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Because the physical properties of carbon fiber and glass fiber are very different, the fiber volume fraction in carbon/glass hybrid fiber composites cannot be tested by burning method or digestion method, respectively. Furthermore, these methods partially consume the fiber, especially for carbon fibers. To investigate the fiber volume fraction in carbon/glass hybrid fiber composites correctly, the test method is put forward. The burning method and the digestion method were combined to calculate the volume fraction of carbon fiber and glass fiber, respectively. The results show that the relative error between the measured value and the theoretical value is very small. The result of the present work implies that the feasibility and accuracy of this method through experimental verification. [ABSTRACT FROM AUTHOR]

In this article, the surface‐layer structure evolution of carbon fibers along the cross‐section γ‐irradiated in epoxy chloropropane has been estimated by X‐ray photoelectron spectroscopy combined with in situ argon‐ion sputtering that is different from argon‐ion cleaning. In argon‐ion (Ar‐ion) sputtering, the detection and sputtering were alternately in situ carried out. The penetration depth of irradiation medium on the surface of carbon fibers was accurately verified (13 nm) according to the absence of chlorine element and the change of O/C atomic ratio on γ‐irradiated carbon fiber surface. Such characterization technology has opened up a meaningful method to analyze the heterogeneous structure of materials. POLYM. COMPOS., 40:E832–E834, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The surface activity and mechanical properties of carbon fibers (CFs) were improved simultaneously by magical γ-irradiation. However, microstructure evolution rules of γ-irradiated CFs were still ambiguous. As a representative, T1000 CFs were irradiated by γ-rays and then observed by X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy from fiber surface, deducing the paradoxical results in terms of fiber structural transformation due to the different penetration depth of above measurements. Therefore, a hierarchical model composed of outer-surface, sub-surface and core parts had been proposed, which allowed us to understand the microstructure evolution of irradiated CFs profoundly. Subsequently, Raman spectra from fiber cross-section were performed to further confirm the accuracy of new model. The results demonstrated that oxygen-containing functional groups were significantly introduced into the outer-surface by the combined effect of γ-rays and reactive media, which increased the surface activity and disordered the structure of outer-surface part. Meanwhile, γ-irradiation improved the graphitic order and atomic rearrangement of sub-surface and core parts regardless of medium effect. Furthermore, the graphitization of sub-surface part showed more notable increase than that of core part under γ-irradiation. This paper would offer the key to reveal the relationship among microstructure, surface activities and mechanical properties of γ-irradiated CFs. [ABSTRACT FROM AUTHOR]

Repetitious sizing treatment was used to modify the carbon fiber (CF) surface with carbon nanotubes (CNTs) for improving interfacial properties of CF/epoxy composites. Interlaminar shear and flexural results showed that mechanical properties of composites were significantly depended on the dispersion state and contents of CNTs in interfacial regions. Increases of 13.45% in interlaminar shear strength and 20.31% in flexural strength were achieved in quintuple sized-CF/epoxy composites, whereas excessive CNTs led to decrease of interfacial performance due to defects induced by agglomerated CNTs. Energy dispersive X-ray spectroscopy and force modulation atomic force microscope were used to detect the structure of interfacial phase and results indicated that gradient interfacial structure with various thicknesses was formed due to CNT incorporation. This means that such a simple and efficient method to improve interfacial performance of composites via regulating the fiber–matrix interphase structure was developed and showed great commercial application potential. [ABSTRACT FROM AUTHOR]