DELAMINATION INITIATION PREDICTION FROMCONSTITUENT BEHAVIOR

摘要

There is currently no method available to determine the delamination toughness of a compositefrom its constituents’ properties. This is an important link that could help accelerate the insertion ofmaterials via an analytical process that connects material behavior at various lengthscales. A finiteelement model is created to investigate the contribution of inelastic deformation at the crack tip in acomposite double cantilever beam specimen to the composite toughness. The constituent properties areexplicitly incorporated into the analysis through the use of a global-local model. The global J-integral isrepresentative of an experimentally determined fracture toughness while the local J-integral accounts forinelastic deformation at the crack tip. Fracture measurements are carried out on IM7/977-3 and its neatresin in order to obtain data for incorporation into and comparison with the model. In addition, theexperiments allow for determination of the important fracture mechanisms. The model is interrogated byvarying the plastic behavior of the resin and the constraint on the resin. Using the neat resin fracturetoughness as a local fracture criterion is found to be inadequate, but data on constrained resin behaviormay be used. The tool is useful for evaluating candidate resin and fiber systems if the resin inelasticbehavior is known and an estimate of the constrained resin toughness can be made. Data from adhesivebond tests using neat resins with thin layers on the order of the interply resin thickness could be used asan estimate of composite toughness while the model could be used to explain the differences between theneat resin and composite toughnesses.