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Dirk76

Contact problem with a composite plate

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Hi all, I'm encountering a problem in a low-velocity impact simulation with a composite plate. As you can see from the image below, at the beginning of the analysis, the impactor literally penetrates the plate but without effective failing of any elements. I experience this problem when I try to simulate the delamination, ply by ply (in my case 16 ply), using very thin shell elements (the thickness of each ply is approximately 0,23 mm). Indeed, after studying the contact problem in LS-DYNA, I figured out that, when very thin shell elements are used, the plate drastically fail when the impactor approaches it. For this reason I had to reduce the SLSFAC from 0.1 to 0.001 in *CONTROL_CONTACT in order to have reasonable results, because the impactor of only 1,5 kg and with an initial velocity of 6,5 m/s destroyed the plate in the very first milliseconds of the simulation without this change. But now, solved one problem (however I'm not really sure about this, maybe someone can explain me better this contact stiffness problem), I have another one :D I'm using a MAT22 model for the composite and a MAT20 for the impactor (made of steel). To simulate the delamination I chose the *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE_TIEBREAK with 15 delamination model in between, penalty contact SOFT = 0 (justified by the fact each ply is identical) and OPTION = 8 for the failure criteria (I didn't know if PARAM = CCRIT for this option had to be used, so I left it blank). For the contact between impactor and the plate I chose *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE with SOFT = 2 (because of the different materials and meshes), FS=FD=0,5 and with the impactor being the master and all 16 plies being the slaves. Any suggestions to solve this problem? Thanks in advance for any response.

 

 

impatto.bmp

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