EFFECT OF LOADING FREQUENCY AND INTERLEAF ON THE DELAMINATION CHARACTERISTICS OF LAMINATED COMPOSITES

In this study, the effect of loading frequency on delamination onset a nd growth characteristics of (30/-30(2)/30/90)(s)IM6/3501-6 laminates, with and without an interleaf was studied. FM 300 adhesive layers, ma nufactured by American Cynamid, were placed at the 30/90 interface to study the influence of interleaf on the delamination characteristics o f laminates. Quasi 3-D finite element analysis results indicate that t he maximum interlaminar normal stress is lower in the laminate with th e interleaf compared to the baseline laminate. Results also indicate t hat the presence of an interleaf reduces the Mode I component of strai n energy release rate at the critical interface. Experimental results indicate that the static delamination onset stress is greater in the i nterleafed laminate, but the ultimate failure strength of interleafed laminate is lower. The resistance to delamination growth is greater in the interleafed laminates under quasi-static loading. Under fatigue l oading the delamination onset life and growth rate of both baseline an d interleafed laminates were found to be frequency dependent. Fractogr aphic analysis of laminates reveals more hackles in interleafed lamina tes, indicating Mode II dominated failure. It was also noted that the matrix material exhibits greater ductility at lower loading frequencie s in laminates with and without the interleaf.