Hierarchical Interfacial Construction by Grafting Cellulose Nanocrystals onto Carbon Fiber for Improving the Mechanical Performance of Epoxy Composites.

Carbon fiber-reinforced composites have been widely used in the aerospace industry because of their superior comprehensive performance, including high strength, low density, fatigue resistance, long service life, etc. The interface between the fiber reinforcement and the matrix is one of the key factors that determines the performance of the composites. The construction of covalent bonding connections between the components has proven to be an effective strategy for improving the interfacial bonding strength but always reduces the toughness. In this work, dual silane coupling agents are applied to covalently connect cellulose nanocrystals (CNCs) onto carbon fibers, constructing hierarchical interfacial connections between the fibers and the epoxy matrix and significantly improving the interfacial bonding strength. As a result, the tensile strength of the epoxy composites increased from 519 MPa to nearly 900 MPa, which provides a potential approach for significantly improving the mechanical performance of composites.

Interfacial Enhancement by CNTs Grafting towards High-Performance Mechanical Properties of Carbon Fiber-Reinforced Epoxy Composites.

The problem of interfacial interaction between carbon fiber (CF) and the matrix is the key to the failure of CF-reinforced plastic (CFRP). A general strategy to enhance interfacial connections is to create covalent bonds between the components, but this usually reduces the toughness of the composite material, which in turn limits the range of applications of the composite. In this study, carbon nanotubes (CNTs) were grafted onto the CF surface using the molecular layer bridging effect of the dual coupling agent to prepare multi-scale reinforcements, which significantly improved the roughness and chemical activity of the CF surface. By introducing a transition layer structure between the carbon fibers and the epoxy resin matrix to moderate the large modulus and scale differences between them, the interfacial interaction was improved while enhancing the strength and toughness of CFRP. We used amine-cured bisphenol A-based epoxy resin (E44) as the matrix resin and prepared the composites by the hand-paste method and performed tensile tests on the prepared composites, which showed that, compared with the original CF-reinforced composites, the modified composites showed an increase in tensile strength, Young's modulus and elongation at break by 40.5%, 66.3% and 41.9%, respectively.

Analysis on geographic variations in hospital deaths and endovascular therapy in ischaemic stroke patients: an observational cross-sectional study in China.

OBJECTIVES: Stroke is the leading cause of death and adult disability in China, following a rise in incidence over the last few decades. We aimed to explore the geographic variations in hospital mortality and endovascular therapy (EVT) use among ischaemic stroke (IS) patients in China, and investigate the associated potential risk factors. DESIGN: Observational cross-sectional study of patients hospitalised for stroke. SETTING: Hospital discharge data for 1267 tertiary hospitals between 1 January 2015 and 31 December 2015 were derived from the Nationwide Hospital Discharge Database operated by the National Health Commission of China. PARTICIPANTS: 1 826 332 patients aged ≥18 years, hospitalised following stroke. OUTCOME MEASURES: In-hospital mortality and EVT use. RESULTS: The nationwide hospital mortality rate of IS patients was 0.88% (95% CI 0.86% to 0.90%); there was a significantly greater risk of mortality in the Northeast (OR 2.37; 95% CI 2.23 to 2.52), West (1.65; 1.54 to 1.78), South (1.25; 1.17 to 1.33) and North (1.29; 1.20 to 1.39) than in the East. Tertiary B hospitals (OR 1.05; 95% CI 1.00 to 1.09), patients admitted from emergency departments and older patients were associated with higher hospital mortality. The national EVT use rate was 0.45% (95% CI 0.44% to 0.46%). Compared with in East China, EVT use was significantly lower in the Northeast (OR 0.22; 95% CI 0.20 to 0.24) and West (0.64; 0.58 to 0.71), though not the North (1.23; 1.14 to 1.33). Tertiary A hospitals (OR 2.62; 95% CI 2.43 to 2.83), male patients and patients admitted from emergency departments were also associated with higher EVT use rates. CONCLUSIONS: There were substantial disparities in mortality and EVT use for hospitalised patients with IS among China's tertiary hospitals, linked with both geographic and hospital characteristics. More targeted intervention at regional and hospital levels is needed for providing effective health technologies and eventually improving post-stroke outcomes.