Impact loading and modelling a multilayer aluminium corrugated/fin core: The effect of the insertion of imperfect fin layers

Abstract

The quasi‐static compression (0.0048 m/s) and Taylor‐like impact (135, 150, and 200 m/s) loading of a multilayer 1050 H14 aluminium corrugated core were investigated both experimentally and numerically in LS‐DYNA using the perfect and imperfect sample models. In the imperfect sample models, one or two layers of corrugated fin structure were replaced by the fin layers made of bent‐type cell walls. The localised deformation in the quasi‐static imperfect models of cylindrical sample started at the imperfect layers, the same as the tests, and the layers were compressed until about the densification strain in a step‐wise fashion. The localised deformation in the perfect models, however, started at the layers at and near the top and bottom of the test sample. In the shock mode, the sample crushed sequentially starting at the impact end layer regardless the perfect or imperfect sample models were used. Furthermore, the perfect and imperfect models resulted in nearly the same initial crushing stresses in the shock mode. The layer strain histories revealed a velocity‐dependent layer densification strain. Both model types, the imperfect and perfect, well approximated the stress‐time histories and layer deformations of the shock mode. The rigid perfectly plastic locking model based on the numerically determined densification strains also showed well agreements with the experimental and numerical plateau stresses of the shock mode.

Impact loading of functionally graded metal syntactic foams

“…In the impact tests, the cylindrical FG-MSFs samples were directly impinged with the desired initial velocity of either 55 or 175 m/s. The applied impact tests in this study are very similar to the Taylor impact test setup [24] and the corresponding bar is named as incident bar for this configuration. This type of impact test is a non-equilibrium test to investigate the development of shock stress in cellular materials.…”

“…3, u is the displacement, h is the length of the densified region, x is the uncrushed length, x o is the initial length of the crushed region, ρ is the density of the crushed region, ρ o is the initial density, l o is the initial length, ε d is the densification strain, and v o is the initial velocity. The following relation applies to the initial and crushed section density as [24]:…”

“…The initial crushing stress can be determined by applying mass and momentum conservations between crushed and uncrushed section and Newton's second law to the uncrushed section give the crushing stress as [24]:…”

“…where v(t) is the velocity of the sample. The variation of velocity with time can be determined by applying Newton's second law to the uncrushed section [24]:…”

“…In the present study, this initial average strain rate N. Movahedi et al limit is exceeded by the impact velocity of 175 m/s (5833 s − 1 ), while a slightly lower initial average strain rate is obtained for the samples tested at 55 m/s (1833 s − 1 ). The deformation behaviour of cellular metals at higher strain rates is usually classified according to two different mechanisms named transition and shock deformation modes [15,24]. In both cases, the deformation originates from the impact front of the material regardless of the position of its weakest section (differentiating the dynamic from quasi-static deformation).…”