Mode I interlaminar fracture characteristics of CNTs doped woven and unidirectional CFRP via acoustic emission.

• The delamination behavior of CNTs with different contents in PW and UD fabric composites is investigated. • The initial and propagation fracture toughness are calculated through the modified beam theory. • The acoustic emission signals of different damage mechanisms are distinguished. • The weakening and enhancing mechanisms are revealed by observing the surface photomicrograph. This paper investigates the delamination behavior of two composite structures with carbon nanotubes (CNTs). Double cantilever beam (DCB) samples with CNTs of different areal densities are adopted to analyze the toughening and damage mechanism via acoustic emission (AE) method. The result demonstrates that the CNT layer improves the fracture toughness of unidirectional (UD) sample interfaces effectively, but for the plain woven (PW) samples, only works on initial fracture toughness with low CNTs areal density. In addition, more AE events are recorded in the CNT modified samples than in the reference sample. Combined with the observation of the fracture surface and crack propagation path, the agglomeration with high content CNTs weakens the interlayer strength in PW samples, whereas the fracture toughness is significantly enhanced in UD composites due to the increase of the crack propagation path. [ABSTRACT FROM AUTHOR]