Mode I interlaminar fracture of composite laminates incorporating with ultrathin fibrous sheets

Attempts have been made to investigate the effect of ultrathin fibrous sheets (UFSs) arranged on the ply interface on mode I interlaminar fracture of a glass/epoxy composite laminate. The UFSs were obtained by electrospinning of epoxy 609 polymer solution and then incorporated into the middle interface of the laminate with various thicknesses. Mode I interlaminar fracture behaviors of the resulting laminates were characterized using double cantilever beam (DCB) specimens. Scanning electron microscope (SEM) was applied to analyze the fracture characteristics of the tested specimens. Results have shown that the UFS with a reasonable thickness would have no effect on the mode I delamination resistance of the laminate. To further investigate the effect of the sheets on the fracture toughness, some UFSs with thinner thickness were inserted into different interfaces of the laminate. Testing data have also shown that no significant effect on the mode I delamination resistance was recognized, although a summation of the sheets was thick. Fractured specimens analysis indicated no obvious delamination was observed when the incorporated sheet was thin.