic GB structured composites under impact. This biomimetic design strategy may provide valuable insights for developing lightweight and impact-resistant structural materials in the future.

Microstructure and properties characterization of laser-cladded Cu[sbnd]Al alloy coatings on Mg[sbnd]Li alloy

MgLi alloys have a wide application in the lightweight structure materials on account of their ultra-light-weight, good machinability and high specific strength. However, the low strength, insufficient wear and corrosion resistances of MgLi alloys have become a critical problem that hinders their applications. In order to achieve excellent wear and corrosion properties, LC-Cu3Al, LC-Cu6Al and LC-Cu9Al coatings are designed and prepared on MgLi alloy substrates in this study. The phase structure, microstructure, hardness, wear and corrosion properties of CuAl alloy coatings are investigated in detail. The results show that a good metallurgical bond is achieved between the CuAl alloy coatings and the substrates. LC-Cu6Al coating's hardness, wear and corrosion properties are the best. Compared with the MgLi alloy substrate, the average hardness of LC-Cu6Al coating increases by 6.75 times, while the wear volume decreases by 88.32 % and the corrosion current density decreases by two orders of magnitude. The results suggest that using laser cladding CuAl alloy coatings is an excellent strategy to enhance the surface properties of MgLi alloy.

Wood biomimetics: Capturing and simulating the mesoscale complexity of willow using cross-correlation reconstruction algorithm and 3D printing

Biomimetics -using nature to inspire innovation- has resulted in the development of many novel materials. Wood, nature’s light-weight structural material, defies mimicry at multiple scales, but its design features have been abstracted and used to develop honeycomb composites of limited geometric complexity. In this paper we demonstrate how it is possible to more completely biomimic wood, capture its exquisite mesoscale features and reproduce its mechanical properties. We utilised micro computed tomography (XCT) to image willow wood and used a novel cross-correlation reconstruction algorithm to mimic its 3D microstructure using minimal information. The mechanical properties of the simulated wood were compared with those derived from parent XCT data using finite-element simulations and testing of 3D printed samples of both wood types. The porosity and connectivity of both sample types was also compared. Our reconstruction algorithm was able to capture critical structural elements of willow wood with a high degree of fidelity, while mechanical properties of both wood types were closely matched. We conclude that our image-based stochastic modelling biomimetics offers a unique approach to capturing the mesoscale complexity of wood and will lead to new opportunities for designing novel materials inspired by xylotomy and powered by fast and high-performance computation.

B4C–(Ti0.9Cr0.1)B2 composites with excellent specific hardness and enhanced toughness

AbstractDense and light B4C–(Ti0.9Cr0.1)B2 composites with excellent mechanical properties were designed and reactively densified from boron, TiC, and Cr3C2 powder mixtures by spark plasma sintering in this work. Due to solid solution effects, the as‐obtained B4C–(Ti0.9Cr0.1)B2 composite exhibited obviously enhanced hardness (43.2 ± 3.0 GPa at 9.8 N) and higher specific hardness (12.82 GPa cm3 g−1) together with improved flexural strength (663 ± 39 MPa) and fracture toughness (KIC, 5.40 ± 0.25 MPa m1/2), compared to the counterparts such as B4C–TiB2 composite and B4C. Toughening contributions in the as‐sintered ceramics were quantitatively analyzed, and higher KIC in B4C–(Ti0.9Cr0.1)B2 was mainly due to their larger initial fracture toughness and compressive stress toughening. The combination of these properties makes B4C–(Ti0.9Cr0.1)B2 composites exhibit great potentials in the application as lightweight structural materials. This work provided an inspiration to achieve lightweight materials with high performance through doping minor‐amount atoms into the matrix.

Scalable Manufacturing of Mechanical Robust Bioinspired Ceramic-Resin Composites with Locally Tunable Heterogeneous Structures.

Lightweight structural materials with a unique combination of high stiffness, strength, toughness, and hardness, are highlydesired yet challenging to be artificially fabricated. Biological structural materials, on the other hand, ingeniously integrate multiple mutually exclusive mechanical properties together relying on their hierarchically heterogeneous structures bonded with gradient interfaces. Here, a scalable bottom-up approach combining continuous nanofiber-assisted evaporation-induced self-assembly with laminating, pressure-less sintering and resin infiltration is reported to fabricate bioinspired heterogeneous ceramic-resin composites with locallytunable microstructure to fulfill specific properties. A gradient interlayer isintroduced to provide a gradual transition between adjacent heterogeneous layers, effectively alleviating their property mismatch. The optimized heterogeneous nacre-like composite, as a demonstration, exhibits an attractive combination of low density (≈2.8gcm-3 ), high strength (≈292MPa), toughness (≈6.4MPam1/2 ), surface hardness (≈1144 kgfmm-2 ) and impact-resistance, surpassing the overall performance of engineering alumina. This material-independent approach paves the way for designing advanced bioinspired heterogeneous materials for diverse structural and functional applications.

