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2.5D woven composite has great application prospect in high bypass ratio commercial turbofan engine fan blades due to its comprehensive advantages in mechanical properties and complex component forming. For the aero-engine fan blades, vibration fatigue is a working condition that can not be ignored. At present, the research on vibration fatigue behavior of 2.5D woven composite is limited, and there is a lack of numerical model for vibration fatigue behavior simulation. In this paper, a multi-scale model for the first-order flexural vibration fatigue behavior of a 2.5D woven composite cantilever beam simulating the root of engine blade was established. Adopting the fatigue loading simulation method which adopted the fixed cycle jumping strategy, and the damage initiation criterion and fatigue stiffness degradation model based on the leading fatigue failure mechanism, the vibration fatigue test processes of the wrap and weft specimens were simulated respectively. With the established multi-scale model, the stress field in the unit cell of the dangerous part of the specimen was analyzed, and the damage state of the specimen after the vibration fatigue test was predicted. The numerical simulation results are consistent with the observed fracture morphology after the test, which verifies the validity of the proposed multi-scale prediction model for vibration fatigue of 2.5D woven composite materials. In addition, based on the multi-scale prediction model of vibration fatigue proposed in this paper, the damage states in the unit cell at the working section of the wrap specimen with the accumulation of fatigue loading cycles simulated, which is helpful to understand the evolutionary mechanism of vibration fatigue damage of 2.5D woven composite materials.

The BN coating was deposited on the surface of typical domestic SiC fibers by chemical vapor permeation (CVI) process, and the fibers were oxidized at 800-1200 ℃ for 1 h. The morphology, structure and composition of BN coated SiC fibers after oxidation were characterized. The property changes of BN coated SiC fibers after oxidation were evaluated by tensile strength of monofilament. The results show that when the oxidation temperature is lower than 1000 ℃, the BN coating and its oxide can effectively prevent the erosion of the inner SiC fibers by O2, and when the temperature continues to rise, the SiC fibers are oxidized. With the increase of oxidation temperature, the surface oxide of BN coated SiC fibers goes through the process of α-B2O3→SiCxOy→amorphous SiO2. The tensile strength of BN coated SiC fibers decreases with the increase of oxidation temperature. Direct exposure of BN coating to oxidizing environments reduces the oxidation resistance of SiC fibers. The failure source of fiber fracture first transitions from BN coating defects to B2O3 oxide layer defects and finally evolves into SiO2 oxide layer porosity defects.

Short beam shear (SBS) test combined with digital image correlation (DIC) can quickly identify the multiple mechanical properties of unidirectional fiber reinforced resin matrix composites. In addition, the complete interlaminar shear stress-strain behavior and interlaminar shear strength of composite materials under uniaxial stress state can be obtained, which is very important to establish the strength criterion of three-dimensional stress state of composite materials with thick section. In order to study the influence of experimental design on the identification accuracy of interlaminar shear mechanical parameters of materials, two stereo digital image correlation systems composed of four CCD cameras were developed for the first time in this paper, and the strain distribution in the front and back surface gage regions of the sample during loading in SBS test was measured. The experimental results show that the shear strain distribution on the front and back surfaces of the sample is asymmetrical, and the relative deviation is up to 44%, because of the thread clearance of fixture and insufficient fixture stiffness. On the one hand, a new method is proposed to identify the shear mechanical properties of materials according to the asymmetrical distribution of shear strain on the front and back surfaces of the sample. By using DIC technology and finite element model updating (FEMU), the measured average shear strain in the distance region of the front and back surfaces of the specimen and the variance of the calculated strain data at the corresponding position of the finite element model are used as the objective function to identify the constitutive parameters and off-axis angles. The complete nonlinear shear constitutive parameters can be obtained, and the identification process is not sensitive to the initial parameters. On the other hand, by improving the test fixture to improve the tool stiffness, the phenomenon of asymmetric shear strain distribution is eliminated, and the complete interlaminar shear stress-strain constitutive relationship parameters of unidirectional laminates are accurately identified.

