An Investigation on Nanocomposites Damage Tolerance

摘要

It is a well known fact that, nanocomposites are a special class of composite materials. To be able to investigate the damage tolerance of this class of composite materials, two strategies were employed. The first one was to use of the Split Hopkinson Pressure Bar (SHPB). In addition to the SHPB tests, low velocity impact tests were also performed. The fiberglass used was in a plain weave configuration with density of 6 oz/yd~2 , while the epoxy system was supplied by Hunstman Inc. (RemLam M+HY956). The nanoparticles used were from Southern Clay (Cloisite 30B) and Nanocor (Nanomer I30E), while the nanographite with surface modification was supplied by Nacional Grafite. The fiber volume fraction was kept constant and equal to 65%, while the nanoclays employed were 5 wt% and 10 wt%. The optimum condition selected for the nanographite was 3 wt%. The dynamic stress-strain curves showed significant nonlinearity and strain-rate sensitivity. It seems that nanoclayanographite content and its nano-structures (intercalated) can also influence the composite behavior. Stiffness seems to be directly proportional to the nanoclay content. An increase on strain rate can lead to a correspondent increase on stiffness. The main failure mechanism changed from fiber breakage to delamination with the dispersion of nanoclay and nanographite. The 3% nanographite condition performed even better than the optimum nanoclay condition (5%). The damage tolerance (capacity of sustain damage with a catastrophic failure) increased approximately 9% with a 5 wt% nanoclay dispersion and close to 42% with the 3 wt% nanographite addition.