Advanced Composites Research Articles

Nanocomposites for Aircraft Applications

The steady increase in jet fuel prices in recent years has accelerated the quest for greater economy in airline operations. While improvements in aerodynamic efficiency, engine fuel efficiency, etc., have been sought, lighter and stronger materials for aircraft structural components remain a very important goal. The percentage of advanced composites, utilizing carbon fibers, in modern aircraft has reached 50 percent. The trend now is to use nano reinforcements such as graphene and carbon nanotubes to further reduce the structural weight. Due to the difficulties in fabricating nanocomposites with a high enough volume fraction of nano reinforcement, the nano reinforcements are either added to the polymer matrix or grown on the carbon fibers. The nano reinforcements are multi-functional; thus, in addition to contributing strength, they contribute to other properties such as electrical conductivity which in turn enhances the lightning strike protection, electrostatic discharge, electromagnetic shielding, etc. This paper summarizes these aspects and also describes the applications of nanocomposites in aircraft interiors, brake components, aircraft repair, etc.

An Intelligent Manufacturing Platform of Polymers: Polymeric Material Genome Engineering

Polymeric materials with excellent performance are the foundation for developing high-level technology and advanced manufacturing. Polymeric material genome engineering (PMGE) is becoming a vital platform for the intelligent manufacturing of polymeric materials. However, the development of PMGE is still in its infancy, and many issues remain to be addressed. In this perspective, we elaborate on the PMGE concepts, summarize the state-of-the-art research and achievements, and highlight the challenges and prospects in this field. In particular, we focus on property estimation approaches, including property proxy prediction and machine learning prediction of polymer properties. The potential engineering applications of PMGE are discussed, including the fields of advanced composites, polymeric materials for communications, and integrated circuits.

Structural integrity and healing efficiency study of micro-capsule based composite materials via 1H NMR relaxometry

In this work we present a novel approach utilizing nuclear magnetic resonance (NMR) relaxometry to assess the structural stability of microcapsules employed as self-healing agents in advanced aerospace composites both in ambient and harsh environmental conditions. We successfully correlate the amount of the encapsulated self-healing agent with the signal intensity and confirm non-destructively the quantity of the encapsulated self-healing agent mass for the first time in the literature using 1H NMR spin–spin relaxation techniques on urea–formaldehyde (UF) microcapsules of different diameters containing an epoxy healing agent. The amount of self-healing agent is shown to increase by reducing the capsule diameter; however, the reduced shell mass renders the capsules more fragile and prone to failure. Most notably, via NMR experiments conducted during thermal cycling simulating flight conditions, we demonstrate that the microcapsule integrity under thermal fatigue varies according to their size. Especially we experimentally verify that the microcapsules with the most sensitive shells are the 147 nm and 133 nm diameter microcapsules, which are the most commonly used in self-healing systems. Finally, we were able to retrieve the same results using a portable NMR spectrometer developed in-house for in situ microcapsule testing, thus demonstrating the potential of NMR relaxometry as a powerful non-destructive evaluation tool for the microcapsule production line.

Investigating microstructural and mechanical behavior of stir-squeeze cast TiO2–SiC/Al6082 bimodal hybrid composites

Greater advantages of employing hybrid reinforced advanced aluminum matrix composites over single particle reinforced composites have been the highlights of recent times. Herein, Al6082 bimodal hybrid composites embedded with different proportions of SiC and TiO2 particles were fabricated via modified stir-squeeze cast technique. A transmission electron microscopy was used for morphological evaluation of TiO2 particles while microstructure of fabricated composites and fractured surfaces were analyzed by using field emission scanning electron microscopy. Energy dispersive X-ray spectroscopy was used for evaluation of elements and phase analysis was done by using X-ray diffraction technique. Microstructural analysis confirms the homogeneous dispersion of SiC particles up to 3 wt.% and beyond that, clusters of SiC were observed which deteriorates the properties of composites. Maximum enhancement in mechanical properties of Al6082 alloy was noticed for incorporation of 3 wt.% of SiC and 0.5 wt.% of TiO2. 0.5 wt.%TiO2-3 wt.% SiC reinforced Al6082 composites enhanced yield strength, Ultimate tensile strength, and compressive strength by 215.84 ± 1.43 MPa, 268.84 ± 1.75 Mpa and 321.42 MPa, respectively, over as-cast Al6082 alloy.

