Estimating Fracture Toughness from Nonlinear Load-Deflection Relation

概要

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この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。Load- deflection relation of Double Cantilever Beam (DCB) specimens with thick epoxy adhesive layer was analyzed by assuming adherends to be elastic beam supported on a viscoelastic foundation. Method of analysis for the beam on elastic foundation was extended to the time dependent problem and numerical method based on the finite difference method was used. As the results of numerical calculations, it was clarified that while DCB specimen bonded with epoxy adhesives containing 0 and 20 phr of flexibilizer did not show the nonlinearity on load-deflection curve, those with 40 and 60 phr of flexibilizer showed the slight nonlinearity. Strain energy release rate of the DCB specimen was calculated from the load-deflection relation by employing the least squares method. Fracture toughness was estimated with experimental data and the derived equations of strain energy release rate. Other time independent methods for estimating fracture toughness of DCB specimen were also used, and results obtained by these all estimation methods were compared with each other. In consequence, no clear distinction between two kinds of fracture toughness estimated with time dependent equation and time independent equation was observed, because the relaxation time of epoxy adhesive was relatively large.
1976-10-30