Buoyant materials, as an important counterweight material of the deep-sea devices, play an important role in providing the equipment with enough buoyance as much as possible. Solid buoyant materials (SBMs) have received extensively attention in deep-water surveying and development and petroleum exploration fields in recent years due to their low density, high strength and low water absorption characteristics.In this paper, the classification and the application of SBMs and their recent developments both at home and broad were firstly discussed. Typically, the SBMs can be mainly divided into the chemical and the composite syntactic foams according to their chemical composition and the composite syntactic foam was especially elaborated in this study. Secondly, four basic types of the composite syntactic foams, namely metal-, polymer-, and ceramic- matrix and other types of the syntactic foams, based on their chemical composition of the matrix and the reinforcement. The influence factors such as the essential composition, the surface microstructure, and the loading rate on the physical, mechanical, and the failure mode of the syntactic foams were summarized. The dynamical behavior and failure mechanism under different loading rates can be analyzed and revealed by the computed X-ray tomography technique combined with the finite element method. The prospects of improving overall mechanical performance and advanced experimental characterization methods of syntactic foams are summarized as follows: the overall mechanical performance can be improved by modifying functional groups of filler and resin matrix or adding a second reinforcement phase; the microstructure can be characterized and the failure mechanism revealed by means of μ-CT and scanning electron microscope.

The increasing prevalence of drug-resistant bacteria has prompted the search for alternative approaches to address bacterial infections. Lanthipeptides, which are small molecule peptides, are biosynthesized and post-translationally modified by ribosomes in gram-positive bacteria. These compounds possess distinctive target recognition properties, making them highly potential candidates for combating antimicrobial resistance. Consequently, they hold promising potential as innovative substitutes for traditional antibiotics. We conducted a comprehensive analysis of 65 publicly available Bacillus amyloliquefaciens genomes' data to explore the potential for lanthipeptide synthesis in this species. We annotated 21 putative precursor peptide genes for these novel lanthipeptides. Through heterologous expression experiments, we successfully obtained a novel lanthipeptide named amyA3. We accomplished a novel co-transformation strategy by introducing the synthetic enzyme obtained from B. amyloliquefaciens WS-8 into the E. coli BL21 (DE3) strain along with the heterologous precursor peptide amyA3. Through mass spectrometry analysis, we confirmed the successful modification of amyA3 by the synthetic enzyme derived from B. amyloliquefaciens WS-8, which represents a significant breakthrough in this research field. The identification and characterization of the lanthipeptide amyA3 along with the elucidation of its biosynthetic pathway provide novel perspectives into the discovery of naturally derived products and the intricate processes of translation and post-translational modifications. [ABSTRACT FROM AUTHOR]

Short beam shear tests conbined with digital image correlation were carried out for thick-section glass fiber reinforced resin matrix composites, and the variation of interlaminar shear behavior of unidirectional composites with different thicknesses with thickness was obtained. In order to explore the size effect mechanism of interlaminar shear mechanical behavior of materials, the microscopic characteristics of pores of samples with different thicknesses were observed through scanning electron microscope photos of sample slices. Image processing was used to obtain the contours of irregular pores, and parameters for quantitative characterization of microscopic characteristics were proposed. A three-dimensional representative volume element(RVE) model containing fibers, matrix, fiber/matrix interface and pores was randomly generated, and the effect of irregular pores of different sizes and distributions on the interlaminar shear strength of composites was studied by numerical analysis. The results of short beam shear tests showed that the interlaminar shear mechanical behavior of unidirectional composites was independent of the thickness of the specimens, but the shear strength decreased with the increase of the thickness of the specimens. The image analysis results showed that the distribution law, size, concentration and irregularity of the pores in samples of different thicknesses were significantly different. The numerical analysis results of RVE showed that the damage was caused by the destruction of the fiber-matrix interface close to the pores, and the interlaminar shear strength of thick-section composites decreased with the increase of the maximum pore size under the same porosity. At the same time, pore concentration and porosity also have a significant effect on the interlaminar shear strength of the material. The above experimental and analytical results show that the size effect of the interlaminar shear strength of thick-section composite materials is related to the microscopic characteristic parameters of the material pores. As the thickness of the composite material increases, the porosity, maximum pore size and concentration increase, and the shear strength decreases. Therefore, the difference in the microscopic characteristics of pores in materials of different thicknesses is one of the important mechanisms that lead to the decrease in the interlaminar shear strength of the material. [ABSTRACT FROM AUTHOR]

