A composite material can be defined as a combination of a matrix and a reinforcement, which when combined gives properties superior to the properties of the individual components. Due to composite material’s potential, they can be comprehensively used as a suitable replacement for steels and aluminum with better operation. Nowadays, composites have a wide usage; hence, behavior investigation and protecting them in various situations are significant issues. Metals can absorb energy by elastic-plastic deformations in low energy impacts which cause some permanent deformations in structure. However, composites exhibit low plastic deformatio most of the absorbed energy spends to form damage zones. Therefore, strength and stiffness reduction occurs. Thus, Energy absorber utilities are great solutions for impact damage protection. In this study, number of honeycomb layers that needed to protect composite beam from defined impact energy has been investigated. In current research, glass-polyester channel section pultruded beam and nomex honeycomb are used. In order to assess impact damage effect on axial-buckling strength, axial strength of intact and impacted beam were measured. After that, effect of using honeycomb layers on damage and axial-buckling strength reduction has been investigated. Simulations were done in finite element software ABAQUS/Explicit. First, honeycomb mechanical properties were extracted from representative volume element (RVE) simulations and compared with flatwise compression test results. Then, loading rate effect on honeycomb properties was studied. At last, extracted properties were assigned to a solid part as an energy absorber. For modeling damage initiation and defining material orthotropic behavior, user subroutine VUMAT was utilized. In order to investigate damage initiation, maximum stress and Hashin failure criteria and instantaneous damage evolution law were used. Simulations verified by experimental tests. Number of honeycomb layers that prevent damage initiation in beam was investigated; simulation indicated that 3 layers of honeycomb protect the beam from impact. With the aid of this study, mechanical properties of other honeycombs can be extracted by RVE simulation without any experimental test cost. Also, another honeycomb with similar geometry and different wall thickness was modeled. Result showed that one layer of this honeycomb prevents damage in beam. Keywords : Energy absorber, Nomex honeycomb, RVE, Axial impact, FE analysis, VUMAT subroutine, Experimental test.