Microstructure and mechanical properties of carbon nano-onions reinforced Mg-based metal matrix composite prepared by friction-stir processing

In consideration of the increasing demand for lightweight structural metal materials, it is essential to develop Mg-based metal matrix composite (MMC) with well-matched strength and ductility. In this study, carbon nano-onion (CNO) reinforced AZ31B Mg alloy MMC was successfully fabricated via friction stir processing (FSP). The microstructure and mechanical properties of the FSP CNO/AZ31B MMC were investigated. The obtained results showed that a homogeneous fine grain structure was achieved in the stir zone without gaps and microcracks. The grain refinement mechanisms were attributed to continuous and discontinuous dynamic recrystallization. The CNOs also played a critical role in the activation of {10−12} twinning behaviour. {10−12} twins can not only further refine the recrystallized grains but also reduce the basal texture intensity. The FSP CNO/AZ31B MMC exhibited enhanced yield strength due to the combined effects of grain boundary strengthening, dislocation strengthening, Orowan strengthening, and load bearing mechanism of reinforcements. Owing to the {10−12} twins and CNO induced back-stress strengthening, the FSP CNO/AZ31B MMC preformed improved strain hardening capacity. The yield strength and fracture elongation were enhanced by 14 % and 11.8 % compared with those of the matrix material, respectively, indicating that the strength and ductility were simultaneously improved due to the addition of CNO reinforcement.

Ultra-lightweight living structural material for enhanced stiffness and environmental sensing.

Natural materials such as bone, wood, and bamboo can inspire the fabrication of stiff, lightweight structural materials. Biofilms are one of the most dominant forms of life in nature. However, little is known about their physical properties as a structural material. Here we report an Escherichia coli biofilm having a Young's modulus close to 10​GPa with ultra-low density, indicating a high-performance structural material. The mechanical and structural characterization of the biofilm and its components illuminates its adaptable bottom-up design, consisting of lightweight microscale cells covered by a dense network of amyloid nanofibrils on the surface. We engineered E.coli such that 1) carbon nanotubes assembled on the biofilm, enhancing its stiffness to over 30​GPa, or that 2) the biofilm sensitively detected heavy metal as an example of an environmental toxin. These demonstrations offer new opportunities for developing responsive living structural materials to serve many real-world applications.

Fully Wood-Based Transparent Plates with High Strength, Flame Self-Extinction, and Anisotropic Thermal Conduction

Glasses and transparent plastics are used as daylighting face materials in buildings and vehicles. However, these transparent materials are mechanically inferior to other structural members such as metals, concretes, and fiber-reinforced plastics and have no contribution to the load-bearing capacities of whole structures incorporating them. Herein, we report clearly transparent and mechanically strong plate materials (haze 8%, strength 256 MPa) comprising solely wood-derived cellulose nanofibers (CNFs) with carboxy functionality. These plates have a millimeter thick laminated structure and are united by self-adhesive forces of the CNFs. Their strength is comparable to those of light-weight structural materials, such as aluminum alloys and glass fiber-reinforced plastics, while the CNF plates are even lighter. The plates feature excellent flame self-extinguishing properties due to the carboxylate structure of CNFs and further show anisotropic thermal conduction between the in-plane and out-of-plane directions. A strategy for overcoming the high water absorption, a major issue of CNF materials, through the counterion design of carboxy groups is also demonstrated.

Eutectic high entropy alloy syntactic foam

High-strength metallic foams have a wide range of applications in engineering as lightweight structural and energy-absorbing materials. However, it is challenging to obtain metallic foam with both good energy absorption performance and high strength. Here, we developed a novel metal matrix syntactic foam fabricated with AlCoCrFeNi2.1 eutectic high entropy alloy and alumina cenospheres that exhibits a remarkable combination of high strength and energy absorption performance under both quasi-static and dynamic compression. The porous structure of syntactic foam fully exploits the properties of the AlCoCrFeNi2.1 alloy matrix with a unique FCC/B2 dual-phase eutectic microstructure and thus yields exceptional performance. We discovered that this dual-phase microstructure not only provides high strength but also allows the pores to collapse in a progressive and diffusive way, which enables the formation of a high and smooth energy absorption platform. It is found that the heterogeneity between the two phases in the matrix can provide back stress strengthening, and it also induces multiple micro shear bands and microcracks as additional energy dissipation modes as the deformation proceeds. This unique mechanism ensures the strength of microstructures and makes them fracture promptly, which causes the balance of strengthening and softening on the macro scale. This work opens the avenue for developing advanced high-strength lightweight structural and energy-absorbing materials.

