Fire behaviour of a Carbon/Nomex honeycomb sandwich composite used in aircraft interior

Fire behaviour of a carbon/Nomex honeycomb composite, used as ceiling panel in aircraft interiors, was investigated in Cone Calorimeter at different incident heat fluxes, ranging from 20 to 70 kW/m2. The material exhibited good fire performance with relatively low amount of heat release and long ignition times. Combustion of the material at 40 kW/m2 proceeded in one stage, while at higher heat fluxes two stages were observed. The burning mechanisms and char formation during thermal decomposition at different heat fluxes was also examined. The long tail after flame-out in heat release curves and the significant increase of CO production and mass loss were analysed with respect to char residue.

Analysis of friction and cutting parameters when milling honeycomb composite structures

In machining, tool/workpiece interface parameters are complicated to estimate by experimental means alone. Numerical methods can then give critical solutions to predict and analyze the parameters influencing the machining. The friction between the tool and the cutter has a direct influence on the milling parameters. Therefore, it is necessary to understand the friction mechanism between the tool and the workpiece to estimate the milling parameters of Nomex honeycomb structures correctly. This work aims to present a 3D Finite Element numerical model allowing the prediction of the cutting forces correctly, the morphology of the chips, and the surface quality generated during the milling of this type of structure. These studies were obtained using the commercial software ABAQUS/Explicit. It has been demonstrated that the coupling between the isotropic elastoplastic approach and the Coulomb friction law can easily simulate the milling of Nomex honeycomb structures and gives excellent results in comparison with those obtained experimentally.

Experimental and theoretical research on four-point bending performance of Nomex honeycomb sandwich panels

In order to reveal the relationship between the four-point bending behaviour and structural parameters of Nomex honeycomb sandwich panels (NHSP), a comparison of the bending performance of sandwich panels with different specifications and directions was conducted. The ability of NHSP to improve the strength and stiffness of bare honeycombs and aluminium plates was also quantified. Furthermore, based on experimental data and existing theories, the critical relationship of each failure type of NHSP under four-point loading conditions was derived. The drawn bending failure map reveals the relationship between core layer performance parameters and failure types, which can provide guidance for the optimal design of sandwich structure in practical application.

In-plane compression modulus and strength of Nomex honeycomb cores

The stress-strain response and deformation mechanism of a range of Nomex honeycomb cores tested under in-plane compression has been examined experimentally. The cores with a thin wall displayed extensive bending deformation of the cell walls inclined to the horizontal (loading is vertical) and failed in bending. The cores with thicker walls failed by a shear-type instability of the cells indicated by tilting of vertical cell wall segments. The failure strain decreased with increasing core density. The modulus and compressive strength of the core were compared to micromechanical predictions. Normalized modulus and strength values varied between the various cores. The average modulus and strength results allow backing out of the modulus and bending strength of the Nomex paper. The results were in reasonable agreement with published tensile test results and composite micromechanics.

Effect of extreme cold temperatures on quasi-static indentation and impact behavior of woven carbon fiber epoxy composite sandwich panels with nomex honeycomb core

The effect of extreme cold temperatures on the quasi-static indentation and the low velocity impact behavior of woven carbon/epoxy composite sandwich panels with Nomex honeycomb core was investigated. Impact tests were performed at room temperature, –70°C, and –150°C. Two sizes of hemispherical impactor were used combined to three different impactor masses. All the impact tests were performed at the same initial impact velocity. The effect of temperature on the impact behavior is investigated by studying the load history, load-displacement curves and transmitted energy as a function of time curves. Impact damage induced at various temperatures was studied using different non-destructive and destructive techniques. Globally, more damages are induced with impact temperature decreasing. The results also show that the effect of temperature on the impact behavior is function of the impactor size.