dear sir

this may be help you

Numerical analyses of low velocity impacts on composite. Advanced modelling techniques.

Giovanni Perillo1, Nils Petter Vedvik1, Andreas T. Echtermeyer1

1 Norwegian University of Science and Technology (NTNU) - Department of Engineering Design and Materials

best reqards

Dear Dr Nabel,

Many thanks for your suggestion. Actually, I read all these papers and I'm struggling just with Force-displacement plots.There is no agreement with experimental graphs.

Couple of suggestions/comments:

1- How do you extract the force/displacement from your model? Is it just a single element/node? integration of volume elements? a reference node?

2- If the simulation differs from experimental results, you should check your boundary conditions, the damage initiation and damage constitutive laws .

I hope this helps

Thanks so much Dr Mohamed. Actually, I extracted the Force-displacement plots for refercence node by combine Force-time and Displacement -time togeter and then finally I got Force-diplacement graphs. According to your suggestion I will try to change the boundry conditions of lamainates and hopfully I will find new things.

Just make sure the boundary conditions in your model represent the actual boundary conditions you have in your experimental setup.

Its tough to tell when you are simulating impact. I believe you are capturing damage in composites (intra and inter), For inter laminar analysis, the parameters for the cohesive elements needs to be paid attention such as Knn, Kss and Ktt and may others. For Intra laminar, if you are using Hashin, the strength values inputted are critical. Check these values. Since you mentioned difference from Experimental values, I believe this is the only reason , the values inputted for Cohesive elements and Hashin might not be in accordance to experiments.