Dynamic impact response of high-density square honeycombs made of TRIP steel and TRIP matrix composite material

Abstract

Abstract. Two designs of square-celled metallic honeycomb structures fabricated by a modified extrusion technology based on a powder feedstock were investigated. The strength and ductility of these cellular materials are achieved by an austenitic CrNi (AISI 304) steel matrix particle reinforced by an MgO partially-stabilized zirconia building up their cell wall microstructure. Similar to the mechanical behaviour of the bulk materials, the strengthening mechanism and the martensitic phase transformations in the cell walls are affected by the deformation temperature and the nominal strain rate. The microstructure evolution during quasi-static and dynamic impact compression up to high strain rates of 10 3 1/s influences the buckling and failure behaviour of the honeycomb structures. In contrast to bending-dominated quasi-isotropic networks like open-celled metal foams, axial compressive loading to the honeycomb's channels causes membrane stretching as well as crushing of the vertical cell node elements and cell walls. The presented honeycomb materials differ geometrically in their cell wall thickness-to-cell size-ratio. Therefore, the failure behaviour is predominantly controlled by global buckling and torsional-flexural buckling, respectively, accompanied by plastic matrix flow and strengthening of the cell wall microstructure.

Microstructural and Mechanical Characterization of Square‐Celled TRIP Steel Honeycomb Structures Produced by Electron Beam Melting

“…Main deformation stages of the displayed stress–strain curves (Figure ) are comparable with those of extruded square‐celled honeycomb structures made from commercial Cr–Ni–TRIP steel 1.4301 reported by Ehinger et al Initially, the cell walls are compressed elastically, which corresponds to a linear elastic stage. By exceeding the compressive yield strength, the structure's prebuckling stage initiates, which is characterized by a continuous rise of stress due to the strain hardening of the cell walls.…”

Buckling and crush resistance of high-density TRIP-steel and TRIP-matrix composite honeycombs to out-of-plane compressive load

“…The SHPB test setup ensured a stress-state equilibrium in the specimens (between the front and rear faces), a constant nominal strain rate, and a honeycomb deformation of up to 50%. More information about high strain rate testing on high-density square honeycombs is given in (Ehinger et al, 2012a). Furthermore, interrupted test runs were applied to study the buckling and failure evolution of the honeycombs in different deformation stages.…”

“…The increase in strength due to the strain-induced a'-martensite formation in the steel matrix (viz. the Transformation Induced Plasticity, or 'TRIP' effect) and the deformation constraints imposed by the embedded ceramic particles make important contributions to the honeycomb's crush resistance and energy absorption capability (Aneziris et al, 2009;Ehinger et al, 2012aEhinger et al, , 2011Ehinger et al, , 2012bKrüger et al, 2010).…”

Mechanical properties of high-density TRIP steel honeycomb structures with varying cell profiles under different loading conditions

“…Only a slight stress offset was evident between the Kagome and square-celled structures for dynamic strain rates, although the stress slope was comparable. However, by comparing the onset of the post-buckling stage, which is associated with structural bifurcation [15], lower strains and stresses were measurable for the square-celled structure. Similarly, the collapse strength was lower and collapse was initiated at lower stages of deformation.…”