High-performance Composites Research Articles

Experimental investigation on mechanical properties and fire performance of innovative wheat straw-gypsum composites as building sheathing panels

An innovative and high-performance wheat straw-gypsum composite (SGC) was developed to solve the problem of cracking and separation caused by water release when exposed to high temperature of gypsum board (GB) on the fire side of a wall. Compatibility between wheat straw and gypsum crystal was improved by combined pretreatment (i.e., sodium hydroxide and coupling agent) and adding magnesite. The mechanical properties of SGC were investigated and its fire performance determined by cone calorimetry and fire tests. The results indicated that the modulus of rupture, modulus of elasticity, and internal bond strength of SGC were 53.7%, 115.9%, and 173.9%, respectively higher than the traditional GB. The improvement in strength was attributed to the fact that alkali-treated wheat straw was well combined with gypsum crystals through magnesite to form a compact structure, as evidenced by scanning electron microscopy. SGC had extremely low heat and smoke release rate, ignition point at > 1200 s, and mass retention increased by 17.1%, compared with the literature results of gypsum-based bio-composites. Under a 60-min duration exposure, the charring depth of the wood studs of light frame walls sheathed with GB was 27 mm higher than that of SGC wall, and the bearing capacity retention rate of SGC wall 65.4%, while that of GB wall was lost. Errors between the calculation of bearing capacity proposed in this study and test values were < 6%. SGC with superior thermal insulation and mechanical properties could beneficially replace GB as fire-resistant panels in buildings.

UHMWPE fibers reinforced gradient structure to break the thermal-dielectric-mechanical trade-off in high filled polyethylene

In view of the diversified demands for thermal management materials in soaring developments of electrical systems, the high thermally conductive composites often suffer from their poor mechanical properties and electrical insulation. Targeting at enhancing simultaneous thermal conductivity, dielectric and mechanical properties, the fibers reinforced gradient structured polyethylene-based composites consisting of ultrahigh molecular weight polyethylene (UHMWPE) fiber layer and hybrid-filled layer are proposed and successfully prepared by simple overlapping-hot pressing. The fibers collaborated with gradient arrangement of hybrid-filled layer in modulating the temperature, electric and stress field distribution. The resultant as-designed composites exhibit excellent thermal conductivity of 0.91 W/(m·K), ultrahigh tensile strength of 104.7 MPa and superior breakdown strength of 161.5 kV/mm, which are increased by 18%, 1374% and 37% than those of the homogeneous composites, respectively. This work provides a new strategy for manufacturing high-performance polymer-based composites.

UV-Curing Assisted Direct Ink Writing of Dense, Crack-Free, and High-Performance Zirconia-Based Composites With Aligned Alumina Platelets.

Additive manufacturing (AM) of high-performance structural ceramic components with comparative strength and toughness as conventionally manufactured ceramics remains challenging. Here, a UV-curing approach is integrated in direct ink writing (DIW), taking advantage from DIW to enable an easy use of high solid-loading pastes and multi-layered materials with compositional changes; while, avoiding drying problems. UV-curable opaque zirconia-based slurries with a solid loading of 51 vol% are developed to fabricate dense and crack-free alumina-toughened zirconia (ATZ) containing 3 wt% alumina platelets. Importantly, a non-reactive diluent is added to relieve polymerization-induced internal stresses, avoid subsequent warping and cracking, and facilitate the de-binding. For the first time, UV-curing assisted DIW-printed ceramic after sintering reveals even better mechanical properties than that processed by a conventional pressing. This is attributed to the aligned alumina platelets, enhancing crack deflection and improving the fracture toughness from 6.8 ± 0.3MPa m0.5 (compacted) to 7.4 ± 0.3MPa m0.5 (DIW). The four-point bending strength of the DIW ATZ (1009 ± 93MPa) is also higher than that of the conventionally manufactured equivalent (861 ± 68MPa). Besides homogeneous ceramic, laminate structures are demonstrated. This work provides a valuable hybrid approach to additively manufacture tough and strong ceramic components.

Wrinkle Structure Regulating Electromagnetic Parameters in Constructed Core-shell ZnFe2O4@PPy Microspheres as Absorption Materials.

