Hi,
Im new to LS-DYNA and FEA, and have spent the last month getting familiar with the theory and UI of hypermesh and export in LS-PREPOST. My goal is to perform an impact analysis on a cfrp bicycle wheel. I'm not sure the best way to create the interface between spokes and the rim but my approach is to model the spokes with 3d elements, connect to the spokes and rim with surface to surface contact with the spoke hole closed, and an initial_stress_section applied to the spokes to model the pretension.
Before addressing this head on, I wanted to familiarize myself with setting up a composite simulation in LS-DYNA so I setup a custom plate and impactor. I haven't come across any full composite tutorials on youtube, so with the few i watched i have put something together using element_shell_composite method. After achieving normal termination, my simulation shows the plate expanding upon impact and not reacting with stability. I have attached an image showing the instability. If possible, am looking for some help in first debugging my test file.
So I’m not very familiar with modeling composites but I did gather together some materials that may help you here:
https://feassistant.com/forums/ls-dyna/composite-material-help/
I’m not sure of the exact application that you are wanting for the spokes and rim interface, so more information on this would be helpful. Is it an impact to the spokes? Regarding the spoke implementation, I would not use 3D solid elements if you are modeling the entire wheel, I’d use 1D beams and make it node to node with the rim. Let me know if this helps.
My goal is to assess the impact toughness of my rim design and optimize layup/stacking sequences. The spokes add stiffness to the overall structure of the wheel, and the pretension of the spokes act as springs for the wheel (higher the pretension, higher the equivalent spring stiffness).
Yeah I wouldn’t use 3D elements for the spokes if you main goal is to provide pretension. You can use *Element_Discrete which is a 1D element that you can define spring properties for the spokes. I would then spend most detail on the rim since that is the main part you are looking to model. There are so many different ways to connect the spokes to the rim but I’d first try a tied contact which transmits moments through the contact. I believe one is *Contact_Tied__shell edged_to_Surface_beam_offset. You read about more here:
https://www.dynasupport.com/howtos/contact/tied-tied-offset-and-tiebreak-contacts
Also, are you testing stability of this composite material in an isolated impact test? Is that the instability that you showed? It could purely be a mesh density/contact issue to why it's blowing up. What type of contact are you using?