Toughening additive manufactured Zr-based bulk metallic glass composites by martensite phase transformation

Additive manufacturing technology based on laser powder bed fusion (LPBF) offers a novel approach for fabricating bulk metallic glass (BMG) products without restriction in size and geometry. Nevertheless, the BMGs prepared by LPBF usually suffered from less plasticity and poorer fracture toughness as compared to their cast counterparts due to partial crystallization in heat-affected zones (HAZs). Since crystallization in HAZs is hard to avoid completely in LPBF BMGs, it is desirable to design a suitable alloy system, in which only ductile crystalline phase, instead of brittle intermetallics, is formed in HAZs. This unique structure could effectively increase the toughness/plasticity of the LPBF BMGs. To achieve this goal, a quaternary BMG system with a composition of Zr47.5Cu45.5Al5Co2 is adopted and subjected to LPBF. It is found that nearly a single phase of B2-ZrCu is precipitated in HAZs, while a fully amorphous phase is formed in molten pools (MPs). This B2 phase reinforced BMG composite exhibits excellent mechanical properties with enhanced plasticity and toughness. Furthermore, it is easy to modulate the mechanical properties by altering the amount of the B2 phase via adjusting the laser energy input. Finally, the best combination of strength, plasticity, and notch toughness is obtained in the BMG composite containing 27.4% B2 phase and 72.6% amorphous phase, which exhibits yield strength (σs) of 1423 MPa, plastic strain (εp) of 4.65%, and notch toughness (Kq) of 53.9 MPa m1/2. Furthermore, a notable strain-hardening is also observed. The improvement of plasticity/toughness and appearance of strain-hardening behavior are mainly due to the martensite phase transformation from the B2 phase to the Cm phase during plastic deformation (i.e., the phase transformation-induced plasticity effect). The current work provides a guide for making advanced BMGs and BMG composites by additive manufacturing.

A molecularly engineered bioderived polyphosphonate containing Schiff base towards fire-retardant PLA with enhanced crystallinity and mechanical properties

To expand the practical application and realize sustainable development, it is urgent to develop advanced polylactide composites with fire retardancy and mechanically strong properties by utilizing bio-derived additives. Unfortunately, such desired performance portfolio is still unsatisfactory due to unclear mechanism and improper design strategy. In this paper, a novel bio-derived polyphosphonate containing Schiff base (PVP) was prepared by a two-step method of condensation and addition reactions. By incorporating only 0.5 wt% PVP, the LOI value of PLA is increased to 32.5 vol% as well as achieving a UL-94 V-0 rating. Such superior fire retardancy is ascribed to the physical barrier effect of char residue, which arising from the cyclization of Schiff base and catalytic carbonization of polyphosphonate. Due to the crosslinking reaction between PLA and PVP and nucleating effect of PVP in the PLA matrix, the mechanical strength of PLA is increased by 10.2% with addition of 1.0 wt% PVP. This study provides a feasible way for designing bio-derived fire retardants to simultaneously improving the fire retardancy and mechanical strength of PLA, thus is expected to expand the practical application of PLA materials.

Superlubricity of Materials: Progress, Potential, and Challenges.

