A study on nanostructured laminated plates behavior under low-velocity impact loadings

The influence of montmorillonite (MMT) silicate layers on glass-fiber-epoxy laminated composites behavior has been investigated by low-velocity impact and X-ray diffraction tests. The glass-fiber-epoxy-nanoclay laminate composites have 16 layers and 65% fiber volume fraction is manufactured by vacuum-assisted wet lay-up. Fibers have a plain-weave configuration with density of 200 g/m(2), while the epoxy resin system is made of diglycidyl ether of bisphenol A resin with aliphatic amine as the curing agent. The nanoclay (Nanomer I30E) is dispersed into the epoxy system in a 1%, 2%, 5% and 10% ratio in weight with respect to the matrix. X-ray diffraction tests indicate that rather than exfoliated, these nanostructures are mostly in intercalated form, with a possible presence of immiscible nanosystems at 10% concentration. The methodology used for the impact test is based on the ASTM D5628-01 standard. The results have shown that for the four edges clamped condition not only the delamination phenomenon is reduced, but also the damping is increased during the rebounds. Moreover, for the 20J impact energy condition the energy absorption by delamination increases close to 48%, while for larger energies, i.e. 60J, the average improvement into energy absorption is around 15%. Even for larger energies close to total perforation, i.e. 80J, the use of nanoclays leads to an average increase in energy absorption by delamination close to 4%. Finally, the failure mechanism seems to be affected by the nanoclay presence, as the interlaminar failure shifts to a mostly intralaminar failure with the increase of nanoclay content. (C) 2006 Elsevier Ltd. All rights reserved.