Influence of curved delamination front on toughness of multidirectional DCB specimens

Abstract

Mode I delamination toughness (G Ic) of a laminated composite depends not only on the stacking sequence or indirectly coupling parameter of Dc=D122D11D22, but also on specimen geometrical ratios a 0/b and a 0/h. In this study, a non-uniformity ratio, β=(G Imax-G Iavg)/G Iavg%, is introduced to take into account the influence of above factors on the energy release rate distribution along the width of double cantilever beam (DCB) specimens simultaneously. Results show that the G Ic of multidirectional DCB specimens with 0°//0° crack interface and β<20% can be predicted by measuring the G Ic of the unidirectional plies with an error less than 10%. Moreover, a methodology is proposed to predict the maximum delamination toughness (G Imax) of multidirectional DCB specimens from β parameter without performing any experiments. With the present method, the effect of curved thumbnail shape of energy release rate along the delamination front is considered on the available closed-form relations for G I. © 2011 Elsevier Ltd.