This review paper provides a comprehensive overview of the phenomenon of superlubricity, its associated material characteristics, and its potential applications. Superlubricity, the state of near-zero friction between two surfaces, presents significant potential for enhancing the efficiency of mechanical systems, thus attracting significant attention in both academic and industrial realms. We explore the atomic/molecular structures that enable this characteristic and discuss notable superlubric materials, including graphite, diamond-like carbon, and advanced engineering composites. The review further elaborates on the methods of achieving superlubricity at both nanoscale and macroscale levels, highlighting the influence of environmental conditions. We also discuss superlubricity's applications, ranging from mechanical systems to energy conservation and biomedical applications. Despite the promising potential, the realization of superlubricity is laden with challenges. We address these technical difficulties, specifically those related to achieving and maintaining superlubricity, and the issues encountered in scaling up for industrial applications. The paper also underscores the sustainability concerns associated with superlubricity and proposes potential solutions. We conclude with a discussion of the possible future research directions and the impact of technological innovations in this field. This review thus provides a valuable resource for researchers and industry professionals engaged in the development and application of superlubric materials.

Metal-Free Hybrid Energetic Composites Based on Donor-Acceptor π-Conjugated Organic Energetic Catalysts with Enlightening the Laser Ignition Performance of Multi-Scale Ammonium Perchlorate.

Photosensitive materials, such as energetic complexes, usually have high sensitivity and cause heavy-metal pollution, whereas others, like carbon black and dye, do not contain energy, which affects energy output and mechanical properties. In this work, donor-acceptor π-conjugated energetic catalysts, denoted as D-n, are designed and synthesized. Nonmetallic hybrid energetic composites are prepared by assembling the as-synthesized catalysts into multiscale ammonium perchlorate (AP). Composites containing catalysts and APs can be successfully ignited without the involvement of metals. The new ignition mechanism is further analyzed using experimental and theoretical analyses such as UV-vis-near-infrared (NIR) spectra, electron-spin resonance spectroscopy, and energy-gap analysis. The shortest ignition delay time is 56ms under the experimental condition of a NIR wavelength of 1064nm and a laser power of 10W. At the voltage of 1kV and the electric field of 500V mm-1 , the laser-ignition delay time of D-2/AP hybrid composite decreases from 56 to 35ms because D-2 also exhibits organic semiconductor-like properties. D-2/AP and D-12/AP can also be used to successfully laser ignite other common energetic materials. This study can guide the development of advanced metal-free laser-ignitable energetic composites to address challenges in the field of aerospace engineering.

Damage Prediction of Buckled Composite Single Stiffened Panel Subject to Static Compression

The initial flaws in laminated composite structures are susceptible to inter-/intraply damage. Progressive damage analysis tools help the understanding of the mechanisms for damage initiation and growth while assisting in the design, analysis, and sustainment methods. The global–local modeling approach for the single-stringer postbuckled panel evaluated in this effort used Teflon inserts to provide initial “cracks” for model validation. The effort aimed to develop, evaluate, and enhance methods to predict damage initiation, progression, and failure of postbuckled composite hat-stiffened panels using the commercially available software Abaqus. Three methods were considered: the virtual crack closure technique (VCCT), the cohesive zone model (CZM), and enhanced Schapery theory (EST). The VCCT and CZM successfully predicted multiple delaminations. EST works with the CZM to capture delamination and facilitate interactions between interlaminar and intralaminar failures. When comparing the damage morphology against the experimental data produced through the NASA Advanced Composites Project, the present models captured the delamination, matrix, and fiber damage patterns. The VCCT and EST predictions were within 2% of the experimental peak load.

Overview of biomass valorization: Case study of nanocarbons, biofuels and their derivatives

With the increasing awareness of the serious pollution from the usage of fossil fuels and the fast advances of technologies, the usage of biomass has been increased significantly. In this review paper, the biomass serving as carbon precursors and the energy has been reviewed including lotus lives, wheat flour, fish scale, fish skin, wax gourd, etc. The formed carbon nanostructures are reviewed together with their applications including the treatment volatile organic compounds (VOCs), heavy metal ions from polluted water, spilled oil, fillers for advanced composites, etc. This paper gives the usage of biomass in a sustainable and green way.