Structure engineering of magnetic-dielectric multi-components is emerging as an effective approach for presuming high-performance electromagnetic (EM) absorption, but still faces bottlenecks due to the ambiguous regulation mechanism of surface morphology. Here, a novel wrinkled surface structure is tailored on the ZnFe2O4 microsphere via a spray-pyrolysis induced Kirkendall diffusion effect, the conductivity of the sample is affected, and a better impedance matching is adjusted by modulating the concentration of metal nitrate precursors. Driven by a vapor phase polymerization, conductive polypyrrole (PPy) shell are in situ decorated on the ZnFe2O4 microsphere surfaces, ingeniously constructing a core-shell ZnFe2O4@PPy composites. Moreover, a systematic investigation reveals that this unique wrinkled surface structure is highly dependent on the metal salt concentration. Optimized wrinkle ZnFe2O4@PPy composite exhibits a minimum reflection loss (RLmin) reached -41.0dB and the effective absorption bandwidth (EAB) can cover as wide as 4.1GHz. The enhanced interfacial polarization originated from high-density ZnFe2O4-PPy heterostructure, and the conduction loss of PPy contributes to the boosted dielectric loss capability. This study gives a significant guidance for preparing high-performance EM composites by tailoring the surface wrinkle structure.

Development of high-performance composite via innovative route using water hyacinth extracted nanocellulose and analysis of its physical properties

This study focuses on the development of a high-performance composite using a novel technique incorporating nanocellulose extracted from water hyacinth. The extraction procedure of nanocellulose from water hyacinth stems involves acid hydrolysis and sonication, followed by its incorporation into jute, glass, and cotton fabric through the dip coating method. The crystallinity index of the nanocellulose was determined to be 40.72% using X-ray diffraction (XRD) analysis. Additionally, the functional groups of the extracted nanocellulose were identified through FT-IR analysis, while scanning electron microscopy (SEM) demonstrated morphological changes after nanocellulose coating. Our synthesized water hyacinth nanocellulose exhibited compliance with previously studied results in FT-IR analysis. Both tensile and flexural strength tests revealed that the nanocellulose coating significantly improved the strength of the jute, cotton, and glass fabric-reinforced composites compared to their raw counterparts. Specifically, the jute nanocomposite exhibited a 24.61% increase in strength, the cotton woven nanocomposite showed a 19.39% enhancement, and the glass nanocomposite displayed 8.47% increment in strength. Similarly, the flexural stress of jute and cotton fabric nanocomposites showed a notable 11% and 8.9% increase, surpassing the 3.59% rise observed in glass nanocomposites. Overall, this research successfully completed all tests and achieved superior findings compared to earlier studies.

Enhanced thermoelectric performance of Sr0.875La0.1TiO3-δ based composites through Bi-rich inclusions in internal and external reduction environments

The electrical transport performance of bulk SrTiO3 thermoelectric materials can be optimized by incorporating uniformly dispersed conductive inclusions. Herein, the impact of Bi2O3 addition on the thermoelectric properties of La-doped strontium titanate composite nano Ti powder (Sr0.875La0.1TiO3-δ/20 wt% Ti) has been examined. During the sintering process, Bi2O3 gradually transforms into a liquid phase to facilitate Redox reactions with nano Ti and mass transfer, followed by reduction and transformation into Bi–Bi2O3 particles that precipitate at grain boundaries. The presence of nanoscale Bi-rich phases reduces carrier transport barriers at grain boundaries and enhances phonon relaxation time associated with grain boundary scattering. Ultimately, the sample containing 10 wt% bismuth oxide exhibits the lowest lattice thermal conductivity and the highest weighted mobility. This led to a maximum power factor of 498 μW/mK2 at 873 K and a maximum ZT value of 0.188 at 1073 K. This study presents a novel approach to decouple electroacoustic transport through the utilization of Redox reactions between multiple phases, offering valuable insights for the development of high-performance thermoelectric oxide composites.

