Kenaf fibres demonstrate enormous potential in fibre reinforced composites with the excellent performance and environmental benefits. In this work, kenaf fibres were treated with NaOH at the concentrations of 1%, 2%, and 3%.Effects of the alkaline treatments on the mechanical properties of fibre and interfacial shear properties (IFSS) of the resulted composites were systematically evaluated. In addition, relationship between tensile strength and surface friction coefficient of kenaf fibre was shown. Relationship between tensile strength of fibre and IFSS of composites were explored. They were conducted by correlation analysis method. The results indicated that after NaOH treatment, kenaf fibres has increased in tensile strength, surface roughness, friction coefficient, but decreased in diameter. Tensile properties, flexural properties and water absorption of unidirectional kenaf fibre reinforced epoxy resin composites have improved. IFSS of composite treated at 2% alkali has increased by 10.34%, compared to composites untreated fibres. Correlation analysis indicated that there was no significant correlation between kenaf fibre tensile strength and IFSS of the composite. On the other hand, there was significant correlation between kenaf fibre surface friction and the IFSS of the composite with the correlation coefficient of 0.905. ABSTRAK Serabut kenaf menunjukkan potensi besar dalam pembuatan komposit diperkuat serabut disebabkan ia mempunyai prestasi cemerlang dan kesan positif kepada alam sekitar. Dalam kajian ini, serabut kenaf dirawat dengan natrium hidroksida (NaOH) pada kepekatan 1%, 2% dan 3%. Kesan rawatan alkali terhadap sifat mekanik serabut dan sifat geseran permukaan (IFSS) daripada komposit yang dihasilkan dinilai secara sistematik. Di samping itu, hubungan antara kekuatan tegangan dan koefisien geseran permukaan serabut kenaf telah dinyatakan. Hubungan antara kekuatan tegangan serabut dan IFSS komposit telah diterokai. Analisis dijalankan melalui kaedah analisis korelasi. Keputusan menunjukkan selepas rawatan NaOH 1%, serabut kenaf meningkat dalam kekuatan tegangan, kekasaran permukaan, koefisien geseran dan penurunan diameter. Sifat tegangan, sifat lentur dan penyerapan air komposit resin epoksi diperkuat serabut menunjukkan peningkatan. IFSS komposit dengan serabut yang dirawat dengan 2% alkali meningkat sebanyak 10.34%, berbanding komposit dengan serabut yang tidak dirawat. Analisis korelasi menunjukkan tiada korelasi yang ketara antara kekuatan tarik serabut kenaf dan IFSS komposit. Sebaliknya, terdapat hubungan yang signifikan antara geseran permukaan serabut kenaf dan IFSS komposit dengan koefisien korelasi sebanyak 0.905.
Ramie fabric-reinforced thermoset polylactic acid (PLA) composites were prepared by using heat pressing technology. Fabrics were treated with alkali, silane, and alkali–silane respectively, expecting an improvement of the interface between the fabric and the matrix. Scanning electron microscopy (SEM) results indicated that after alkali treatment, impurities on the fiber surface were removed and its diameter became finer. After the silane, and alkali–silane treatments, the contact angles of the ramie fibers increased by 14.26%, and 33.12%, respectively. The contact angle of the alkali–silane treated fiber reached 76.41°; this is beneficial for the adhesion between ramie fiber and the PLA. The research revealed that the tensile strength of the fiber increased after the alkali and silane treatments. A slight decrease was noticed on the tensile strength of fibers treated with alkali–silane. After all, three chemical treatments were done, the flexure strength of the ramie fabric-reinforced PLA composites, improved in all cases. Among the three treatments, the alkali–silane treatment demonstrated the best result, as far as the flexure strength and modulus of the fabricated composites were concerned. On the other hand, water absorption of the related composites decreased by 23.70%, which might contribute to the closer contact between the ramie fiber and the matrix. The ramie fabric-reinforced PLA composites, prepared in this study, can meet the standard requirements of aircraft interior structures and have favorable application foreground.
Background: Pericoronary adipose tissue (PCAT) and Coronary Artery Disease Reporting and Data System (CAD-RADS) category had prognostic values for major adverse cardiovascular events (MACEs). However, little is known about the difference between CAD-RADS and PCAT computed tomography (CT) attenuation for predicting MACEs. This study was to compare the prognostic value of PCAT and CAD-RADS for MACEs in patients with acute chest pain. Methods: Between January 2010 and December 2021, all consecutive emergency patients with acute chest pain referred for coronary computed tomography angiography were enrolled in this retrospective study. MACEs included unstable angina requiring hospitalization, coronary revascularization, nonfatal myocardial infarction, and all-cause death. Patients’ clinical characteristics, CAD-RADS, and PCAT CT attenuation were used to evaluate risk factors of MACEs using multivariable Cox regression analysis. Results: A total of 1313 patients were evaluated (mean age, 57.13±12.57 years; 782 men). During a median follow-up of 38 months, 142 of the 1313 patients (10.81%) experienced MACEs. Multivariable Cox regression analysis showed that CAD-RADS categories 2, 3, 4, 5 (hazard ratio range, 2.286–8.325; all P <0.005) and right coronary artery PCAT CT attenuation (hazard ratio, 1.033; P =0.006) were independent predictors of MACEs after adjusting for clinical risk factors. The C statistics revealed that CAD-RADS improved risk stratification compared with PCAT CT alone (C-index, 0.760 versus 0.712; P =0.036). However, the benefit of right coronary artery PCAT CT attenuation combined with CAD-RADS was not significant compared with CAD-RADS alone (0.777 versus 0.760; P =0.129). Conclusions: Right coronary artery PCAT CT attenuation and CAD-RADS were independent predictors of MACEs. However, no incremental prognostic value of right coronary artery PCAT CT attenuation beyond CAD-RADS was detected for MACEs in patients with acute chest pain.
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