Composite Strengthening Research Articles

Characterizations Strengthening and Wear Performance of the TIG Clad Ceramics Reinforced Hard Composites on TA18

Characterizations Strengthening and Wear Performance of the TIG Clad Ceramics Reinforced Hard Composites on TA18

The synergistic effect of nano-Al2O3 size and concentration on the interfacial adhesion properties of SMA/PDMS composites and their enhancement mechanism

Soft actuators composed of shape memory alloy (SMA) wires embedded in polydimethylsiloxane (PDMS) matrix hold potential for shape-morphing structures and soft robots. However, SMA exhibits poor bonding with PDMS due to its smooth and nonpolar surfaces. Nanoparticles show promise in interfacial strengthening of polymer composites. In this work, KH590 was used to modify nano-Al2O3 particles and deposited on the SMA surface, creating a three-dimensional nanostructure bridging SMA and PDMS to enhance interface strength. The synergistic effects of particle size and content of nano-Al2O3 particles on the interface strength were investigated in detail. It founds that interfacial strength decreased exponentially with particle size at content of 1 wt%, while when the content exceeds 1 wt%, the interface strength firstly increases with the particle size and then decreases in a logarithmic trend. Specifically, the interface strength is enhanced by 110 % with 3 wt% 50 nm particles. The interface enhancement mechanism was also discussed. The proposed nanoparticle modification approach was to strengthen SMA/PDMS interphase by increasing and extending fracture path, consuming more fracture energy. Chemical cross-linking also contributed to interface enhancement. This work enhances understanding of interfacial bonding mechanisms and provides valuable guide for interfacial strengthening of SMA/PDMS.

Highly protective and functional strengthening strategies for 3D printed continuous carbon fiber reinforced polymer composites: manufacturing and properties

Carbon fiber-reinforced polymer (CFRP) composites have gradually emerged as a crucial material in the aerospace industry. However, inadequate impact resistance and thermal stability limit survival in extreme environments. Inspired by the specific functions of multiple layers of tissue, from bird feathers to the musculoskeletal system. We propose low-cost composite strengthening strategies and efficient novel three-dimensional graphene aerogel manufacturing methods. A novel graphene aerogel/carbon fiber reinforced polymer (GAC) composite prepared by in-situ laser-induced graphene (LIG) layers on the surface of 3D-printed CFRP. GAC composites enhance CFRP's impact protection, thermal insulation, and electromagnetic shielding capabilities. For protection, GAC composites reduce low-velocity impact damage by 26.2%. The graphene layer can increase the thermal buffering capacity of the material four times, and the long-term service temperature can be increased by 40% compared to traditional CFRP. For functionality, the composites enable electromagnetic interference (EMI) shielding effectiveness of up to 50.2 dB. Furthermore, it can achieve surface heating above 400 °C and rapid de-icing through electrothermal effects. The simple and efficient processing method of GAC composites and tunable functionalities holds promise for the development of highly protective and intelligent aircraft skins.

Low-cost flash graphene from carbon black to reinforce cementitious composites for carbon footprint reduction

With the merits of high quality, cost-effectiveness, and high yield efficiency, flash Joule heating (FJH) emerges as an efficient means for mass production of flash graphene (FG). It creates prerequisites for the large-scale application of graphene in reinforcing cementitious composites, thus opening innovative possibilities for curbing carbon emissions and fostering the sustainable evolution of cementitious composites. In this study, two types of FGs, including high-purity FG (FG-G) and conductive FG (FG-D), are successfully synthesized via FJH process using carbon black as the carbon source. FG-G features a low ID/IG of 0.52, and exhibits higher graphitization and structural orderliness with fewer defects compared to the FG-D. The addition of 0.25 wt% FG-D increases the compressive strength, flexural strength, and flexural ultimate strain of cementitious composites by 16.48 MPa/16.8%, 1.43 MPa/37.2%, and nearly 2600 με/550%, respectively. The microstructure characterization results reveal that FG reduces the matrix defects, enhances both the matrix microstructure and calcium silicate hydrate gel nanostructure, which is advantageous for matrix refinement, inhibition of microcrack aggregation and propagation, and load transfer efficiency. Its disorderly stacked turbine structure also contributes to robust interface bonding and friction with cement matrix, thus facilitating the strengthening and toughening of cementitious composites. This study introduces a potential avenue to develop widely applicable and versatile silicon-based cementitious composites with high performance and low CO2 emission by using small carbon-based graphene as reinforcement.