Caffeine-treated wood as an innovative filler for advanced polymer composites

Polymer composites, based on the wood flour originating from an invasive black cherry (Prunus serotina Ehrh.) treated with caffeine to achieve increased bio-resistance, were obtained in this study. The caffeine-treated wood had a significant effect on the supermolecular structure of polymer matrix, resulting in a high content of polymorphic β-PP phase, as well as an increase in nucleation activity of wood surface. The caffeine treatment of wood was an effective method of achieving increased resistance of composites to selected fungi and bacteria while maintaining good mechanical strength and thermal resistance. Addition of black cherry wood to polymer matrix induced inhibition of the release of volatile organic compounds. Increased resistance to fungi and bacteria depended on formation a significant amount of the β-phase up to 35% in the composite with 30% of caffeine-treated wooden filler and a simultaneous decrease in crystallinity from 52% for pure PP to 45% for mentioned composite.

Recent Advances and Perspectives Regarding Paper-Based Sensors for Salivary Biomarker Detection

Paper-based sensors overcome the drawbacks of conventional sensors in terms of their flexibility, portability, and stability compared to conventional sensors. Moreover, as a noninvasive bodily fluid, saliva contains various biomarkers related to physical status, which makes it perfectly matched with to use of paper-based sensors to manufacture a convenient and inexpensive disposable sensing device. This review focuses on the recent advances and progress in the design of paper-based salivary sensors and their applications. The first part mainly discusses various paper-based sensors and their advanced compositions, including dipstick assay, lateral flow assay, and microfluidic analytical device. Different detection methods in salivary biomarker detection are specially introduced in the secondary section, then their multiple potential applications and prospects are summarized. The sensor has excellent advantages for saliva detection, provides a reliable platform for point-of-care tests and telemedicine, and epically promotes the development of the medical Internet of Things.

Solar Cycle Variation of 0.3–1.29 MeV Nucleon−1 Heavy Ion Composition During Quiet Times Near 1 au in Solar Cycles 23 and 24

We report on the annual variation of quiet-time suprathermal ion composition for C through Fe using Advanced Composition Explorer (ACE)/Ultra-Low Energy Isotope Spectrometer data over the energy range 0.3–1.28 MeV nuc−1 from 1998 through 2019, covering solar cycle 23's rising phase through Solar Cycle 24's declining phase. Our findings are: (1) quiet-time suprathermal abundances resemble CIR-associated particles during solar minima; (2) quiet-time suprathermals are M/Q fractionated in a manner that is consistent with M/Q fractionation in large gradual solar energetic particle events (GSEP) during solar maxima; and (3) variability within the quiet-time suprathermal pool increases as a function of M/Q and is consistent with the analogous variability in GSEP events. From these observations, we infer that quiet-time suprathermal ions are remnants of CIRs in solar minima and GSEP events in solar maxima. Coincident with these results, we also unexpectedly show that S behaves like a low FIP ion in the suprathermal regime, and is therefore drawn from low FIP solar sources.

Distributions of Mesoscale Periodic Structures in the Elemental and Ionic Composition of the Solar Wind

Multiple statistical and event studies based on in situ observations have shown that the solar wind contains mesoscale (∼ 100 – 10,000 Mm) periodic structures in the proton number density. Remote observations of such structures and event studies of concurrent variations in composition have demonstrated that they can form in the solar atmosphere and be preserved while advecting outwards through the heliosphere. Viall, Kepko, and Spence (J. Geophys. Res. (Space Phys.)113, A07101, 2008; J. Geophys. Res. (Space Phys.)114, A01201, 2009) and Kepko, Viall, and Wolfinger (J. Geophys. Res. (Space Phys.)125(8), e28037, 2020) have reported that periodic proton density structures preferentially occur at specific radial length scales and have published their distributions from Wind measurements near L1. Here, we conduct a statistical study of 14 years (1998 – 2011) of 12-minute composition data measured by the Solar Wind Ion Composition Spectrometer instrument aboard the Advanced Composition Explorer spacecraft. We found that the elemental and ionic composition also contain statistically significant mesoscale periodic structures and, for the first time, present occurrence distributions for elemental abundance ratios with low, intermediate, and high first ionization potentials as well as for key solar wind charge states. These distributions set important constraints on solar wind formation in general and the formation of periodic mesoscale solar wind structures specifically, as the elemental and ionic composition are known to be determined at the Sun and to not evolve during advection.

