Comparison of LS-DYNA and NISA in Solving Dynamic Pulse Buckling Problems in Laminated Composite Beams

In this paper the dynamic pulse buckling of laminated composite beams was analyzed using LS-DYNA and another widely used commercial FE code, namely NISA (Ver.12), developed by EMRC (Engineering Mechanics Research Corp). Two types of impact loadings that could induce dynamic pulse buckling of composite beams were analyzed. The first one was a force applied to the structure in a very short duration (i.e., an impulse load). The other one was the impact of a moving mass having a certain initial velocity. This problem brings considerable challenges if one is to simulate the phenomenon accurately. The main objective of this technical exercise was to investigate the influence of certain numerical parameters on the integrity of the out coming results. The objective was also to assess the performance of a “conventional, general purpose” type FEM program versus LS-DYNA, which is considered as a leading FEM code for the analysis of highly nonlinear phenomena. This was an interesting exercise in demonstrating why one should use codes like LS-DYNA, as oppose the general purpose FEA codes when considering such highly non-linear phenomena. Both abovementioned loading types were considered in this study. In the analysis using LS-DYNA, the force function was introduced by applying an impulse force at one end of the FRP beam. The moving object was also modeled in LS-DYNA by means of a rigid wall having a mass and an initial velocity. The impact by moving object could not be accommodated by NISA, so only the pseudo-impulse type loading could be considered in NISA. Parametric studies were also conducted to investigate the effect of the slenderness ratio, the curvature and the stacking sequences of the FRP beams, as well as the examination of the influence of the initial imperfection used to promote structural instability.