Lightweight Composites Research Articles

Enhanced thermal and dielectric properties of porous thin films of graphene, conjugated terpolymer of pyrene/thiophene/heptaldehyde, and polyvinylidene difluoride alloys

We have developed conductive, lightweight, and porous composite of polyvinylidene difluoride by blending with synthesized conjugated terpolymer and graphene for conductive polymer composite applications. The new conjugated terpolymer designated as PEPy-TP is synthesized from 3,4-ethylenedioxythiophene, 1-pyrenecarboxzaldehyde, and heptaldehyde through friedel craft reaction. The synthesized terpolymer PEPy-TP have been blended with polyvinylidene difluoride and graphene nanosheets to form porous composite and has been characterized using XRD, TGA, TG-DSC, DTA, DTG, SEM, EDX, and Dielectric spectroscopy. The porous composite is comprised of varying weight percentages of (1, 3, and 5%) of GNS and 10 wt% PEPy-TP in PVDF. The thermal studies on the porous composites indicated that the decomposition occurred at a temperature around 270 and 470 °C corresponds to the PEPy-TP and PVDF/PEPy-TP/GNS (1, 3, and 5%), respectively. The EDX spectrum of neat PEPy-TP polymer and their porous composites of PVDF/PEPy-TP/GNS (1, 3, and 5%) result clearly shows the presence of all elements, such as C, O, S, and F with an atomic weight percentage also. The PVDF/PEPy-TP/5% GNS porous composites having a tremendous electrical conductivity and the dielectric constant value is 56 at 1 MHz and their conductivity of this polymer porous composites value is determined to be 4.9 × 10−6 S/cm at 100 kHz, respectively.

Water absorption behavior of the woven bamboo fabric polypropylene-based composites and their hybrids with glass

The high prone behavior towards water absorption is considered as a major weakness of natural based-fiber composites or bio-composites. These composites can be susceptible to considerable water absorbed due to hydrophilic nature of bamboo fiber, which may affect to degradation of their strength and stiffness performances. The effect of the hybridization is investigated with the study of water immersion at 23 °C and 60 °C, for a period of 70 days. It was shown that the composite’s absorption behavior demonstrated the kinetics behavior and classification proposed by Fick’s theory. There was a 142 % increase in the diffusion coefficients of samples immersed at 60 °C compared to those at 23 °C for BPP composites. The water absorption of BPP composites at 23 °C after 1680 h was approximate of 14.6 %, with the absorption was quite rapid initially, reaching almost 13.01 % after about 720 h. For the hybrid composites of 30B:20G, 20B:35G and 10B:45G for water absorption at 23 °C was reaching almost 10.56 %, 7.30 %, and 2.81 % respectively after 720 h. Furthermore, the composites approached equilibrium faster at 60 °C than at 23 °C. The absorption rate was significantly higher at 60 °C, with 80 % of the total absorption in the first 14 days, while the BPP composites at the immersion of 23 °C, reached equilibrium in the first 30 days. Similar behavior was also observed for the hybrid composites, reached almost 80 % of the total absorption in the first 7 days, when compared with 20 days for the hybrid composites. The presence of external plies of glass effectively decelerates water diffusion into the bamboo polypropylene (BPP) composites. The findings denote a significant observation in which, by substituting few layers of glass with woven-based bamboo in glass-polypropylene composites, offering to a hybrid concept to be possible for developing an alternative, excellent and better performance of light-weight composite.

Ultra-high temperature performance of carbon fiber composite reinforced by HfC nanowires: A promising lightweight composites for aerospace engineering

Lightweight composites with excellent high-temperature performance are attractive as thermal structural components in extreme environment. In general, the excellent properties depend on both their microstructures and intrinsic properties of their counterparts. Herein, we report a lightweight carbon fiber composites reinforced by hafnium carbide nanowires (HfCNWs) and the corresponding high temperature performance. The evolution of the microstructures and compositions after treated at high temperature are analyzed. As suggested from the results, with the presence of HfCNWs, the interlaminar shearing strength (ILSS), out-of plane compression strength (OCS) and flexural strength (FS) increased by 81.36%, 87.96% and 78.38%, respectively. Although the mechanical performance deteriorated after treated at high temperatures, the mechanical strength retention rate (MSR) of HfCNWs reinforced C/C (HfCNWs-C/C) composites is superior to that of pure C/C composites. Besides, the excellent ablative resistance of HfCNWs-C/C composites provide potential possibility to be applied in extreme conditions.

