Investigation of the performances for CFRP composites exposed to different aging environment at nano-scale

The nanomechanical technique was applied to investigate quantitatively the evolution of epoxy matrix and fiber/ matrix interface in CFRPs under different hygrothermal conditions (water, seawater and acidic solution at 20, 50 and 80 C). The moisture penetration depth was originally defined based on the change trend of nanoindentation hardness and elastic modulus from the exposed surface to the center area of sample. The scanned modulus map of composite surface using Peak Force Quantitative Nano-mechanic (PF-QNM)) method was used to deduce the interface thickness. It was found that the moisture uptake of CFRPs in water was higher than that in seawater, but lower than that in acidic solution at the same temperature. High temperature promoted the penetration of water molecules. The moisture penetration depth was about 600 mu m for the composites reaching the saturation moisture uptake in the deionized water and seawater at 80 C, but 800 mu m for the composites in the acidic solution. The interface thickness was enlarged with the moisture uptake increasing in water and seawater, which was attributed to the plasticizing effect of water molecules, whereas the acidic solution produced an inverse trend, which might be due to the secondary crosslinking reaction of free radicals.

Automated summary

The evolution of epoxy matrix and fiber/matrix interface in CFRPs under different hygrothermal conditions was quantitatively investigated using a nanomechanical technique. It was found that CFRPs had higher moisture uptake in water compared to seawater, but lower than that in acidic solution at the same temperature. High temperature promoted the penetration of water molecules. The interface thickness increased with the moisture uptake in water and seawater, but showed an inverse trend in acidic solution.