Experimental study on seismic performance of seismic-damaged precast steel reinforced (recycled) concrete frame structure after strengthened and repaired

In order to understand the seismic performance and failure mechanism of the seismic-damaged prefabricated steel (recycled) concrete frame after strengthening and repairing, this paper uses four different strengthened methods, including carbon fiber reinforced polymer (CFRP), high-strength steel wire cloth (HSSWC), oblique support and enveloped steel jacket. Four seismic-damaged prefabricated steel (recycled) concrete frames were strengthened by single or composite strengthening, and low-cycle reciprocating failure tests were carried out on all frame specimens. The final failure mode of the reinforced specimens under simulated seismic load was observed. The seismic performance indexes such as load-displacement (P-Δ) hysteresis curve, skeleton curve, and stiffness degradation of each specimen before and after strengthening were compared and analyzed. The test results show that the strengthening methods used in this test can effectively restore the seismic performance of the seismic-damaged prefabricated steel (recycled) concrete frame. The specimens show a typical ductile failure mode, and the P-Δ hysteresis curve of the specimens is relatively full. For a single strengthened form, CFRP strengthened can more significantly restore and improve the ductility of the specimen than HSSWC strengthened, but the cumulative energy dissipation capacity of the specimen after HSSWC strengthened is stronger. The bearing capacity of the specimens after composite-strengthened is significantly improved, and the damage degree of the structure is reduced. The addition of oblique support and an enveloped steel jacket can provide greater lateral stiffness for the specimens and improve the failure mode of the specimens. The results of this paper can provide a scientific basis for the selection and design of strengthened methods for prefabricated steel-reinforced concrete structures after earthquake damage.

Enhanced mechanical properties of molybdenum alloy originating from composite strengthening of Re and CeO2

To enhance the mechanical properties of molybdenum alloys at both room and high temperatures, Mo−14Re−1CeO2 alloy was synthesized using the powder metallurgy method, and the corresponding microstructure and mechanical properties were characterized. The results indicate that the ultimate tensile strength of Mo−14Re−1CeO2 reaches 657 MPa, with a total elongation of 35.2%, significantly higher than those of pure molybdenum (453 MPa, and 7.01%). Furthermore, the compression strength of Mo−14Re−1CeO2 at high temperature (1200 °C) achieves 355 MPa, which is still larger than that of pure molybdenum (221 MPa). It is revealed that there is a coherent interface between CeO2 and the Mo−14Re matrix with CeO2 particles uniformly distributed in both intergranular and intragranular regions. The improvements in mechanical properties are primarily attributed to the formation of Mo−Re solid solution, grain refinement, and dispersion strengthening effect of CeO2.

The Effects of Different Ultrasonic Composite Surface Modifications on the Properties of H13 Steel for Shield Tunnel Machine Cutter Ring

Tunnel boring machines (TBMs) are exposed to the impact of the ground shattering force and the friction of sandstone during excavation work, and are prone to wear and breakage, and other failures. Traditional heat treatment processes cannot simultaneously achieve the required high-energy composite structure of hard external and tough internal properties for cutter rings, leading to inadequate wear resistance and impact toughness under working conditions. This study utilizes H13 steel as the base material, and based on a study of carburizing, nitriding, and ultrasonic impact processes for H13 steel analyzing the effects of different high-energy composite modification processes on the hardness distribution, microstructure, and residual stress of H13 steel, the mechanisms by which high-energy composite modification processes affect the wear resistance and impact resistance of H13 steel are revealed. The results indicate that the wear amount and impact toughness of the sample subjected to carburizing and ultrasonic surface rolling composite strengthening were 1.9 mg and 27.34 J/cm2, demonstrating the best wear and impact resistance. This combination of properties allows the H13 steel cutter ring to achieve the optimal overall performance in terms of wear resistance and impact resistance.

