Figure 7
(a) Loading–unloading curve of the epoxy sample embedded with a single carbon fiber. The gradual increase in residual displacement after unloading implies the progress of the interfacial debonding. (b) Optical images observed under high-magnification microscope before and after unloading with an increment of 10 MPa until fracture. The lower and upper images were captured before and after unloading at each loading cycle, respectively. The dark boundary zone became gradually thicker at the higher loadings, and confirming the interfacial debonding by observing the sample surface was difficult.
