fig7

Figure 7. (A) SEM images of GFRP fracture surface; (B) SEM images of GFRP embedded single PVDF film fracture surface; (C) Infiltration state of GFRP embedded single PVDF film fracture surface; (D) SEM images of GFRP embedded sandwiched-structure PVDF sensor fracture surface; (E) Infiltration state of GFRP embedded sandwiched-structure PVDF sensor fracture surface; (F) OM images of GFRP embedded sandwiched-structure PVDF sensor cross section. Crack propagation direction was from left to right.