Flexural behavior of reinforced concrete beams externally strengthened with ECC and FRP grid reinforcement

To prevent premature delamination of FRP sheets in strengthened concrete structures, this study explores a novel method of laying a composite layer of fiber reinforced polymer (FRP) grid reinforced with engineering cementitious composite (ECC), designated as FGRE, and applied at the soffit of reinforced concrete (RC) beams to improve its flexural performance. Experimental studies were conducted on RC beams with different strengthening configurations to validate the effectiveness of the proposed strengthening method. In addition, analysis on the working mechanism and a parametric analysis were performed for the composite strengthened beam using nonlinear finite element modeling. The experimental results showed that FGRE composite layers can significantly improve the bearing capacity of RC beams. Compared with the control RC beam, the FGRE composite strengthening technique significantly increased the cracking load, yield load, and ultimate load of the beam specimens up to 28, 11, and 12 %, respectively. The ECC grout layer maintained a good bonding performance with the concrete substrate until beam failure. The flexural capacity of RC beams with the proposed FGRE strengthening systems is determined by the thickness of the ECC layer. In addition, the effect of strengthening on the flexural capacity was more significant when the yield and tensile strength of the steel reinforcement were lower. Moreover, the prediction deviation from the experimental data of the FE models and analytical models for the ultimate load-bearing capacity were less than 2 and 7 %, respectively. It can be concluded that the proposed FGRE system is a viable solution to enhance the flexural capacity of RC beams.

Axial compressive performance of RC columns strengthened with prestressed CFRP fabric and UHPC jacket with spiral stirrups

AbstractTo address the issue of easy shearing damage of Carbon Fiber Reinforced Polymer (CFRP) in enhancing the axial compressive performance of CFRP and Ultra‐High‐Performance Concrete (UHPC) strengthened concrete columns, two methods, prestressed CFRP and UHPC with spiral stirrups, were employed for composite strengthening of reinforced concrete (RC) columns. A total of one unstrengthened column and eight strengthened columns were designed and fabricated to validate the effectiveness of the proposed methods. The axial compressive performance and bearing capacity of each specimen were analyzed by considering parameters such as single or composite strengthening method, presence of spiral stirrups in UHPC, and application of pre‐stressed CFRP. The results show that, compared with any single strengthened specimen, the ultimate bearing capacity of the composite strengthened specimen is greater than the sum of the corresponding single strengthened specimens, and the bearing capacity of the prestressed CFRP with spiral stirrup UHPC composite strengthened specimen is the most significant, reaching 235.63%. By incorporating spiral stirrups in the UHPC jacket, the phenomenon of uneven fragmentation during the failure of the strengthened column is improved. This helps prevent premature shearing damage of CFRP and enhances the fracture strain and effective utilization of CFRP. Additionally, prestressed CFRP effectively restrains the lateral deformation and crack development of the core concrete in the UHPC jacket, fully utilizing the high compressive strength of UHPC. This further enhances the ultimate bearing capacity and ductility of the specimens. Based on the experimental phenomena and strain of each material, the failure mechanism of prestressed CFRP‐spiral reinforced UHPC composite‐strengthened columns is proposed. Finally, a unified bearing capacity calculation formula for single and composite strengthened columns is established, based on the theory of confined concrete strength and the assumption of strength increment superposition. The formula is validated with experimental results from relevant literature, showing small errors in the calculated results and indicating good applicability of the formula.

In situ experimental study on possible strengthening and toughening mechanism of interlaminar pores in carbon fiber orthotropic laminates

In order to study the regulation mechanism between the internal micro-pores and the mechanical properties of carbon fiber orthogonal laminated composites. In this paper, a kind of carbon fiber orthogonal laminated composite with different types of interlaminar micro-pores was carried out in-situ loading experiments by SR-CT, and the internal fibers, pore microstructure and damage of the sample in the process of progressive failure were tracked in the whole field and in real time. Through in-situ experiments, special phenomena such as three times reduction progressive failure of the material loading curve, secondary cracking of the fiber layer, and crack arrest by porosity was observed, Furthermore, through the analysis of the two special stages of strength improvement and toughness enhancement of the loading curve, it is found that the strengthening mechanism of the orthogonal laminated structure to realize the repeated strength improvement of the material by controlling the interlaminar alternating shear action, and the toughening mechanism of crack tip passivation induced by micro-pores. It provides a possible way to realize the strengthening and toughening of composites through the design of microporous structure.

