Numerical Simulation Of Crack Damage At Face/Core Delamination Front In Sandwich Structure

Sandwich structures are made of thin and stiff face sheets and weaker core. Theupper and lower face sheets are bonded to the core by glue.In practice, There arealways face/core debonds exists in sandwich structure. These debonds are usuallyinduced during manufacturing or by hard object impact during service. The presenceof a face/core debond is most severe for a sandwich structure loaded in compression.It decreases the load bearing ability and the life of the structure drastically andprobably leading to heavy accident. A compression loaded panel containing asufficiently large debond may fail by local face sheet buckling over the debond, andthe debond may propagate further leading to undesired outcome. So it has a greatmeaningtopredictthepropagationofthedebond.The purpose of this paper is to predict the mechanical behavior and thepropagation of the debond of a compression loaded panel containing a face/coredebond. During the research, we used the FEA software to simulate the mechanicalbehavior and the propagation of the debond of the compression loaded panel. Thisresearch concentrates on the simulation of panels with circular debonds, ellipticaldebonds and through-width debonds. We simulate the glue with three sets of springelements. Two sets tangent to the face and the other set normal to the face sheet. Wefoundthatforcirculardebondandellipticaldebondwiththeratioofshort axistolongaxisgreaterthan0.5,thedebondbegantopropagatefromthetransversaldelaminationfront. But for the elliptical debond with the ratio of short axis to long axis smaller orequal to 0.5 and greater than 0.15, the debond began to propagate from the tip of theshort axis. For the elliptical debond with the ratio of short axis to longaxis smaller orequal to 0.15, the sandwich structure buckles overall before the debond propagates.For the one-dimensional through-the-width debond, the debond propagation loaddecreases as the width of the debond becomes larger. For debonds with arbitraryshapes, the debond propagation load lowers with the debond area increases. As theradiusofthecirculardebondreducesto15mm,thesandwichstructurebucklesoverallbefore the debond propagates. Compared with the experimental results and thosecomputed by enegy release rate, we proved the reasonability of the results. We alsodiscussed the choose of debond propagation criterion and found that the criterion weused in this paper operates easily and has higher precision.We studied the effects of thedebondsize,theparameters andmoduleofthefacesheet,thecoreandtheglueonthe propagation load and mechanical behaviors. During the research, we found andsummarized some rules and tendencies, provided some useful accordings to furtherandsubsequentresearch.