FEATURES THE TESTING OF AVIATION MATERIALS ON FIRE SAFETY. Part 3. Test on smoke density. Influence of sample thickness on registered characteristics

According to requirements of aviation normative documents, materials of internal furnish of passenger cabins have to be checked on smoke-generating ability. State Standard 24632 is applied in Russia at smoke density qualification tests of aviation materials. Unlike the method described in item 4.18 of Interstate Standard 12.1.044, smoke density defined according at State Standard 24632 belongs to area of the material, instead of to its weight. Therefore, when using polymeric materials of aviation assignment of different thickness, there is need of carrying out tests of samples for each option of thickness. According to requirements of aviation norms on which the admissibility of application of materials in products is defined by the main characteristics of smoke density are kinetic indicators, that is the optical density for the given period of time (90, 120 or 240 sec). In this work foreign experience is analyzed, researches are conducted and available data on influence of thickness for different types of monolithic composite materials on registered indicators of smoke density are generalized. A presence of extremum (maximum) on schedules of change of characteristics of smoke density from thickness of sample of material is shown. Depending on type of material and the characteristic time of smoke density, thickness at which the maximum of smoke density is observed may change in the range from 1 to 3 mm. The equations of kinetic characteristics of smoke density describing character depending on thickness of tested sample are offered. Calculations of factors of the equations are carried out for the material VPS-41, the regression analysis is made, adequacy of the used mathematical models to experimental data is checked and confirmed and high level of correlation is established.