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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., Article, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING. 42(7):703-711 (2011)

In the present paper, press molding for thermo-plastic resin toughened by carbon nanofiber were discussed. Polycarbonate (PC) and vapor grown carbon nanofiber (VGCF) are used for the resin matrix and the reinforcement. In order to investigate and simulate the molding process of the PC/VGCF composite by finite element method, the constitutive equation, namely thermo-viscoelastic property of the composites are required. The relaxation modulus (Master curve) and shift factor to characterize it's thermo-viscoelastic behavior were estimated by unidirectional compression creep test in this paper. The relaxation modulus for the composite were approximated by the discretized series form using generalized Maxwell model. The displacement history of the creep test were calculated by finite element method. The numerical and experimental results are compared and discussed in detail to confirm the validity of the estimated relaxation modulus obtained the present procedure.

In the present paper, press molding for thermo-plastic resin toughened by carbon nanofiber were discussed. Polycarbonate (PC) and vapor grown carbon nanofiber (VGCF) are used for the resin matrix and the reinforcement. In order to investigate and simulate the process molding process of the PC/VGCF composite by finite element method, the thermo-viscoelastic property of the composites are estimated using unidirectional compression creep test. The creep functions were converted into relaxation function based on the convolution integral form of the basic equation using Laplace transform. Experimental testing for press molding of the PC/VGCF composites using V-shape die has been carried out. The results of the V-shape profiles and those obtained by FEM analysis were compared to confirm the validity of the present analysis method based on thermo-viscoelastic theory. The effect of the carbon nanofiber for the formability improvement of the PC/VGCF composites was discussed in detail.