COMPRESSION BEHAVIOR OF FRP SANDWICH SPECIMENS WITH INTERFACE DEBONDS

Local regions of bond failure between face sheet and core are often ob served when sandwich structures are exposed to low energy impacts. Sim ilarly, impact loads frequently result in delaminations within the fac e sheets. In the absence of any delaminations in the sandwich structur e the buckling strain of the debonded region is in this work shown to be the key parameter in assessing the structural integrity of a sandwi ch component in compression. The objective of this study was to predic t the buckling of the debonded region and to investigate the parameter s controlling this instability. A large number of analyses of the dela mination buckling problem, which in many ways may appear similar to th e debond problem: have been carried out in the past. However, the debo nd-buckling problem has not been addressed before and as shown in this work there are significant differences. The Finite Element method was found able to predict all the experimentally observed phenomena accur ately. These calculations were expensive, and a simple one-dimensional closed form solution is proposed for qualitative parametric investiga tions. Effects of material properties and initial imperfections were e xamined. Analyses of the buckling of a delamination suggest that the e ffect of the core can be ignored. In contrast, the results presented i n this paper show that the core cannot be ignored in the case of buckl ing of a debond nor can it be simulated in terms of simple boundary co nditions.