I try to simulate tensile test on hybrid ALUMINIUM/GLASS/CARBON fiber reinforces polymers using VUMAT composite subroutine with Hashin 3d failure criteria in ABAQUS Explicit. Generally, the elastic range of hybrid structure is working very well. Thermal stresses are visible and corresponds with theoretical calculations performed by Classical Laminate Theory.
The problem is with Hashin 3d failure criteria after tensile fracture of CFRP part. In ABAQUS Explicit analysis controlled by displacement, after CFRP failure (for about 1.5% of elongation) the GFRP part also fails immediately, which is different than in experimental tests (the GFRP part fails for about 3.5 % of elongation). What is the reason for immediate deleting both CFRP and GFRP elements, despite the GFRP part should withstand specified displacement and fail later?
I use 10 mm displacement and smooth amplitude step. Is anybody can give me some advice, how to obtain the convergence solution?
First of all, despite the difference of final elongation for carbon fiber and glass fiber, the carbon fiber is stiffer and most of the loading are supported by this material. After carbon fiber failure, you have a stress redistribution that could (not necessary, depends on the boundary conditions), results in a very high loads for glass fiber part and it could not support it.
Other possible cause is your fem model. How you are dividing the model, element type, time integration length, mesh refinement, etc. It is not easy to answer your question without know your model and what are you trying to model (real structure).
Regrads
I consider there might be two reasons:
1. The time was set too short so that the analysis was not completely quasi-static. Try to increase the time.
2. The interface between CFRP and GFRP layer were modelled by using shared nodes method. You can try to use cohesive elements to define these interfaces.
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