Static, dynamic and impact properties of a high-performance flax-fiber composite

As environmental issues become increasingly relevant nowadays, the need to develop new materials entirely or partially based on renewable resources is one fundamental step to reduce the consumption of fossil fuels and CO2 emissions. In that sense, natural fiber composites might represent an environmentally sustainable alternative to conventional solutions such as glass and carbon fiber composites, standard today for many lightweight structural applications; however, solutions are several and diverse in terms of technological process, base materials, mechanical properties, and analysis of their behaviour, necessary for safe industrial use, is still lacking for most resin-fiber combinations. Consequently, this work presents a comprehensive material characterization of a flax-fiber reinforced composite material, analyzing both the static and dynamic mechanical performances, targeting future crashworthiness applications. In particular static tensile, compressive, flexural and shear properties were investigated, while low-speed indentation, high strain-rate tensile and ballistic tests were carried out to probe the dynamic and impact features.

Experiment and finite element modelling on compressive and damage evolution of graphene nanoplatelet reinforced Porous cement composites

As reinforcing nano-fillers, graphene nanoplatelets (GNPs) have shown considerable promise for developing high-performance cement composites. However, the influence of GNP orientation and pores on the compressive and damage evolution of the GNP reinforced cement composites (GNPRCCs) remains unclear. This work employs three-dimensional finite element modeling along with experiments to provide fundamental insights into the property-microstructure relationships in the GNPRCCs. The model which incorporates GNP and pore as individual phases with cohesive interactions is developed and validated. The simulations reveal that the alignment of GNPs at 45° has the most significant effect on improving the load-bearing capacity and damage resistance of the GNPRCCs. A larger GNP diameter-to-thickness ratio is more beneficial for enhancing crack bridging and propagation control. The orientation and porosity of pores are evidenced to have significant effects on the damage behaviours of the GNPRCCs, where the pore shape shows negligible effects. These findings elucidate the underlying mechanisms that underpin the mechanical behavior of GNPRCCs, providing key guidelines to tailor and optimize the microstructural features for advanced construction materials with superior performance and durability.

Enhanced thermal conductivity of phase change composites with novel binary graphite networks

The thermal conductivity and porous structure of carbon-based networks significantly affect the heat exchange efficiency in phase change composites. However, simultaneously improving its thermal conductivity and controlling the formation of micrometer-scale open pores remains a significant challenge. In this study, a binary graphite network is constructed by both high-thermal-conductivity mesophase-pitch carbon fibers and high-textured pyrolysis carbon through chemical vapor deposition and ultra-high temperature graphitization, then embed paraffin to form high-performance phase change composites. The characteristic hierarchical pore structure in the binary graphite network facilitating the paraffin impregnation and its heat exchange efficiency is greatly improved by showing an optimum thermal conductivity of 144.78 W·m−1·K−1 and a phase change enthalpy of 87.4 J·g−1 at 0.6 g·cm−3 graphite skeleton and 51 wt% paraffin. The developed phase change composites hold great application potential in thermal control for space optical-mechanical systems and other critical aerospace components.

Tailored Out-of-Oven Energy Efficient Manufacturing of High-Performance Composites with Two-Stage Self-Regulating Heating via a Double Positive Temperature Coefficient Effect.

The needs for sustainable development and energy efficient manufacturing are crucial in the development of future composite materials. Out-of-oven (OoO) curing of fiber-reinforced composites based on smart conductive polymers reduces energy consumption and self-regulates the heating temperature with enhanced safety in manufacturing, presenting an excellent example of such energy efficient approaches. However, achieving the desired curing processes, especially for high-performance systems where two-stage curing is often required, remains a great challenge. In this study, a ternary system consisting of graphene nanoplatelets/HDPE/PVDF was developed, with a double positive temperature coefficient (PTC) effect achieved to fulfill stable self-regulating heating at two temperatures (120 and 150 °C). Systematic studies on both single and double PTC effects were performed, with morphological analysis to understand their pyroresistive behaviors. Compared to the oven curing process, up to 97% reduction in the energy consumption was achieved by the ternary system, while comparable thermal and mechanical properties were obtained in the carbon fiber/epoxy laminates. This work presents a new route to achieve OoO curing with two-stage self-regulating heating, which can be utilized in many high-performance composite applications.

