Abstract
The measurement method on deformation and strain distribution at different length scales ranging from nm to mm was investigated by in-situ FE-SEM observation. The multiscale pattern fabricated by electron beam lithography technique has been developed to measure the localized deformation and strain distribution. The composite material used was ultrahigh strength PAN-based (IM600) and ultrahigh modulus pitch-based (K13D) hybrid carbon fiber reinforced epoxy matrix composites. Prior to in-situ loading, the multi-scale pattern was drawn onto the polished surface of the specimen. Electron moire method and digital image correlation method were applied to measure the multiscale deformation such as the fiber/matrix interface and the laminates interface acquired before and after loading. Delamination and the localized plastic strain clearly formed around the interfaces at different length scales. In the present study, the results clearly demonstrated that the development of a multi-scale pattern is significant for measuring multi-scale deformation and strain localization to identify damage initiation and evolution at different scale lengths.