Based on the three-point bending test, the bending performances of S6C10-800/AC318 composite unidirectional plates with different span-thickness ratios (hereinafter referred to as unidirectional plates) were tested, and the effect of span-thickness ratio on the bending strength and bending modulus of unidirectional plate was studied. The influence and fracture mode of the specimens with different span-thickness ratios were analyzed to obtain the bending failure mechanism, and the critical span-thickness ratio of three-point bending test of unidirectional plate was determined. The results show that the bending strength of the unidirectional plate increases with the increase of the span-thickness ratio, and the bending modulus first increases and then decreases with the increase of the span-thickness ratio. The fracture mode of the unidirectional plate changes when the span-thickness ratio α＝20, and the degree of delamination damage of unidirectional plate gradually decreases with the increase of span-thickness ratio, but the degree of splitting increases. When α≤20, the stress-strain curve conforms to the linear relationship with the increase of the span-thickness ratio, but when α＞20, the stress-strain curve does not conform to the linear relationship. Therefore, the predicting formula of bending strength of unidirectional plate under arbitrary span-thickness ratio and a failure criterion for three-point bending test of unidirectional plate are obtained. It is recommended that the critical span-thickness ratio of the three-point bending performance test of unidirectional plate is 20. This is of great significance for optimizing the three-point bending test method of glass fiber composite materials to more accurately test the bending performance of composite materials.

Echinococcus granulosus causes echinococcosis, an important zoonotic disease worldwide and a major public health issue. Vaccination is an economical and practical approach for controlling E. granulosus. We have previously revealed that a recombinant protein P29 (rEg.P29) is a good vaccine candidate against E. granulosus. However, T cell immunogenic epitopes have not been identified. In the present study, we use rEg.P29-immunized mice as models to screen immunogenic epitopes for the construction of a novel multi-epitope vaccine. We search for immunodominant epitopes from an overlapping peptide library to screen the peptides of rEg.P29. Our results confirm that rEg.P29 immunization in mice elicits the activation of T cells and induces cellular immune responses. Further analyses show that a T cell epitope within amino acids 86–100 of rEg.P29 elicits significant antigen-specific IFN-γ production in CD4+ and CD8+ T cells and promotes specific T-cell activation and proliferation. Collectively, these results provide a reference for the construction of a novel vaccine against broad E. granulosus genotypes based on epitopes of rEg.P29.

Aims: Traumatic brain injury (TBI) stands as a significant concern in public health, frequently leading to enduring neurological deficits. Long non‐coding RNA H19 (lncRNA H19) exerts a potential regulator role in the pathology of brain injury. This study investigates the effects of lncRNA H19 knockdown (H19‐KD) on the pathophysiology of TBI and its potential neuroprotective mechanisms. Methods: Controlled cortical impact was employed to establish a stable TBI mouse model. The expression levels of various genes in perilesional cortex and striatum tissue after TBI was detected by RT‐qPCR. AAV9‐shRNA‐H19 was injected into the lateral ventricle of mice to knockdown the expression of lncRNA H19. Various behavioral tests were performed to evaluate sensorimotor and cognitive functions after TBI. Immunofluorescence and Nissl staining were performed to assess brain tissue damage and neuroinflammation. The Nrf2 and HO‐1 expression was performed by Western blot. Results: After TBI, the expression of lncRNA H19 was elevated in perilesional tissue and gradually reverted to baseline. Behavioral tests demonstrated that H19‐KD significantly promoted the recovery of sensorimotor and cognitive functions after TBI. Besides, H19‐KD reduced brain tissue loss, preserved neuronal integrity, and ameliorated white matter damage at the histological level. In addition, H19‐KD restrained the pro‐inflammatory and facilitated anti‐inflammatory phenotypes of microglia/macrophages, attenuating the neuroinflammatory response after TBI. Furthermore, H19‐KD promoted activation of the Nrf2/HO‐1 axis after TBI, while suppression of Nrf2 partially abolished the neuroprotective effect. Conclusion: H19‐KD exerts neuroprotective effects after TBI in mice, partially mediated by the activation of the Nrf2/HO‐1 axis. [ABSTRACT FROM AUTHOR]