An effective micro-arc oxidation (MAO) treatment on aluminum alloy for stronger bonding joint with carbon fiber composites

The micro-arc oxidation (MAO) treatment was used in this study to modify aluminum (Al) alloys to improve bond strength with carbon fiber reinforced polymer (CFRP). Various porous surfaces of Al alloy with better hardness, roughness and wetting were created. Void defects were reduced via using resin pre-coating (RPC) technique to guide high-viscosity epoxy into the holes, CNTs fiber bridging was constructed to improve bonding interface and epoxy adhesive layer. Combined treatments of “Na2SiO3 + KOH solution” MAO, RPC and introducing CNTs on Al alloy surface yielded 21.34 MPa, up to 156.1% increment over base strength. Original de-bonding failure on Al alloy surface was altered into dominant fiber tearing failure of CFRP composites, indicating the reinforced bond strength and stronger adhesive joint. MAO was the first try and proved as a feasible treatment for bond strength improvement, which could provide an alternative to manufacture high-performance Al-CFRP composites in industrial production.

Structural modeling and analysis of three-dimensional cross-linked braided preforms

Abstract Rotary braiding is widely used in the preparation of high-performance fiber composites. However, neither conventional rotary two-dimensional braiding nor rotary three-dimensional braiding can prepare three-dimensional preforms with low porosity and dense surface yarns. This article designs a three-dimensional cross-linked braiding equipment, describes the mechanism of carrier motion of three-dimensional cross-linked braiding, and obtains a numerical model of three-dimensional cross-linked braided preforms by establishing the spatial coordinate system of the braided chassis and using cubic B-spline curve fitting. The reasons for the large difference between the numerical model of preform and the real fabric are analyzed, and an optimization algorithm is proposed to make the fabric compact by gathering the yarn to the center of the fabric. The experimental samples are braided on a three-dimensional cross-linked braiding machine, and the reliability of the optimization algorithm is verified by comparing the yarn coordinates of the experimental samples with those of the optimized numerical model. The accurate establishment of the geometric model of the preform provides a solid foundation for carrying out the prediction of the mechanical properties of composite materials.

Resistance-welded thermoset composites: A Bayesian approach to process optimisation for improved fracture toughness

Joining thermoset composites via resistance welding offers a novel highly efficient assembly method for next-generation aerospace structures. Resistance-welded joints combine the benefits of bonding with the capacity for high-volume manufacturing rates and eliminate the need for complex surface preparation. The influence of key welding parameters on the joint performance is investigated by assessing the Mode I fracture toughness. Double Cantilever Beam specimens with different welding parameter combinations are manufactured, tested and compared with each other. Thermoset laminates are made weldable by co-curing a chemically compatible thermoplastic film with an uncured thermoset laminate. A Bayesian approach is used to study the correlation between processing parameters and to select parameters yielding high performance by training a Gaussian process emulator. Observed Mode I fracture toughness values are comparable to high-performance thermoplastic composites. This is equivalent to an improvement of approximately 290% in Mode I fracture toughness when compared to a co-cured thermoset joint.

Xylan cinnamoylation for reinforcing poly (butylene adipate-co-terephthalate): Molecule design and interaction optimization

PBAT composites with biomass fillers have gained considerable attention as alternatives to non-biodegradable plastics. This work employed xylan derivatives as fillers for PBAT composites. Xylan was modified by introducing cinnamoyl side groups which limit the hydrogen bonding and construct π-π stacking interactions with PBAT chains. The resultant xylan cinnamates (XCi) show degree of substitution (DS) of 0.55–1.89, glass-transition temperatures (Tg) of 146.5–175.0 °C and increased hydrophobicity, which can be simply controlled by varying the molar ratio of reactants. NMR results demonstrate that the C3-OH of xylopyranosyl unit is more accessible to cinnamoylation. XCi fillers (30–50 wt%) were incorporated into PBAT through melt compounding. The filler with a DS of 0.97 exhibited the optimal reinforcing effect, showing superior tensile strength (19.4 MPa) and elongation at break (330.9 %) at a high filling content (40 wt%), which is even beyond the neat PBAT. SEM and molecular dynamics simulation suggest improved compatibility and strengthened molecular interaction between XCi and PBAT, which explains the suppressed melting/crystallization behavior, the substantial increase in Tg (−34.5 → −1.8 °C) and the superior mechanical properties of the composites. This research provides valuable insights into the preparation of high-performance composites by designing the molecular architecture of xylan and optimizing the associated interactions.

