Numerical Analysis and Design of Carbon-Foam-based Garment and Helmet for Firefighters

Carbon foam is known for its excellent insulation properties and is also regarded as an effective shock absorbing material. In the present work, a numerical parametric study has been performed to investigate and predict the merits of using carbon foam as an alternative material for firefighter garment and helmet. We considered open-cell non graphitic carbon foam because of its high porosity, better mechanical strength, and lower thermal conductivity. It absorbs impact-shocks efficiently and also provides adequate thermal insulation.In the present study, numerical simulations of flame test and impact test as designed by the National Fire Protection Association (NFPA) are performed on firefighter garment and helmet. In reference to the work done by Elgafy and Mishra [1], for the flame test on the garment, carbon foams with different thermal conductivity, porosity, and density are introduced to conduct a parametric study. Additionally, the thickness of the introduced carbon foam fabrics is varied to acquire optimum design [1]. Simulation is conducted for a square planar 2D geometry of the clothing consisting of different fabric layer and a transient double-precision pressure-based implicit solver is used. The new anticipated thermal protection system is tested under the harsh thermal environmental conditions to which firefighters are generally exposed. The parametric study [1] shows that employing carbon foam fabric with one set of designed parameters leads to weight reduction of 33% and 56% in the outer shell and the thermal liner respectively and a temperature reduction of 2% at the inner edge of the garment as compared to the traditional firefighter garment model used by Song et al. [2]. Carbon foam fabric with another set of designed parameters results in a weight reduction of 25% and 28% in the outer shell and thermal liner respectively and a temperature reduction of 6% at the inner edge of the garment [1]. Thus, carbon foam fabrics are seen to make the firefighter's garment thermally more protective and lighter in weight [1].Next, impact test simulation is conducted for a 3D hemispherical helmet model firmly seated on an aluminum headform. Parameters, such as porosity and density of carbon foam and thickness of the helmet, are varied to check their effects on the overall performance of the carbon-foam helmet. Crushable foam model of abaqus CAE software is used to define the carbon foams, and a dynamic explicit solver is used for the computation. The results of the simulation exhibit adequate impact resistance for the carbon-foam helmet. In addition, net helmet weight reduction of 56-61 % was achieved as compared to the currently used modern firefighter helmet. Finally, a flame test was conducted over the carbon-foam helmet thickness using a method similar to that used for the firefighter garment. Temperature is observed to drop along the thickness of the carbon-foam helmet, and reaches near-ambient temperature at the inner edge of the helmet.