Microstructure evolution and composite strengthening mechanism during solid solution and aging treatment for Cu-Ni-Co-Si sheet

A type of Cu-Ni-Co-Si alloy was designed and conducted by solid solution and aging treatments. Meanwhile its microstructure evolution and performance evolution were also studied. The characteristics of precipitated phases after aging treatment, and the strengthening mechanism of the process have been thoroughly studied. The results indicate that the optimal process for Cu-Ni-Co-Si alloy is solid solution at 900 °C for 120 min and aging at 500 °C for 240 min, respectively. At peak aging, the alloy reached tensile strength and conductivity of 631 MPa and 41.3 % IACS, respectively. The grain orientation of the aged alloy is complex; besides it is equiaxed; and there are a large number of twins and dislocation lines in the crystal. The matrix contains both Co2Si large-grained precipitated phases and orthorhombic, nanoscale precipitated phases of (Ni,Co)2Si; with sizes in the range of 5–8 nm. (Ni,Co)2Si is the main strengthening phase of the alloy after aging treatment due to its fineness and diffuseness. Solid solution and aging treatment improve microstructure and comprehensive properties of materials, and validated the theoretical guidance and feasibility in practical applications through high-precision quantitative calculations.

Influence of microstructure evolution and element segregation on high temperature tensile behaviors in GH4706 alloy

This work systematically investigated the influence of microstructure evolution and element segregation on tensile properties and fracture behaviors of GH4706 superalloy under different temperatures (25 °C, 400 °C, 500 °C, 600 °C and 650 °C). The advanced methods of TEM, AES and SIMS were conducted to characterize the variation of microstructure and element distribution. Experimental results showed that the yield and tensile strength of the test alloy decreased while the corresponding elongation increased as the increment of test temperature. The dominated fracture mode was intergranular brittle fracture at the temperature of 25 °C, gradually transforming to ductile dimple fracture as the temperature increased. This phenomenon was determined to be closely related to the increment of average grain size and size of γ'/γ″ coprecipitates as temperature rose. It was worth noticing that the elongation performed abnormally low (16.3%) at the temperature of 500 °C, exhibiting intermediate temperature brittleness (ITB) phenomenon. The SIMS analysis showed that the segregation of S towards grain boundary was the most obvious at the temperature of 500 °C, which was considered as the main factor leading to ITB. In addition, the coarsening of carbides at grain boundaries and local strain non-uniformity caused by dislocations could also resulted in ITB. The main reason for maintaining good strength and plasticity at the temperature of 650 °C was contributed to the softening of γ' phases by repeated cutting of dislocations and deformation twins, reducing the hindrance to the movement of dislocations. Moreover, composite strengthening effect of P and B could improve bonding strength, stabilize grain boundaries, and effectively suppress the initiation of intergranular cracks.

Enhanced strength–ductility synergy in Ti55531 titanium alloys through gradient microstructural design strategy

The strength-ductility trade-off dilemma still exists for titanium alloys, which is a challenging and pressing issue within the realm of microstructure design and property control. In the present work, a typical axial gradient microstructure was prepared in Ti55531 titanium alloy through a composite strengthening process involving rapid electropulsing treatment (EPT) combined with step-quench treatment (SQT). The results show that a significant improvement of 450 MPa (54 %) and 6.3 % (100 %) for the strength and ductility are obtained respectively for gradient microstructure by EPT + SQT (GMES) compared to that gradient microstructure prepared by EPT (GME) only. This indicates that the enhanced strength-ductility synergy observed in GMES is attributed to the characteristic Twinning induced Plasticity (TWIP) mechanism employed in this novel design of gradient microstructure. Furthermore, a detailed analysis and discussion are provided on the physical deformation mechanism and crack initiation behaviour of the gradient microstructure, providing valuable insights for the design of high-strength, high-ductility metals such as beta titanium alloys, advanced steels, and multi-phase alloys.

