Criterion for interlaminar strength of CFRP laminates toughened with carbon nanofiber interlayer

The criterion for the interlaminar strength of unidirectional carbon-fiber-reinforced plastic (CFRP) laminates is discussed. To evaluate the limit curve given by the relation between normal stress and shear stress on the fracture interface, two types of interlaminar strength tests were carried out using short beams of CFRP laminates. The criterion for the interlaminar fracture of the CFRP laminates was investigated in two-dimensional finite element analysis of the CFRP specimens. Interlayers made by carbon nanofiber were inserted between the prepregs of the CFRP laminates. A modified ‘Tsai–Wu’ criterion was employed to evaluate the critical curve of the interlaminar fracture of the CFRP laminates. The effect of the CNF interlayer on the criterion of the interlaminar strength of CFRP laminate is discussed in detail.