Acoustic emission characterization of damage in short hemp‐fiber‐reinforced polypropylene composites

This article aims at investigating the effects of hygrothermal aging on the damage mechanisms of short white Hemp Fiber Reinforced Polypropylene (HFRP) composites with various fiber contents (10, 20, 30, and 40 wt%). Injected molded specimens were subjected to hygrothermal aging with a relative humidity of 80% and two temperatures, 25 and 50°C. The water absorption and its effect on tensile properties of HFRP composites were investigated. The Acoustic Emission (AE) technique combined with scanning electron microscopy observations was used to identify microstructural damage events leading to overall failure of the HFRP composites. This identification according to hemp‐fiber content and hygrothermal aging was made with an unsupervised method based on a statistical multi‐variable analysis (k‐means algorithm). The AE results indicate that the quality of fiber‐matrix interface plays a major role in the damage process of HFRP composites, shown by the number of AE signals induced by the interface failure and their amplitude ranges. POLYM. COMPOS. 37:1101–1112, 2016. © 2014 Society of Plastics Engineers     

Ultraviolet radiation aging impact on physicochemical properties of crosslinked polyethylene cable insulation

This article deals within the study of the effect of artificial radiations on physical and chemical properties of the crosslinked polyethylene (XLPE) material, widely used for manufacturing high-voltage cables. Within this framework, several experimental tests, using essential characterization techniques, were performed to study XLPE behavior under ultraviolet (UV) aging. Attenuated total reflection Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy were thus carried out to identify the main structure changes of the material before and after exposure to UV. In addition, appearance changes and DC (Direct Current) volume resistivity were evaluated. The obtained results showed that UV radiation has a great effect on the physicochemical properties of XLPE cable insulation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48575.