I wish to simulate snap-through of thin curved composite shells and thin doubly curved composite shells under forced vibration. I have read the section on "Choosing a shell element" in the ABAQUS Analysis User's Manual and understand that my options are S4, S4R, S8R5 and S9R5. The section recommends the use of S8R5 or S9R5 for bending of thin curved shells, and S9R5 for buckling of thin doubly curved shells. It is my understanding that S9R5 elements cannot be used directly in ABAQUS/CAE and the input file must be edited to use S9R5 elements. What is the process for doing this?

Additionally, I would like to request the advice of more experienced users as to what element type I should use? Research papers I have read that have simulated snap-through under forced vibration of initially flat unsymmetric composite laminates with curvature then developed as a result of residual thermal stresses from cure have used S4R elements. Would this be a suitable element to use and give accurate results for this scenario, and also for thin composite shells with initial double curvature? Thank you.