The application of burning dummy test system in the field of flame retardant clothing

Combustion dummy test system in the test fire and thermal radiation conditions, to ensure the safety of staff important test methods, for a long time, China mainly uses the textile vertical combustion test method and limited oxygen index method test to evaluate the flame retardant protective performance of clothing. These two methods can only explain whether the clothing fabric is flame retardant, can not explain the resistance of clothing to flame or electric arc generated by high temperature, high heat. Burning dummy test system uses a dummy in a simulated test environment to test the survival of a variety of harsh conditions limit value.

A. Combustion dummy test system composition and design principles
The system mainly consists of a combustion dummy, data acquisition device, flame generation and control device, skin heat transfer model and burn assessment model, as well as the system centralized control and application software platform. The design principle is to simulate the thermal exposure process of the dressed human body in the combustion flame, test the change in the surface temperature of the dummy, and predict the percentage of second and third degree burns and total burn area that may be caused to the skin, the larger the percentage of burn area, the worse the flame retardant protection performance of the garment, and the testing principle of the system.

Second, burning dummy test system burning dummy research

Retrieve relevant information at home and abroad, the use of non-metallic materials to make burning dummy body, clothing test flame duration is generally 4 s, the dummy surface may need to withstand up to 300 ℃ burning flame, therefore, the dummy body material must have good thermal stability under the short burning flame of more than 300 ℃, can withstand the harsh fire environment; dummy surface laid sensor response to the burning flame, should be close to the human skin response to the burning flame; data acquisition and processing device can quickly collect the dummy surface sensor data.

1、Dummy body
According to the above design requirements, by comparing and analyzing the physical properties of high temperature resistant materials, the polyimide with the highest temperature resistance level, the best mechanical properties, dielectric properties and corrosion resistance is selected as the main material of the combustion dummy body, and according to the appearance characteristics of the dummy model, the dummy body model is manufactured according to the following process: synthetic polyimide → curing resin material → making molds for each anatomical segment of the human body and high temperature molding → vacuum curing → surface treatment.

2、Dummy surface heat sensor
The role of the dummy skin surface heat sensor is to sense the degree of heat exposure to the human skin in the fire environment, so as to predict the degree of skin burns that may occur. Foreign thermal sensors used mainly TPP copper heat flow meter sensor, adiabatic copper sensor and embedded thermocouple sensor. Among these 3 sensors, the adiabatic copper sheet sensor is the most reliable thermal sensor. Experiments show that the adiabatic copper sheet sensor is similar to the TPP copper sheet heat flow meter sensor, with stable readings, rapid response, wide range and good repeatability, while the sensor size is smaller than the TPP sensor, occupying much less space and mass than the TPP copper sheet heat flow meter. The average response speed of the embedded thermocouple sensor is slower than that of the adiabatic copper sheet sensor under high thermal environment. For this reason, the group developed an adiabatic copper sheet sensor with a diameter of 1 cm and a thickness of 0.16 cm. Using a brazing process, the copper sheet was connected to a K-type thermocouple with a wire diameter of 0.2 mm, and a measurement accuracy of 0.2 °C was achieved.

3、Sensor layout
Considering the dummy area, data acquisition, and burn evaluation calculation, 120 adiabatic copper sensors were evenly distributed on the dummy surface. When installing the sensors, holes were drilled with a milling cutter according to the diameter and depth of the copper sheet to ensure a close fit between the sensor surface and the dummy body, and a uniform distribution of sensors.