Hygroscopic aging cycles of bamboo fiber/epoxy composites: Comparative study between distilled water and sea water

Abstract

This paper explores the performances recovery of unfilled and montmorillonite (MMT)-filled bamboo fiber epoxy-composites when subjected to 7 hygroscopic cycles (up to 7 months) in distilled water and sea water environments. The influence of aging cycles on the moisture absorption, fracture surface and tensile properties of composites, is assessed. Attractively, their degradation mechanisms are analyzed using X-Ray diffraction (XRD), Infrared Spectroscopy (FTIR) and Scanning microscope (SEM), to understand the structural changes induced by the aging cycles. The main findings reveal that the cyclic aging in both environments, boosts the moisture gain of composites, mainly due to the active hydrolysis process at the fiber-matrix interfaces. More importantly, the unfilled bamboo fiber composites surprisingly show a perfect resilience to cyclic aging, which is attributed to the swelling/plasticization mechanisms as well as hydrolysis process. Infrared spectroscopy (FTIR) results confirm the dissolution of poorly crystallized components in the fibers after the aging cycles, allowing a better rearrangement of the cellulosic fibrils as shown by the XRD. However, a considerable fall in the tensile properties of composites filled with clay particles, is shown after the cyclic aging in both environments, due to the microstructural damage induced by the additional swelling of MMT fillers. Interestingly, the aging environment has no significant effect on the durability of bamboo fiber composites.