Structural and Electrical Properties of the YSZ/STO/YSZ Heterostructure

The heterostructure thin films of yttria-stabilized zirconia (YSZ)/strontium titanate (STO)/YSZ with various thicknesses were deposited on MgO single crystal substrate by pulsed laser deposition (PLD) method. The structural and electrical properties of the YSZ/STO/YSZ heterostructure were studied through X-ray diffraction (XRD) and electrical conductivity measurements. The in-plane conductivities of the thin films were measured and compared with that of the bulk sample. The highest conductivities were reported for those samples with the thinnest YSZ (220) layers. The observed enhancement in the lateral ionic conductivity was probably caused by the combination of the misfit dislocation density and elastic strain in the interfaces. The enhanced ionic mobility was discussed in terms of the disorder introduced in the oxygen sublattice through the epitaxial strain at the interfaces

A Beam Test Study on the Bond Performance between Epoxy-Coated Reinforcement and Geopolymer Concrete

An epoxy-coated reinforcement geopolymer concrete structure with good durability and energy-saving properties can be formed by combining epoxy-coated reinforcement and geopolymer concrete. The bond strength is the precondition for the two to work together. In this paper, 13 beam specimens (11 epoxy-coated reinforcements and 2 ordinary deformed reinforcements) were designed to investigate the influence of the strength of geopolymer concrete, diameter of the reinforcement, bonding length and type of reinforcement on the bond performance between reinforcement and geopolymer concrete. The test results show that the ultimate bond strength of the epoxy-coated reinforcement (ECR) and geopolymer concrete decreased by 7.32% and 14.76%, respectively, when the rebar diameter increased from 14 mm to 16 mm and then to 20 mm. The ultimate bond strength between ordinary threaded reinforcement and geopolymer concrete was slightly higher than that between ECR and geopolymer concrete. When the length of the bond section is small or the concrete strength is low, the beam specimen is prone to the failure of the reinforcement pullout. The specimen with the larger reinforcement diameter is prone to concrete splitting failure. However, the specimens with medium bond length and small reinforcement diameter suffered from pull-out failure after concrete splitting. In this paper, based on the test data, the bond-slip constitutive model of ECR and geopolymer concrete was established, and the bond-slip curve obtained by this model was in good agreement with the measured curve. In addition, the calculation formula of the ultimate bond strength between ECR and geopolymer concrete was also proposed in this paper, which can provide theoretical reference for the engineering application of geopolymer concrete

Hydrothermal durability of unidirectional flax/carbon fiber hybrid composite plates

Hybrid carbon fiber/flax reinforced polymer composites (HFRPs) meet the requirements of high property to cost ratio for many structural applications. In the present study, HFRP plates produced with filament winding were studied on the property evolution subjected to 40 and 70 °C water immersion for eight-week. Water uptake and flexural properties of the HFRP samples were tested and analyzed in terms of the hybrid modes and fiber contents. The diffusion coefficient and equilibrium water absorption of fiber reinforced polymer composites increase and the performance deterioration intensifies with the increase in temperature. The equilibrium water absorption and the diffusion coefficient of the FFRPs are 7.6 and 3.8 times higher than those of the carbon fiber reinforced polymer composites (CFRPs), respectively. With the increase in the carbon fiber content, the hybrid samples showed a decrease in the water uptake and diffusion coefficient. HFRP with carbon fiber on the surface shows better hydrothermal resistance than other hybrid modes due to the barrier behavior of carbon fibers for water molecules. Fiber contents and hybrid modes also play a crucial role in the degradation of flexural properties. The flexural strength and modulus of HFRPs increase with increasing carbon fiber content but the nonlinear behavior becomes less obvious. The flexural strength and modulus of HFRPs with carbon fibers on the surfaces (CFC) are 3.59 and 7.96 times higher than those of the HFRP plates with flax on the surfaces (FCF) respectively. However, the significant water absorption in the flax layers deteriorates the stress transferring ability of the core flax layer, which causes the aging of CFC seriously

Tensile properties hybrid effect of unidirectional flax/carbon fiber hybrid reinforced polymer composites