3D printed continuous fiber reinforced composite lightweight structures: A review and outlook

Continuous fiber reinforced composite lightweight structures (CFRSs) are widely applied to aerospace, automobile, marine and other fields due to their high specific strength and modulus, low density and fatigue resistance. Innovations in the additive manufacturing technique of continuous fiber reinforced composites (CFRC) opened new perspectives for the integrated design and fabrication of composite lightweight structures with customized performance and acceptable cost. This paper reviewed the state-of-the-art 3D printing CFRSs and elaborated their future perspectives and potential applications. Specifically, different existing CFRSs printing techniques were reviewed, and the limitations of current processing methods were discussed in details. Then, the CFRSs including 2D and 3D types were discussed in terms of path planning, structural design and optimization methods. Further, the mechanical properties and novel applications in shape morphing and self-monitoring of CFRSs were presented. Finally, this paper concluded with an outlook on future research opportunities on 3D printing CFRSs from design, fabrication to final applications.

Mimicking ‘sea-urchin’ like heirarchical carbon structures self-assembled from carbon fibers for green EMI shielding

Self-assembled structures offer myriad opportunities to explore them for a wide range of applications. Herein, ‘sea-urchin’ like hierarchical structures were obtained from self-assembly of carbon fibers (CF) assisted by refluxing in an acid medium. This unique template-free synthesis of carbon urchins (CU) yields different sizes when the chemical ambiance (pH) around the CF varies. Electromagnetic (EM) pollution has recently gained attention due to the widespread usage of electronics and requires lightweight and reliable solutions to suppress EM interference. Polymer nanocomposite-based shielding serves as an effective solution due to its ability to be tuned as per the commercial requirement. To this end, dispersing flakes of nanoparticles in a polymer matrix has been researched widely but is not amenable to suppressing the EM interference. Herein, the self-assembled structures offer micro-spikes resulting from the sea-urchin-like carbon structure coupled with the incoming field and facilitate the absorption of the EM radiation. The spatial distribution of CU was controlled in different polymeric matrices (thermoplastic, Ethylene vinyl acetate (EVA) and thermoset, epoxy) to realize the potential of these hierarchical structures in EMI shielding applications. The composites with CU show shielding effectiveness (SET) in the range of -45 dB to -52 dB in the X-band, and the green index is close to 1. The shield with the highest SET also showed a quick heat dissipation ability, an added advantage in terms of applicability. Our results begin to suggest that CU can be blended with a wide range of plastics to develop a universal solution in designing lightweight composites for EMI shielding applications.

Hierarchically structured bioinspired nanocomposites.

Next-generation structural materials are expected to be lightweight, high-strength and tough composites with embedded functionalities to sense, adapt, self-repair, morph and restore. This Review highlights recent developments and concepts in bioinspired nanocomposites, emphasizing tailoring of the architecture, interphases and confinement to achieve dynamic and synergetic responses. We highlight cornerstone examples from natural materials with unique mechanical property combinations based on relatively simple building blocks produced in aqueous environments under ambient conditions. A particular focus is on structural hierarchies across multiple length scales to achieve multifunctionality and robustness. We further discuss recent advances, trends and emerging opportunities for combining biological and synthetic components, state-of-the-art characterization and modelling approaches to assess the physical principles underlying nature-inspired design and mechanical responses at multiple length scales. These multidisciplinary approaches promote the synergetic enhancement of individual materials properties and an improved predictive and prescriptive design of the next era of structural materials at multilength scales for a wide range of applications.

Comparison of sawdust bio-composites based on magnesium oxysulfate cement and ordinary Portland cement

This study incorporated sawdust (SD) as a bio-aggregate into magnesium oxysulfate cement (MOSC) and ordinary Portland cement (OPC) for the preparation of composite lightweight materials. The effect of sawdust dosage on the mechanical properties, thermal properties, water absorption, and water resistance of the two bio-composites was investigated. Experimental results revealed that SD-MOSC presented lower density, higher compression strength, and excellent thermal insulation properties than SD-OPC. Thus, MOSC is more suitable as a binder for sawdust aggregates than OPC. Microstructure observation showed that 5 Mg(OH)2·MgSO4·7H2O (5·1·7) phase whiskers preferred to form at the defects of sawdust, indicating that MOSC had better compatibility with sawdust. The increase of sawdust hindered the generation of 5·1·7 phase, resulting in the strength reduction. MOSC-based sawdust bio-composites are a promising material for production of thermal insulation panels and are favorable for environmental protection.