Nanoparticles Surface Energy Effect on Mechanical Properties and Microscopic Deformation of 3D Heterogeneous Nanostructures

Nanoparticle-contained graphene foam material has attracted many practical applications in recent years, which require an in-depth comprehension of the basic mechanics of these heterogenous materials. In this paper, the effect of nanoparticles surface energy on the mechanical properties of nanoparticle-filled graphene foam under uniaxial tension and compression is systematically studied by the coarse-grained molecular dynamics simulation method. The mechanical strength of these nanoparticle-filled graphene foam is directly influenced by tuning the nanoparticles surface energy. The varying peeling-off behaviors of graphene sheets influenced by the surface energy of nanoparticles are observed. The stress distribution under uniaxial compression and tension at different nanoparticles surface energy is also studied. The mechanical behavior of nanoparticle-filled graphene foam is directly dependent on nanoparticles surface energy. The results should be helpful not only to understand the micro mechanism of such nanomaterials, but also to the design of advanced composites and devices based on porous materials mixed with particles.

Mapping of multimodality data for manufacturing analyses in automated fiber placement

Automated Fiber Placement (AFP) is an advanced composites manufacturing technique utilized for industrial scale structures. During this process, data is collected from a multitude of modalities spanning numerical analysis of processing parameters to inspection techniques. With data collection existing both in-situ and ex-situ. To ensure interoperability of multimodality data, a mapping is necessary to understand the relationship between these various conditions, and the positioning on the tool surface. This paper defines a mapping technique which enables the evaluation of spatial data from many different sources within the AFP process. Through these mapping techniques, a global array of data is generated that includes all aspects of AFP manufacturing. The developed methodologies are applied to the manufacturing of a doubly curved part. Results showcase the ability to map multimodality data into a uniform format. With the uniform format of the data, further steps can be made to the improvement of fiber paths and processing parameters.

A versatile and highly efficient algorithm to generate representative microstructures for heterogeneous materials

In this study, a novel approach based on the maximum penetration-biased (MPB) algorithm is proposed to rapidly generate representative volume elements (RVEs) for advanced composites. This method is capable of handling various microstructural features such as nonuniform distribution of high-volume fractions, concave or convex inclusions and the control of inter-inclusion distances. Statistical functions from short-range to long-range demonstrate that the resulting microstructures are complete spatial random, and the microstructures observed in realistic composites can be reproduced by the proposed algorithm. Accurate prediction for the elastic properties and transverse isotropy of the generated microstructures with varying inclusion shapes using homogenization method further verify the validity of the developed method. A nonlinear damage study compared to the circular inclusion reveals that the capsule shape leads to a reduction of strength of unidirectional fiber reinforced composites under transverse tension or compression while the lobular inclusion presents a deterioration of strength under tension but an enhancement of strength in compression. The MPB algorithm provides an effective tool for micromechanical assessment, quantitative research and data-driven studies such as machine learning of composites.

Glass Fiber-Epoxy Composites with Carbon Nanotube Fillers for Enhancing Properties in Structure Modeling and Analysis Using Artificial Intelligence Technique.

