Compressive behaviors and morphological changes of resorcinol-formaldehyde aerogel at high strain rates

The dynamic compressive properties of resorcinol-formaldehyde (RF) aerogel were investigated using a spilt Hopkinson pressure bar. The effects of strain rate, water absorption and sample basal area on the dynamic behaviors of RF aerogel were investigated through a series of dynamic experiments. Morphological changes of RF aerogel under compression were studied by SEM, TEM, BET and BJH methods. Results show that the compressive behaviors of RF aerogel display a remarkable strain rate strengthening effect. The water-saturated RF aerogel shows stiffened behavior at high strain rates in comparison with the dry RF aerogel, but the dynamic failure strain is small. The dynamic compressive behaviors of RF aerogel display a remarkable size effect. The stress increases with the sample basal area at the same strain. At high strain rates, the pores shrink rapidly; RF particles fuse together to form larger particles and surface area reduces rapidly. It is the fusing of gel particles that allows RF aerogel to be much more ductile than silica aerogels and not to break into fragments at high strain rates. (C) 2010 Elsevier Inc. All rights reserved.