Microstructural evolution, shielding effectiveness, and the ballistic response of Mg/Al7075/B4C/Pb composite produced by combination of coating and severe plastic deformation (SPD) processes

Light-weight metal matrix composites reinforced by Pb and B4C are of interests in aerospace industry due to high strength to weight ratio and excellent shielding effectiveness. This paper investigates microstructure, shielding effectiveness, tensile properties, and high-velocity impact behavior of Mg/Al/B4C/Pb composite. In this composite, the B4C layer was deposited by electrophoretic deposition (EPD) on aluminum layers, then the sandwich with the stacking sequence of Mg/Al/B4C/Pb was fabricated through accumulative roll bonding (ARB). The optical microscopy (OM) and scanning electron microscopy (SEM) images illustrated that by increasing the cycles, all layers within composite experienced instabilities including necking and fracture. In addition, increasing the number of rolling cycles improved tensile properties, namely Young's modulus, elongation, yield, and ultimate strength. Furthermore, according to the results of the high-velocity impact test, by increasing the rolling cycle, less failure such as cracks and perforation was found on surfaces, indicating the enhanced ballistic resistance of composites. Plus, when composites were subjected to electron radiation, less relative doses of radiation were detected by dosimeter at higher rolling cycles which confirmed the attenuation of transmitted rays and then the enhancement of shielding effectiveness of composites.

Tri-Mack demonstrates fast production of thin, lightweight thermoplastic composites

Tri-Mack Plastics Manufacturing Corporation, a high-performance thermoplastics parts manufacturer, announced their latest product-development at CAMX show: very lightweight, high-strength enclosures made from just eight plies of unidirectional carbon-fiber reinforced thermoplastic composite (TPC) tape and only forty thousandths of an inch thick (.040″).

Correlating multi-scale structure characteristics to mechanical behavior of Caprinae horn sheaths

Horns are used by Bovidae animals for intraspecific combat; as such they are among Nature's toughest materials that require resistance to extreme loads. As a typical subfamily among Bovidae, Caprinae own light-wight horn with balanced strength and toughness. However, their structure and the salient mechanisms that underlie their mechanical behavior remain uncertain. This work clarifies the effect of multi-scale structure characteristics on mechanical behaviors of horn sheath by comparing Cashmere goat, White goat and Black sheep. With the methods of fractographic observations, conformational analysis, acoustic emission and finite element methods. Conformation of keratin and strength of fibre were proposed to influence the tensile/flexural performance a lot under both dried and hydrated condition. The corrugated lamellae structure was assumed to promote crack deflection and enhance dried samples, which showed more advantageous for applications of flexural loading. It is hard to impute the difference of mechanics to any one factor, and the synergism of multi-scale mechanisms is important to mechanical properties in Caprinae horn sheath. This research is expected to further encourage the horn-inspired design of secondary load-carrying lightweight composites.

Flexible and lightweight Kevlar composites towards flame retardant and impact resistance with excellent thermal stability

The impact and thermal damage in extreme environments generally exist together. In this context, the design of safety protection materials ought to consider not only the single impact protection performance, but also thermal stability and flame resistance. In order to simultaneously achieve the impact resistance, thermal stability and flame resistance properties, a flexible and lightweight shear-hardened composite material (STF/Kevlar) was prepared by impregnating and drying shear thickening fluid (STF) on Kevlar fabric. Due to the favorable shear thickening performance of shear thickening fluid, STF/Kevlar composite material can increase the maximum yarn pull-out force of the fabric yarn from 3.3 N to 16.3 N with the impregnation weight gain of 55 wt%. Moreover, in bullet impact experiment, a single layer of STF/Kevlar fabric can nearly double the time it takes a bullet to penetrate pure Kevlar fabric. Additionally, STF/Kevlar composite material exhibits significant flame resistance as well. The limit oxygen index can reach 32 %, and after 30 min high temperature treatment at 400 °C, the composite still maintains good mechanical property and flexibility. This multi-functional composite material along with the performance of resisting both mechanical shock and thermal damage in extreme environments is expected to broadly apply in the field of lightweight protection.

Novel Battery Module Design for Increased Resource Efficiency

The work presented focuses on a material efficient, modular design of a battery module for vehicle applications. Furthermore, the possibility of disassembly of individual components was considered. The constructive design focused on the combination of cast aluminum components, lightweight composites panels, and aluminum-foam phase-change material (PCM) composites. This led to an innovative battery module, which was finally implemented on a demonstrator level. The required cooling power of the module could be reduced by approx. 20% compared to conventional battery module setups. Furthermore, the constructive design of the module and the use of a “debonding-on-demand” technology enabled significantly faster disassembly. Die to the combination of these advantages and the possibility to give individual parts of the module a second life for new modules, the module shows a high resource efficiency as well as high CO2 savings potential.