Providing a strategy to restore damaged RC beam-column joints with the combination of CFRP and HPFRCC

This paper endeavors to assess the seismic performance of 3D reinforced concrete (RC) beam-column joints situated on the exterior of buildings, but lacking special ductility requirements. The joints have been rehabilitated by High-Performance Fiber-Reinforced Cement Composites (HPFRCC) and retrofitted using Carbon Fiber Reinforced Polymer (CFRP) wrap methodology. In this context, five beam-column joints located on the exterior of a structure have been subjected to cyclic lateral loading, while being scaled down to half their original size. The present study entailed an investigation into the cyclic behavior of three control specimens in its initial stage. Following the initial examination, it was observed that the control specimens, lacking any designated ductility standards, experienced significant core damage. During the subsequent phase of experimentation, the impaired concrete sections of the control samples were remediated through substitution with HPFRCC matter. Additionally, CFRP sheets were implemented for retrofit purposes. The modified specimens were then exposed to comparable cycles of loading. An analysis is conducted on the empirical findings of the specimens under investigation. The findings of this study indicate that the utilization of HPFRCC materials and CFRP sheets in the restoration and enhancement of deteriorated joints has led to a notable enhancement of their strength and displacement capacity. Specifically, this approach has facilitated the creation of a flexural plastic hinge and impeded the occurrence of shear failure within the core, leading to an improved overall behavior of the repaired damaged joint, which is comparable to that of undamaged seismic joints. The application of this technique demonstrates a high degree of efficacy in the rehabilitation and enhancement of edifices with deficient seismic details that have sustained damage subsequent to an earthquake event.

Facile, catalyst-free, and high enthalpy PEG-based phase change composite for use in photothermal conversion and waste heat recovery

The poor shape stability, low thermal storage density, and complex process confronted in fabricating high-performance phase change composites (PCCs) via the chemical cross-linking technology. Herein, PEG-based shape stability PCC (SSPCC) with high enthalpy and good shape stability was obtained using a facile one-pot method without additional catalysts. The reliable three-dimensional cross-linked structure formed by the interaction of epoxy resin and curing agent binds the movement of PEG molecular chains, which simultaneously in coupled with the stronger hydrogen bonding between PEG and cross-linked products to endow the as-prepared SSPCC with excellent shape stability, thermal stability, durability, and high thermal storage density (160.8 J/g). Moreover, the Raman spectra clearly presented the interaction force and phase morphology distribution between PEG and the skeleton structure. SSPCC with the high relative enthalpy efficiency and melt enthalpy can play an essential role in photothermal applications, while the facile manufacturing process free from additional organic solvents or high temperature, highlighting its green and sustainable features. Additionally, the photothermal transport and thermostatic effects of the SSPCCs show great potential for application in waste heat recovery, which can maintain higher temperatures for a long time. Totally, such SSPCC with reliable and distinguished phase change properties ensure a wide range of potential applications, while the easy-to-prepare and low-cost fabrication method provides an inspiring strategy for alternative SSPCC development.

All-in-one integrated flexible PE@PET/MXene films for high-performance electromagnetic shields with self-reinforced conductivity and mechanical properties

MXene-based composites are deemed as promising electromagnetic interference (EMI) shielding candidates to address the rapidly increasing electromagnetic interference and radiation concerns. However, developing high-performance flexible polymer-MXene composites with excellent EMI shielding efficiency (EMI SE), good mechanical properties and superior serving stability is a significant challenge. Herein, a type of all-in-one designed lightweight, thin, ultra-flexible PE@PET/MXene films are developed using a novel PE@PET nonwoven fabric (NWF) as the supporter. A mussel-inspired polydopamine modification facilitates the uniform loading of MXene, achieving high electrical conductivity of the resultant PE@PET/MXene films. A simple hot-pressing process is then employed to melt the sheath PE component of PE@PET to serve as a “self-glue” in adhering and wrapping the loaded MXene nanosheets, while maintaining the core PET fibers as the internal “steel” skeleton. As such, the resultant PE@PET/MXene films exhibit multiple self-enhancement metrics involving high mechanical strength, good electrical conductivity, robust serving stability, and superior EMI shielding performance. An optimized PE@PET/MXene film can preserve an excellent EMI SE of 50.44 dB and an ultra-high absolute shielding effectiveness (SSE/t) of 10606 dB cm2 g−1. The versatility of PE@PET/MXene EMI shielding films is further indicated by integrating the flame-retardant additives to endow its flame-retardant function, demonstrating excellent versability and expandability.

