| When confronted with various complex heat-flux environments,firefighters always rush to carry out fire rescues.But high-intensity rescue work can cause heat stress in firefighters and may even cause cardiovascular and neurological diseases.Thus,firefighter protective clothing with good performance is particularly important.At present,the optimization research on the performance of various layers of firefighter protective clothing and the in-depth study on the influencing factors of the thermal protection performance are gradually improved.However,the problem of overprotection of firefighter protective clothing and heaviness as well as sultriness has not been solved.The honeycomb sandwich structure has excellent thermal insulation and stability performance,and it can be applied to the thermal liner of firefighter protective clothing,which is helpful for resolving the contradiction between thermal protection and thermal comfort of firefighter protective clothing,but its thermal protection performance of honeycomb porous structure can be further optimized.In view of the above problems,this thesis is based on the heat transfer mechanism of thermal protective fabric and honeycomb sandwich structure,optimizes the porous structure of honeycomb sandwich structure of firefighter protective clothing,and further investigates the influence of the fabrics of flame-retardant outer liner and the core thickness as well as the porous structure of the thermal liner of firefighter protective clothing on its thermal protection performance,explore the effect of the optimized honeycomb porous structure on the thermal protection performance,and obtain the optimal honeycomb sandwich structure to meet the needs of the fire protection field.The main research findings and conclusions of this thesis are as follows:(1)The thermal protective fabric system is mainly coupled heat transfer of heat radiation and heat conduction.The heat transfer between the thermal protective fabric combination and the human body is divided into coupled heat transfer of heat convection,thermal radiation and heat conduction,and coupled heat transfer of heat radiation and heat conduction according to the thickness of the air layer.The heat transfer in the honeycomb sandwich structure is mainly the coupling of heat radiation and heat conduction,and the effective thermal conductivity increases as the wall thickness of the honeycomb decreases.(2)Based on the honeycomb I-shaped porous structure of the honeycomb sandwich structure,the porous structure of the honeycomb sandwich structure is optimized.Such three kinds of core thickness of 2.0mm,2.5mm,2.9mm are designed.Four improved and optimized honeycomb porous structures,honeycomb A-shaped porous structure,honeycomb O-shaped porous structure,honeycomb L-shaped porous structure and honeycomb V-shaped porous structure,are designed.Based on laser cutting technology,the manufacturing processes of honeycomb sandwich structure thermal protective fabrics including positioning,focusing,debugging cutting power and speed,importing data and cutting are mastered.More than 280 pieces of honeycomb sandwich structure thermal liner samples were cut and prepared.(3)According to two kinds of outer shell fabrics,three sorts of honeycomb core thicknesses,four kinds of honeycomb porous structures and a solid control group,a total of 30 sets of flash thermal protection performance test protocol were designed.The principle and instrument structure of the flash fire protection performance test experiment were studied,and the experimental process was mastered.More than 90 experiments were carried out on 30 sets of test protocol.(4)The experimental results show that: 1.Nomex? IIIA outer shell has better thermal protection performance than PBI matrix outer shell,but its thermal stability is not as good as PBI matrix outer shell;2.When outer shell fabrics and honeycomb porous structure of the thermal liner are the same,in the range of the core thickness designed in this thesis,the thermal protection performance of the honeycomb sandwich structure fabrics of firefighter protective clothing increases as the core thickness increases,and there is a linear correlation between them;3.For various honeycomb porous structured fabrics of firefighter protective clothing,the honeycomb Ashaped porous structure has the best thermal protection performance,and the V-shaped porous structure has the worst thermal protection performance.The thermal protection performance of the I-shaped porous structure,O-shaped porous structure and L-shaped porous structure is between the A-shaped and V-shaped porous structure.Compared with the I-shaped porous structure,A-shaped porous structure and L-shaped porous structure have a significant effect on improving the thermal protection performance of firefighting honeycomb sandwich fabrics;4.When the flame-retardant outer shell is PBI matrix and Nomex? IIIA,the combination of 2.9mm core thickness and honeycomb A-shaped porous structure is the optimal combination,whose thermal protection performance of the firefighter protective clothing is the best. |
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