Recent Advances and Reliable Assessment of Solid‐State Materials for Hydrogen Storage: A Step Forward toward a Sustainable H2 Economy

AbstractThe hydrogen economy is an envisaged system proposed for a sustainable energy future that comprises hydrogen production, storage, transportation, and stationary/mobile applications. Recently, research efforts are devoted to build a H2 economy; however, the reduced hydrogen volumetric density hinders the effective hydrogen storage. To combat this, material‐based hydrogen storage is an emerging trend that has the potential to meet the ongoing goals of the United States Department of Energy. Herein, a critical review is presented on the state‐of‐the‐art material‐based hydrogen storage where nanostructured engineering and nanotechnology have driven a rapid growth in material design from physical sorbents (carbons, metal‐organic frameworks, and organic polymer frameworks) to chemical sorbents (complex and metal nanohydrides). The research trends in physical sorption include tailoring the textural features of porous materials and enhancing the binding energy strength by inducing hydrogen spill‐over effect and functionalization of surfaces. For chemical hydrogen storage, strategies are presented to ameliorate the sorption kinetics and thermodynamics using reactive hydrides, lightweight composites, and nanoconfinement of hydrides. Considering the long‐term hydrogen storage, the concept of para hydrogen storage is also highlighted. Finally, the challenges and their plausible solutions are discussed to attain a sustainable hydrogen economy, in the near future.

A multi-scale model to predict the electromagetic interference shielding performance of (Fe/Cu)@CNT/SA/PDMS flexible composite

(Fe/Cu)@CNT/SA/PDMS flexible composites are prepared by vacuum infiltrating PDMS into CNT/SA aerogel with Fe and Cu bimetallic nanoparticles coated on tubes. The dielectric loss and magnetic loss capacity of the composite are effectively improved by the coated Fe and Cu bimetallic nanoparticles. In addition, CNTs in the aerogel skeleton connected to each other to form a stable conductive network, leading to a nice conductivity and shielding stability under certain strain. More importantly, a multi-scale model based on propagation matrix method are developed. Based on the introduced model, the EMI-SE values of the composite are calculated and the internal mechanisms are analyzed. Results shown that the EMI-SE values of the composite can be further improved more than 90 dB. These light-weight composites with good flexibility and stable EMI-SE have a wide range of application prospects.

Preparation of carbon fiber-reinforced SiC ceramics by stereolithography and secondary silicon infiltration

Stereolithography is an extremely effective three-dimensional (3D) printing technology for the rapid fabrication of high-precision, complex-shaped, and large-scale SiC-based ceramic composites. The combination of photopolymerization-based additive manufacturing and liquid silicon infiltration (LSI) process has been widely used for fabricating lightweight and high-strength carbon fiber-reinforced SiC (Cf/SiC) ceramic matrix composites. However, the fracture toughness of Cf/SiC ceramics prepared by LSI is generally low due to the erosion of carbon fibers by liquid silicon. In this study, we propose a novel fabrication route for Cf/SiC composites by introducing SiC-protected carbon fibers in the photosensitive SiC slurry to prevent the erosion of carbon fibers during the LSI. The fracture toughness of the composites is significantly improved due to the addition of carbon fibers, and it is also much better than the previously reported value for Cf/SiC ceramics. Overall, this study provides an effective strategy for the refined and mass production of ceramic matrix composites.

Compressive Properties of Poly (Dimethylsiloxane)–Hollow Glass Microballoons Syntactic Foams

Polymer syntactic foams are lightweight polymer composites that are prepared by introducing hollow microspheres in a resin. The main endeavour is to obtain a significant reduction in the weight of the composite along with energy absorption. The present investigation aims to prepare poly (dimethylsiloxane) (PDMS)-hollow glass microballoons (HGM) (40–60% v/v) syntactic foams. Not only did HGM reduce the density of the syntactic foams but also act as a reinforcing phase and increase the compressive properties of PDMS. A ∼25% reduction in density was obtained in syntactic foam when compared to the neat elastomer. Similarly, an improvement of ∼118% in compressive strength was attained at 40% loading of HGM in PDMS. Specific compressive strength and toughness values also registered improvements of the order of ∼191 and ∼240% respectively which highlight the potential of PDMS syntactic foams in varied applications.

