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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.

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.

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]

High performance carbon-reinforced composite materials have become important aeronautical materials. During the service time, the delamination fracture of composite structures is a common failure mode. In this study, in order to investigate the delamination behaviours of T800/epoxy composite materials under different mixture ratios, DCB, ENF and MMB tests were conducted on composite laminates with pre-set 0°/45° interface respectively. From the test, the initial delamination fracture toughness and delamination growth behaviour were obtained. The test results show that the fracture toughness and delamination behaviour are significantly affected by the mixture ratio. With the increase of mixture ratio, the fracture toughness increases, and steady delamination growth behaviour is more difficult to maintain. Based on the data fitting method, a prediction function for fracture toughness of the 0°/45° interface at arbitrary mixture ratio is established, which has some engineering values.