To improve the mechanical properties of flax fiber reinforced polymer composites, flax/carbon fiber hybrid reinforced polymer composites were prepared by wet winding. The effects of carbon fiber volume fraction, carbon fiber monolayer thickness, and hybrid mode (carbon fiber dispersion) on the properties of hybrid composites were studied by tensile tests considering existing theoretical models. The results showed that the minimum repeating unit of flax fiber as skin and carbon fiber as core can yield a positive hybrid effect. In addition, a lower carbon fiber volume fraction reduced the carbon fiber monolayer thickness, and a higher degree of dispersion emphasized the positive hybrid effect of the hybrid composite. The stress–strain curves of the composite did not exhibit pseudo-ductility given the negligible difference in failure strain and large difference in modulus, such that the carbon fiber layer could not fracture multiple times. In an optimized hybrid composite, introducing 26.4% carbon fiber increased the composite strength by 129.3% compared with the flax fiber reinforced polymer and the composite toughness by 32% compared with the carbon fiber reinforced polymer

A Novel Wedge Anchor System for Double-Layer CFRP Plate Cables: Concept, Theoretical Analysis and FEA

This study introduces an innovative wedge anchor for double-layer carbon fiber reinforced polymer (CFRP) plate cable to address the current limitation of traditional wedge anchors. By employing the design concept of “secondary force transmission path”, the friction force for anchoring the CFRP plate is effectively transferred into the barrel through its contracting wedge, thus reducing the clamping pressure requirement of traditional wedge anchorage for anchoring thick or double-layer CFRP plates. Based on this conception, this study presents a theoretical analysis model for predicting the influence of parameter variations on the compressive stress of the CFRP plate, which can serve as a tool for rapid configuration preliminary design. Through finite element analysis, the internal stress distribution of the anchor is thoroughly investigated, and the theoretical analysis model for fast predicting compressive stress of CFRP plate is also validated. The results also indicate that the anchorage conception is valid and effective, providing sufficient anchorage of CFPR plates with an anchorage length of 100 mm

High-Temperature Resistance of Anchorage System for Carbon Fiber-Reinforced Polymer Composite Cable—A Review

Unidirectional carbon fiber-reinforced polymer (CFRP) may exhibit significant mechanical softening in the transverse direction at an elevated temperature. While significant transverse compressive stress exists on CFRP due to the clamping force from anchorage, a CFRP cable may exhibit anchorage failure when suffering an accidental fire disaster. The high-temperature resistance of a CFRP cable anchorage is critical, and clarifying the performance deterioration and failure mechanism of a CFRP cable anchorage system at elevated temperature is fundamental for clarifying its fire resistance. This paper reviews the current research status of the high-temperature resistance of CFRP cable anchorage systems from two aspects, including the high-temperature resistance of the comprising materials and the anchorage system. The reviews on the high-temperature properties of the comprising materials are summarized from two aspects. Firstly, the mechanical performance degradation of bonding epoxy resin at elevated temperatures and the effect of a filler on its mechanical–thermal properties are analyzed. Secondly, the mechanical performances of CFRP composites at elevated temperatures are summarized, with consideration of the stress state of the CFRP cable under the constraint of an anchorage device. The reviews on the high-temperature resistance of the anchorage system also include two aspects. Firstly, the temperature field solution method for the anchorage system is summarized and discussed. Secondly, the current research status of the anchorage performance at elevated temperatures is also summarized and discussed. Based on these reviews, the research shortage of the high-temperature resistance of CFRP cable anchorage systems is summarized, and further research is recommended

Fatigue Strength of End-Coped Crane Runway Girders

Fatigue cracks were found on a series of end-coped crane runway girders after 14 years of service in a steel mill building in China. Two typical crane runway girders with different spans were studied in this paper. Finite element analyses were conducted to investigate the stress concentration at the coped ends. Analytical results showed the stress concentration effect was highly localized and the stress concentration factor decreased with increasing cope radius and decreasing total depth. The analytical results agreed well with the field measured data. Fatigue tests were conducted to determine the fatigue strength using eight 1/5-scaled end-coped girder specimens. Based on the analytical results and limited test data, the fatigue strength for a maximum principal stress range of 103 MPa at 2 million cycles may serve as a possible design guideline for end-coped crane runway girders using the conventional S-N curves. Procedures for design and evaluation of the fatigue life of end-coped crane runway girders are suggested