Damping analysis of stiffened laminated composite plates in thermal environment

High-strength and lightweight composites used in high-speed vehicles and aircraft experience increased temperature owing to aerodynamic friction. Because of the rise in temperature, the elastic moduli of the composites are degraded and inherent viscous damping is increased to the glass transition temperature. In this work, the damping performance of unstiffened and stiffened polyetheretherketone (PEEK) based intermediate modulus (IM7) carbon fiber laminated composite plates is evaluated at various temperatures using displacement- and energy-based approaches. In the displacement-based approach, the logarithmic decrement of the damped vibration is determined to investigate the effect of lamina sequences, stiffener orientation, and stiffener depth at different temperatures. A first-order shear deformation theory considering the viscoelastic property of the composite lamina is implemented to simulate the damped dynamic response of the laminated composite plates in a thermal environment. The best suitable damping model, among Rayleigh damping and modal expansion damping, has been identified to evaluate the damping matrix. Furthermore, the energy-based damping analysis appeared to be a robust approach to evaluate the damping performance as compared to the displacement-based analysis. It is concluded that stiffened plates effectively suppress the dynamic response at elevated temperature, whereas the unstiffened plates show relatively better damping performance at lower temperature.

Lightweight polyester composites via nanoreinforced syntactic foams

Syntactic foams and their reinforcement with cellulose nanocrystals (CNC) in a thermosetting polyester resin (PR) matrix were studied in order to provide a pathway for lightweight composites for automotive applications with enhanced performance including thermomechanical properties and water uptake. A novel method for coating hollow glass spheres (HGS) with CNC was developed. Various combinations of functionalized CNC and surface modified HGS were studied to determine interactions between the two materials. Surface analysis techniques indicated that CNC were successfully deposited onto the HGS surface and remained at the surface after compounding with PR. Dynamic mechanical analysis of composites samples indicated a 30% increase in high temperature storage modulus between CNC coated HGS samples and uncoated HGS samples. Shifts in tan(δ) peak intensity and beta-relaxation temperature also indicated an increase in interphase volume around CNC coated HGS as compared to uncoated HGS samples. Coating HGS with CNC reduced the maximum water adsorption by as much as 40% indicating the potential for this material system in high moisture environments.

A Review on Analysis of Reinforced Recycled Rubber Composites

Rubber recycling attracts considerable attention by a variety of industries around the world due to shrinking resources, increasing cost of raw materials, growing awareness of sustainable development, and environmental issues. Recycled rubber is commonly used in aeronautic, automotive, and transportation industries. In this study, recycled rubber composites designed with different reinforcements in the literature are scrutinized by means of toughening mechanisms, mechanical and physical properties, as well as microstructural and fracture surface analysis. Microscale reinforcements (glass bubbles, alumina fiber, etc.) and nanoscale reinforcements (nanosilica, graphene nanoplatelets, etc.) utilized as reinforcements in rubber composites are thoroughly reviewed. The general mechanical properties reported by previous studies, such as tensile, compressive, and flexural strength, are investigated with the main goal of optimizing the amount of reinforcement used. The majority of the studies on recycled rubber composites show that recycled rubber reinforced with microscale particles leads to the development of physical and mechanical properties of the structures and also provides low-cost and lightweight composites for several application areas. Moreover, recycled rubber containing composites can be suitable for applications where high toughness and high resistance to impact are desirable. The present review aims to demonstrate research on reinforced recycled rubber composites in the literature and prospective outcomes.

Using low-grade calcined clay to develop low-carbon and lightweight strain-hardening cement composites

The paper reports the use of low-grade calcined clay (LCC), a waste clay from construction and excavation works, to produce low-carbon and lightweight strain-hardening cement composites (SHCC). The influence of LCC content (20, 40 and 60% by mass) on the hydration, microstructure, strength, ductility, shrinkage and embodied carbon of SHCC has been investigated. Pozzolanic reaction between LCC and cement hydration products has been observed, which results in significant pore refinement at 20% and 40% cement replacement. The density of SHCC containing LCC was only around 1600 kg/m3. The compressive strength, tensile strain, and tensile strength of SHCC mixtures containing 20% LCC were improved by 3.21%, 22.10%, and 32.28%, respectively. A continued increase in LCC substitution caused a decrease in the strength by the agglomeration of LCC and insufficient calcium hydroxide supply. Furthermore, a significant reduction in embodied carbon was achieved by replacing cement with LCC. Overall, this study shows that low-grade calcined clay has a high potential in producing low-carbon and lightweight SHCC.