Hybrid composite materials are a form of material that incorporates more than one type of reinforcement into a matrix to attain enhanced qualities. This usually includes the use of nanoparticle fillers in classic advanced composites with fiber reinforcements such as carbon or glass. In the current investigation, the impact of carbon nanopowder filler on the wear and thermal performance of the chopped strand mat E-glass fiber-reinforced epoxy composite (GFREC) were analyzed. Multiwall carbon nanotube (MWCNT) fillers were used; they react with the resin system to contribute a significant improvement of properties in the polymer cross-linking web. The experiments were carried out employing the central composite method of design of experiment (DOE). A polynomial mathematical model was created using response surface methodology (RSM). To forecast the wear rate of composites, four machine learning (ML) regression models were built. The study's findings indicate that the addition of carbon nanopowder has a substantial impact on the wear behavior of composites. This is mostly owing to the homogeneity created by the carbon nanofillers in uniformly dispersing the reinforcements in the matrix phase. Results revealed that a load of 1.005 kg, a sliding velocity of 1.499 m/s, a sliding distance of 150 m, and 15 wt % of filler were found to be the optimal parameters for the efficient reduction of specific wear rate. Composites with 10 and 20% carbon contents exhibit lower thermal expansion coefficients than plain composites. These composites' coefficients of thermal expansion fell by 45 and 9%, respectively. If the carbon proportion increases beyond 20%, so will the thermal coefficient of expansion.

Effect of neutron irradiation on tensile properties of advanced Cu-based alloys and composites developed for fusion applications

The effect of neutron irradiation on tensile properties and fracture mode has been investigated for several advanced CuCrZr alloys in the frame of the European fusion material development program. Five material grades utilizing different strengthening principles have been exposed to neutron irradiation up to ∼2.5 dpa (displacement per atom) in the target operational temperature range of 150–450 °C. The strengthening mechanisms are based on the application of: i) tungsten particles; ii) tungsten foils (laminate structure); iii) tungsten fibers; iv) Y2O3 particles; v) vanadium addition (0.22%). Neutron irradiation was performed in the BR2 material test reactor inside the fuel channel in order to maximize the fast neutron flux. The upper irradiation temperature of 450 °C was selected to validate the ability of the pre-selected advanced grades to sustain the high temperature irradiation, since the baseline ITER specification CuCrZr is known not to retain sufficient tensile strength above 400 °C in non-irradiated conditions and shows strong irradiation induced softening above 300 °C. Neutron irradiation at 150 °C caused severe embrittlement of tungsten-copper laminates as well as a considerable reduction of the total elongation of all other grades. The irradiation at 450 °C led to the reduction of the yield strength and ultimate tensile strength (i.e. irradiation softening) in the vanadium-doped alloy similar to CuCrZr, while all other materials preserved or increased their strength (irradiation hardening). The fracture surfaces of the tested samples were analysed to investigate the modification of the deformation mechanisms in each particular case.

Enhanced removal of Cu(II) ions from aqueous solution by in-situ synthesis of zeolitic imidazolate framework-67@wood aerogel composite adsorbent

ABSTRACT Zeolitic imidazolate frameworks (ZIFs) were considered to be one of the most promising emerging nanoporous adsorbents capable of efficiently removing a variety of heavy metals ions from wastewater. However, due to the powdered crystalline state, easy aggregation and instability of ZIFs materials, their actual large-scale applications in water matrices are significantly hindered. Compounding ZIFs with self-supporting porous wood aerogel (WA) to obtain advanced composites is excepted to further enhance their adsorption performance with higher practicability. Herein, a novel Zeolitic Imidazolate Framework-67 (ZIF-67)@wood aerogel (denoted as ZIF-67@WA) adsorbent for efficient capture of Cu(II) ions was successfully fabricated via in situ growth of Cobalt-based ZIF-67 particles onto the WA scaffold. Benefiting from the integration of unique three-dimensional porous structures and abundant accessible active sites, the obtained ZIF-67@WA hybrids exhibited fast adsorption kinetics and the maximum adsorption capacity towards Cu(II) calculated from the Langmuir model was 254.84 mg g−1. The adsorption kinetic and isotherm studies were consistent with pseudo-second-order model (R 2 = 0.991) and Langmuir model (R 2 = 0.973), indicating the adsorption of Cu(II) was a monolayer chemisorption process. This work proposed a new route for designing and constructing functionalized MOF@biomass hybrid materials for heavy metal wastewater treatment.