Exploring the Effect of Different Waste Fillers in Manufactured Sustainable Plastic Aggregates Matrix on the Structural Lightweight Green Concrete

The infrastructure demands for mega cities, urbanization and environmental concerns are pushing for smart and sustainable solutions. Structural lightweight concrete is gaining popularity in the concrete industry because of its intrinsic properties of resisting the load and being lighter in weight. Therefore, in this study, a green structural lightweight concrete was targeted by fabricating a plastic-based aggregate incorporating different industrial by-products to reduce the carbon tracks along with an alternate lightweight structural material. Thus, the compatibility of the different industrially by-products (dune dust, fly ash, and quarry dust) with plastic to produce a sustainable structural lightweight aggregate was evaluated in this study. The major physical characteristics of manufactured aggregates along with fresh, hardened, and durability properties of concretes were studied. Results revealed that altering the filler type had altered the texture and size of the developed aggregate. The aggregates developed with dune dust showed the largest particle size, bulk specific gravity, and strength while the ones with fly ash had the smallest size and water absorption. The decrease in the strength was found to be 24.7, 43.6, and 29% for dune dust, fly ash, and quarry dust respectively, once the filler percentage was increased from 50 to 70%. Additionally, all the concretes incorporating developed aggregates have evidently demonstrated their likely usage in structural lightweight applications by complying with ASTM C330/C330M-14 for compressive, flexural, and splitting tensile strength values, in addition to the improved durability behavior.

Achieving exceptional high-temperature resistant Al matrix composites via two-dimensional BN pinning grain rotation

Aiming to develop a new generation of lightweight, high-strength, and heat-resistant structural materials, BNNSs/Al composites were fabricated based on powder metallurgy process. TEM results demonstrated that BNNSs were mainly distributed at grain boundaries, forming BNNSs-AlN-Al transition interface during the sintering process. The Al grains of BNNSs/Al composites maintained stable at temperatures up to 573 K and achieved unprecedented high-temperature tensile strength of about 329 ± 6 MPa. The experimental and simulation results revealed that the reduction of tensile strength of Al matrix at high temperature was due to the decrease of grain boundary stability, which led to grain rotation and stress concentration near grain boundary. However, BNNSs with unique two-dimensional morphology can effectively suppress grain boundary diffusion and grain boundary motion, which retarded the softening of Al grains. More importantly, the strongly bonded BNNSs-AlN-Al transition interface can enhance drag effect of BNNSs, which effectively limits the grain rotation during the high-temperature deformation and stimulates the coordinated intragranular plastic deformation of Al grains. Thus, the BNNSs/Al composite maintained a high level of deformability and efficient load transfer even at 573 K. Our findings provide a promising route to extending the application of Al matrix composites in the field of high-temperature structures.

Probing the Influence of Surface Chemical Functionalization on Graphene Nanoplatelets-Epoxy Interfacial Shear Strength Using Molecular Dynamics

In this work, a characterization study of the interfacial interaction between different types of graphene nanoplatelets and an epoxy matrix is computationally performed. To quantify the discrete mutual graphene-epoxy "interfacial interaction energy" (IIE) within the nanocomposite, molecular dynamics simulations with a reactive force field are performed on a localized model of the suggested nanocomposite. Pull-out molecular dynamics simulations are also performed to predict the interfacial shear strength between the two constituents. The results indicate a significant increase in interfacial adhesion of functionalized nanoplatelets with the hosting epoxy matrix relative to virgin graphene nanoplatelets. The obtained results also demonstrate a dramatic increase in the interfacial interaction energy (IIE) (up to 570.0%) of the functionalized graphene/epoxy nanocomposites relative to the unmodified graphene/epoxy nanocomposites. In the same context, the surface functionalization of graphene nanoplatelets with the polymer matrix leads to a significant increase in the interfacial shear strength (ISS) (up to 750 times). The reported findings in this paper are essential and critical to producing the next generation of lightweight and ultra-strong polymer-based nanocomposite structural materials.

Bamboo-Inspired Renewable, High-Strength, Vibration-Damping Composites for Structural Applications

Renewable structural materials derived from natural biological materials can potentially replace non-renewable synthetic materials for civil engineering and transportation applications. Here, inspired by the functional gradient structure of bamboo, we propose a simple and efficient two-step preparation strategy to convert natural bamboo into a lightweight, high-strength, damping, and sound-insulating structural engineering material called densified bundle-laminated veneer lumber (DBLVL). DBLVL was prepared by finely grading and thinning three layers of bamboo slices and removing the lignin and hemicelluloses from the surface of bamboo bundles. This was followed by penetrating the phenol formaldehyde resin and then solidifying and densifying it in situ. DBLVL had superior mechanical properties due to its bamboo-like gradient laminated structure, three-dimensional network distribution of adhesive under high temperature and high pressure, in situ curing, and solid interfacial bonding. It had a specific tensile strength of 297 MPa cm3 g–1, which was superior to those of many other construction materials. The tensile strength of DBLVL reached 363 MPa, and the bending strength reached 219 MPa, which were 97.28 and 92.11% higher than those of natural bamboo, respectively. The impact toughness reached 15.4 J/cm2. DBLVL also showed excellent damping and vibration reduction (the first three damping ratios were 2.35, 1.81, and 2.40%) and dimensional stability (the thickness expansion rate after 24 h of water absorption was 4.43%). Because of its excellent mechanical properties and hygrothermal stability, DBLVL is expected to replace non-renewable synthetic materials as a green and sustainable structural material for engineering applications.