Corrosion studies of duplex surface-treated M420 stainless steel by plasma nitrocarburizing and WCrAlTiSiN multilayer coating

M420 stainless steel has good mechanical properties, but its corrosion resistance is poor, which limits its application in marine conditions. Single-technology processing has been unable to meet the development needs of modern industry. In this work, plasma nitrocarburizing (PNC) and CrN/CrTiAlSiN/WCrTiAlN multi-layer coating were carried out on M420 martensitic stainless steel by hollow cathode-assisted plasma treatment and multi-arc ion plating, respectively. The modified layers were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The results show that the nitrocarburized layer effectively improves the hardness gradient between the coating and the substrate. The presence of the composite strengthening layer enables the sample to obtain a thick and dense corrosion-resistant surface, effectively blocking the invasion of the corrosive medium. The corrosion rate of the PNC + C sample decreased by an order of magnitude. Combining hollow cathode-assisted rapid nitrocarburizing technology and multi-arc ion plating technology can significantly improve the mechanical properties and corrosion resistance of M420 stainless steel in a shorter time. The duplex surface-treated M420 stainless steel by plasma nitrocarburizing and WCrAlTiSiN multilayer coating exhibited excellent corrosion resistance compared to the nitrided and coated M420 stainless steel.

Composite strengthening via stress-concentration regions softening: The proof of concept with Schwarzites and Schwarzynes inspired multi-material additive manufacturing

Inspired by nature, porous graded topological structures based on carbon, like Schwarzites and Schwartzynes, exhibit a distinctive radial-gradient distribution of pores. The pores are strategically arranged in two patterns: small pores at the centre and larger pores in the outer region (ψ), and larger pores at the centre with smaller pores in the outer region (Ω). This type of topological engineering, with its unique deformation behaviour, makes these structures highly suitable for engineering applications requiring high energy absorption. However, the existence of stress-concentration regions within the porous graded structures leads to premature structural failure during uni-axial compression. To enhance the mechanical properties of such porous graded structures, this study proposes a strategy of tailoring their pores' deformation characteristics by replacing the stress concentration regions with soft/flexible materials. The selective reinforcing two (ψ2) and three layers (Ω3) soft material enhances the specific yield strength of the multi-material composite by 187.27 % and 230.22 %, respectively compared to the respective porous soft structures. Specific resilience is heightened by 289.93 % and 323.82 % for multi-material composite ψ2 and Ω3, w.r.t the respective porous hard structure(ψ0′ and Ω0,). Our results present a unique strategy for improving the structural performance of the porous graded structures by tailoring the deformation characteristics. Engineered multi-material-based advanced composites, resulting from this approach, exhibit significant potential for applications requiring energy absorption without failure.

Effect of titanium-based additives on the strengthening of tungsten composites

To meet the high demand of tungsten alloy matrix wires for photovoltaic slicing, new high performance tungsten composites are explored and the effect of various Ti-based additives on the mechanical properties of tungsten is systematically discussed as well as the corresponding strength improvement mechanism. It is found that the W-TiB2 exhibits the best mechanical properties with an ultimate tensile strength of 292.3 MPa and a compressive strength of 2370 MPa (a strain of 35%), approximately 96.1% and 28.5% higher than those of pure tungsten, respectively. Besides, the TiB2 additive also triggers a slight toughening with a transgranular fracture. The enhanced strength should be attributed to the reaction between TiB2 and adsorbed/dissolved oxygen, in which a new second phase of TiO2 is generated with a small amount of Ti elements solidly dissolved into the W matrix, resulting in enhanced binding ability among grain boundaries and distorted lattices.

Modulation of microstructure and improvement in the mechanical properties of TiBw/Ti65 composites by rolling at different temperatures