Techno-economic-environmental assessment and performance comparison of a building distributed multi-energy system under various operation strategies

The distributed energy system (DES) is a promising technology that could enable decarbonization in the building sector. Comprehensive DES system assessment from a holistic perspective is crucial for system design, operation strategy selection, and performance optimization. This paper proposes a techno-economic-environmental integrated assessment model for comprehensive system evaluation. The DES configuration mainly includes a photovoltaic panel, ground source heat pump, gas turbine, absorption heat pump, and thermal storage tank. The system is simulated under three operation strategies with MATLAB/Simulink, which are following thermal load (FTL), following electric load (FEL), and following electric load with thermal storage (FELTS). Entropy-TOPSIS method is used to evaluate the DES's techno-economic-environmental performance under various operation strategies. The results indicate that the DES' primary energy efficiency ratio under the three operation strategies of FTL, FEL and FELTS are 51.49%, 86.78%, and 125.69%, respectively. The dynamic annual values are 1.05 × 10 6 CNY, 7.23 × 10 5 CNY, and 5.94 × 10 5 CNY, respectively. The total greenhouse gas emissions are 36.2 kgCO2eq/( m 2 ∙ a ) , 22.8 kgCO2eq/( m 2 ∙ a ) , and 16.4 kgCO2eq/( m 2 ∙ a ) , respectively. The entropy-TOPSIS analysis results showed that under FELTS operation strategy, DES performs the best; it has the best indicators for technical and environmental evaluation

Water absorption and property evolution of epoxy resin under hygrothermal environment

Changes in structure and properties of resin matrix caused by water absorption is one of the key factors affecting the long-term durability of fiber reinforced polymer composites used in civil engineering. In the present study, the water diffusion and structural change in an epoxy resin were investigated experimentally through immersion in deionized water at 40, 60 and 80 °C for 135 days. Water absorption, thermal, mechanical and microstructure analysis tests were conducted to evaluate the long-term property evolution. It was found that the water absorption of epoxy resin followed a two-stage model, including an initial Fick's diffusion response and a subsequent relaxation response. Long-term hygrothermal exposure brought about the structural change of epoxy resin, which led to the significant degradation up to 8%–30% in the mechanical properties and 21% in glass transition temperature, respectively. The resin plasticization and hydrolysis was the key factors for the degradation of thermal and mechanical properties. It was proved that the plasticization effect was reversible with the remove of bonding water after the drying. Based on the Arrhenius equation, the long-term life of flexural strength in two service environments were predicted to provide the application guideline. The significant degradation of flexural strength was occurred at the initial exposure of 2000 days and then reached to the stable strength retention of 69.6%

Mpox multi-antigen mRNA vaccine candidates by a simplified manufacturing strategy afford efficient protection against lethal orthopoxvirus challenge

Current unprecedented mpox outbreaks in non-endemic regions represent a global public health concern. Although two live-attenuated vaccinia virus (VACV)-based vaccines have been urgently approved for people at high risk for mpox, a safer and effective vaccine that can be available for the general public is desperately needed. By utilizing a simplified manufacturing strategy of mixing DNA plasmids before transcription, we developed two multi-antigen mRNA vaccine candidates, which encode four (M1, A29, B6, A35, termed as Rmix4) or six (M1, H3, A29, E8, B6, A35, termed as Rmix6) mpox virus antigens. We demonstrated that those mpox multi-antigen mRNA vaccine candidates elicited similar potent cross-neutralizing immune responses against VACV, and compared to Rmix4, Rmix6 elicited significantly stronger cellular immune responses. Moreover, immunization with both vaccine candidates protected mice from the lethal VACV challenge. Investigation of B-cell receptor (BCR) repertoire elicited by mpox individual antigen demonstrated that the M1 antigen efficiently induced neutralizing antibody responses, and all neutralizing antibodies among the top 20 frequent antibodies appeared to target the same conformational epitope as 7D11, revealing potential vulnerability to viral immune evasion. Our findings suggest that Rmix4 and Rmix6 from a simplified manufacturing process are promising candidates to combat mpox