Multiscale Process Modeling of Semicrystalline PEEK for Tailored Thermomechanical Properties.

Polyether ether ketone (PEEK) is a semicrystalline thermoplastic that is used in high-performance composites for a wide range of applications. Because the crystalline phase has a higher mass density than that of the amorphous phase, the evolution of the crystalline phase during high-temperature annealing processing steps results in the formation of residual stresses and laminate deformations, which can adversely affect the composite laminate performance. Multiscale process modeling, utilizing molecular dynamics, micromechanics, and phenomenological PEEK crystal kinetic laws, is used to predict the evolution of volumetric shrinkage, elastic properties, and thermal properties, as a function of crystalline phase evolution, and thus annealing time, in the 306-328 °C temperature range. The results indicate that lower annealing temperatures in this range result in a faster evolution of thermomechanical properties and shrinkage toward the pure crystalline values. Therefore, from the perspective of composite processing, it may be more advantageous to choose the higher annealing rates in this range to slow the volumetric shrinkage and allow PEEK stress relaxation mechanisms more time to relax internal residual stresses in PEEK composite laminates and structures.

High-performance Fe–Si soft magnetic composites with controllable silicate/nano-Fe composite coating

The design of magnetic insulation coating structure has always been a challenge for high-performance soft magnetic composites (SMCs). In this work, we prepared Fe–Si SMCs with silicate/nano-Fe composite coating successfully by in-situ oxidation method combined with spark plasma sintering (SPS). The formation mechanism of the composite coating and its effect on the electro-magnetic properties of Fe–Si SMCs were investigated. The results showed that a uniform Fe2O3 coating can be obtained by reactions between Fe and H2O/O2 during in-situ oxidation process, and became thicker with the increased oxidation time. After sintering, the oxide coating was transformed into a composite coating composed of Fe2SiO4 with excellent insulation and nano-Fe with high ferromagnetism, which resulted from the interfacial reaction between Fe2O3 coating and Fe–Si core. The increased oxidation time led to the gradually thicker composite coating, and resulted in a linear decrease in saturation magnetization, indicating good controllability of the coating. However, excessive oxidation time led to the increased eddy current loss as well as the core loss due to the weakened resistivity. Thus, the Fe–Si SMCs exhibited high saturation magnetic induction (1.66T) and very low core loss (643.9 kW/m3 at 0.1 T/50 kHz) especially when the oxidation time was 1 h.

Enhancement of in-plane shear performance in masonry walls strengthened with high-performance fiber-reinforced cementitious composites

This study aims to design a high-performance fiber-reinforced cementitious composite (HPFRCC) material for reinforcing masonry walls and assess its impact on in-plane shear performance. Different specimens were compared, including an unreinforced one, a conventional mortar-reinforced one, and HPFRCC-reinforced specimens of varying thicknesses ranging from 10 mm to 20 mm. Aspects such as failure modes, shear stress–strain curves, pseudo-ductility, and energy dissipation were evaluated. Test results indicated that the unreinforced and mortar-reinforced masonry walls demonstrated brittle failure with wide cracks on both sides, whereas HPFRCC-reinforced walls exhibited ductile failure with controlled crack propagation owing to the excellent mechanical properties of HPFRCC, such as an average tensile strength of 7.32 MPa and a tensile strain capacity of 4.60 %. The HPFRCC significantly enhanced the shear strength and modulus of the masonry walls. The wall reinforced with 20 mm-thick HPFRCC showed a remarkable 26-fold increase in the energy dissipation capacity compared to the unreinforced one, and the 10-mm-thick and 15 mm-thick strengthening demonstrated 4.0- and 5.7-times improvement, respectively. The ideal HPFRCC overlay thickness was found to be between 15 mm and 20 mm. Beyond this thickness, gravitational flow and stiffness asymmetry negatively impacted shear performance.