The effect of rolling temperature on microstructure evolution and mechanical properties of as-sintered TiBw/Ti65 composites was systematically investigated. The results showed that at 900 °C (in the low α + β phase region), the matrix microstructure primarily exhibited a deformation structure. At 1000 °C (in the high α + β phase region), a bimodal structure was observed, and at 1100 °C (in the β phase region), a basket-weave structure emerged. Additionally, silicides precipitated at 900 °C were fine but grew and coarsened at 1000 °C, eventually dissolving almost completely into the matrix at 1100 °C. This behavior is attributed to the varying solubility of silicides in the α and β phases. With increasing rolling temperature, the dynamic recrystallization (DRX) mechanism within the TiBw/Ti65 composites transitioned from continuous dynamic recrystallization (CDRX) to discontinuous dynamic recrystallization (DDRX). Rolling significantly enhanced the mechanical properties of the composites. The HR-900 composite exhibited the optimal strength-plasticity combination at room temperature, achieving an ultimate tensile strength (UTS) of 1415 ± 21 MPa and elongation (EL) of 6.2 ± 2.7%, mainly due to grain refinement and work hardening. Conversely, the HR-1100 composite demonstrated superior high-temperature mechanical performance, showing improvements of 37.18%, 27.05%, and 9.59% at 963 MPa (650 °C), 789 MPa (700 °C), and 560 MPa (750 °C), respectively, compared to those of the as-sintered materials. The strengthening mechanisms were fine-grain strengthening, dislocation strengthening, and load transfer strengthening of the as-rolled composites, and the primary strengthening mechanism shifts from dislocation to fine-grain strengthening as the rolling temperature increases.

Multifunctional 58S Bioactive Glass/Silver/Cerium Oxide-Based Biocomposites with Effective Antibacterial, Cytocompatibility, and Mechanical Properties.

58S bioactive glass (BG) has effective biocompatibility and bioresorbable properties for bone tissue engineering; however, it has limitations regarding antibacterial, antioxidant, and mechanical properties. Therefore, we have developed BGAC biocomposites by reinforcing 58S BG with silver and ceria nanoparticles, which showed effective bactericidal properties by forming inhibited zones of 2.13 mm (against Escherichia coli) and 1.96 mm (against Staphylococcus aureus; evidenced by disc diffusion assay) and an increment in the antioxidant properties by 39.9%. Moreover, the elastic modulus, hardness, and fracture toughness were observed to be increased by ∼84.7% (∼51.9 GPa), ∼54.5% (∼3.4 GPa), and ∼160% (∼1.3 MPam1/2), whereas the specific wear rate was decreased by ∼55.2% (∼1.9 × 10-11 m3/Nm). X-ray diffraction, high-resolution transmission electron microscopy, and field emission scanning electron microscopy confirmed the fabrication of biocomposites and the uniform distribution of the nanomaterials in the BG matrix. The addition of silver nanoparticles in the 58S BG matrix (in BGA) increased mechanical properties by composite strengthening and bactericidal properties by damaging the cytoplasmic membrane of bacterial cells. The addition of nanoceria in 58S BG (BGC) increased the antioxidant properties by 44.5% (as evidenced by the 2,2-diphenyl-1-picrylhydrazyl assay). The resazurin reduction assay and MTT assay confirmed the effective cytocompatibility for BGAC biocomposites against mouse embryonic fibroblast cells (NIH3T3) and mouse bone marrow stromal cells. Overall, BGAC resulted in mechanical properties comparable to those of cancellous bone, and its effective antibacterial and cytocompatibility properties make it a good candidate for bone healing.

Synergistic strengthening of Al matrix composites by in situ pyrolysis of C and precipitation of nanophases

Synergistic strengthening of Al matrix composites by in situ pyrolysis of C and precipitation of nanophases

Carbon Fiber Reinforced Polymer Adoption for Structural Rehabilitation

ABSTRACT Flexural strengthening is essential when structures face increased loads or usage changes, requiring localized reinforcement. Carbon Fiber Reinforced Polymers (CFRP) are widely used for repairing deteriorating concrete elements, notably boosting their flexural and shear strength and prolonging their lifespan. However, CFRP applications may encounter challenges like delamination. Therefore, it is important to select a good product and adhesive to enhance the performance of the fiber. The purpose of this study is to propose proper composite strengthening for a reinforced concrete structure to increase its flexural and shear capacity. A case study of a small office building in Italy is selected and one sectional frame consisting of six beams is studied. The first step in this process is to assess the moment and shear forces due to the initial loads based on the existing longitudinal and shear reinforcement. Then, the moment and shear forces due to the upgraded loads are calculated using SAP 2000 to determine if flexural strengthening is needed for any of the six beams being analyzed to avoid ductile failure of the steel rebars and brittle failure of the concrete. The use of CFRP showed positive results in terms of structural rehabilitation for the building, particularly when subjected to elevated loads. This not only contributes to the building’s overall safety but also extends its service life, making it a valuable and sustainable solution for structural enhancement in the face of varying load conditions.