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RQsumB: La relation entre la vitesse de deformation et la resistance F la rupture interlaminaire en Mode II d'un composite lamink CF/epoxy a Bt B examine par des experiences en flexion d'un composite prQdelamin6 & son extremitk en mode dynamique (dynamic ENF test) utilisant l'essai SHPB. Les ondes incidentes de forme exponentielle ont Cvitk le problitme de vibrations parasites en flexion. L'analyse dynamique par les BlCments finis confirme que la formule estimee peut Btre utilisee pour la r'esistance F la rupture Mode 11, aussi bien en dynamique qu'en statique. Les rCsultats experimentaux montrent que la. rksistance F la rupture en Mode II a tendance B diminuer avec l'accroissement de la vitesse de deformation en cisaillement. Ceci serait dB aux diffkrences entre ruptures dynamique et statique.

To obtain the dynamic Mode II interlaminar fracture toughness of CFRP under impact loading, an impact bend test using split Hopkinson pressure bar (SHPB) method was applied to the end notched flexure (ENF) specimen, and the estimation of GII was investigated. The dynamic behavior of the ENF specimen during impact bending was analysed by the finite element method, and the history of the energy release rate GII of the specimen was calculated using the crack-closure method. The energy release rate GIICC calculated by the crack-closure method was compared with the energy release rate GIIST estimated by the formula for the static ENF test and the load history of the output bar of SHPB.The results obtained are as follows. For the step input loading, the ratio GIIST/GIICC oscillates strongly around unity and the oscillation continues after considerably long time, while for the ramp input loading with a finite rise-time, the oscillation is damped more quickly and the ratio G/G approaches to unity more gradually as the rise-time increases. Therefore, the dynamic Mode II fracture toughness can be estimated by the formula for the static ENF test if the ramp input loading wave with an appropriate rise time is applied.