3D numerical modeling and experimental validation of machining Nomex® honeycomb materials

Abstract

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Study on the Cutting Damage Mechanism of Aramid Honeycomb Based on the Progressive Damage Model

“…As for contact conditions between the cutting tool and the specimen, 'Hard contact' enforced with a Lagrange multiplier representing the contact pressure in a mixed formulation was used to model the normal behavior, and Coulomb friction implemented with the penalty contact algorithm (relative motion in the absence of slip is equal to the friction force divided by the penalty stiffness) was established to model the tangential behavior. Due to discontinuous distribution and small thickness of the honeycomb walls, the contact area between the wall and the cutting tool is minimized so that a low friction coefficient between 0.1~0.25 [14,19,20] is fine for simulation.…”

“…Core material of the honeycomb has obvious anisotropic and heterogeneous characteristics. Considering the independence of fracture modes of the matrix and the core material, transversely isotropic stress-strain relationship based on the classical laminate theory and Hashin-type progressive damage model were used in the finite element model [14,22]. During the cutting procedure, disc cutting tool contacts the cell wall of the honeycomb, whose aramid fibers will be broken mainly under bending forces and resin will be crushed mainly under out-of-plane compressive forces on mesoscale.…”

“…The detailed model considers the multi-layer nature of the honeycomb material, which models the aramid paper and phenolic resin individually. Four modelling approaches of Nomex honeycomb were benchmarked in literature [13], including single-layer isotropic approach (isotropic homogenized model), single-layer orthotropic approach (orthotropic homogenized model), multi-layer resin coating approach (detailed model based on planar laminate theory), and multi-layer resin corner approach (detailed model considering resin accumulation in the hexagon corners); the single-layer orthotropic approach (orthotropic homogenized model) enabled simultaneous calibration for all four loading conditions and had a good agreement with the test results, while a detailed model respecting the real geometry of the cells can give more information [14]. In addition, an analytical homogenized model of composite cell wall honeycomb was also developed by Wang et al [15] for computing costs reducing by modelling the locally heterogeneous honeycomb as a homogeneous orthotropic bulk, whose stiffness matrix was derived by combining Gibson and Ashby's model [16] and the classic laminated beam theory model.…”

“…Jaafar et al [17] reported an orthotropic finite element modelling method of the Nomex honeycomb cutting based on the 2D Hashin criteria, which predicts the cutting forces and surface quality compared with the experimental results. Furthermore, the model based on the 2D Hashin criteria was compared with that based on the Tsai-Wu criteria, and it was found that the 2D Hashin criteria will underestimate the cutting forces [14], which indicates that the out-of-plane delamination should not be neglected. Liu et al [18] used mesoscopic shell model based on the 2D Hashin criteria, which includes fiber tensile fracture, fiber compressive fracture, matrix tensile failure, and matrix compressive failure to characterize the tearing defects of the Nomex honeycomb wall during cutting, and it was reported that the deformation of honeycomb wall and the cutting force in direction parallel to honeycomb wall have a major impact on the formation of tearing defects.…”

Flatwise compression behaviour and mechanical properties of gradient-tandem nomex honeycomb sandwich panels

“…[25][26][27][28] The modelling approaches for honeycomb structures are based on nonlinear springs, 9,29 solid elements, 30 and shell elements. 20,[31][32][33] The shell element models are divided into single-layer and multi-layer models. The single-layer isotropic model can reasonably simulate the buckling and failure of a Nomex honeycomb under compression loading and is suitable for studying the bearing capacity of Nomex honeycomb structures.…”