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

Abstract

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 μm for the composites reaching the saturation moisture uptake in the deionized water and seawater at 80 °C, but 800 μm 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.

Keywords

• Carbon fiber reinforced epoxy composites
• Hygrothermal aging
• Nanomechanical techniques
• Moisture uptake
• Interface thickness