Ph.d.-forsvar ved Anna Sandinge

Anna Sandinge forsvarer sin ph.d.-afhandling "The effect of ageing on fire safety of composite materials"

Forsvaret finder sted på DTU tirsdag den 2. marts 2021 klokken 13:00.

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Kort resumé: 

New materials and products are introduced to the market every day. They are evaluated regarding function, material properties and fire performance. Regarding the fire behavior, the materials must fulfil international fire requirements and achieve a fire classification before introduced to the market. The fire behavior is tested on newly produced materials, as stated by the fire classification regulations. However, with time, materials and products age and as a result the material properties changes. Studies show that mechanical properties, such as strength, are deteriorated when the material gets older. The studied effects of aged materials fire performance are limited, especially when dealing with composite materials.

Composite materials, consisting of a polymer resin and fibers, are lightweight and show good mechanical properties. The usage of these materials is increasing within areas such as construction products, marine applications, products and materials used on railway vehicles and in automotive.  However, as they are combustible, they will burn, and the fire safety of the application is threatened. To have knowledge of the combination of increased usage of these materials, their fire behavior and the effect from ageing is important in order to maintain safety.

The objective of the PhD study was to evaluate the effect of accelerated ageing on the reaction-to-fire properties, i.e. the fire behavior during the development phase of a fire, of selected composite materials and sandwich products with intumescent coating which expands during the fire to protect the material behind. The materials were aged using two accelerated ageing methods: thermal ageing with a temperature of 90 °C and moisture ageing with a moderately increased temperature of 40 °C and a relative humidity in the atmosphere of 90 %. Samples were collected from the ageing chambers after one week, two weeks and four weeks of ageing. The reaction-to-fire properties were evaluated with the Cone Calorimeter test and the Smoke chamber test with FTIR (Fourier Transform Infrared) gas analysis. From the Cone Calorimeter tests, parameters such as time to ignition, heat release rate (size of the fire) and smoke production were evaluated. The smoke chamber evaluated the smoke production in relation to the smoke density, i.e. the visibility through the smoke, as well as the toxicity of the smoke. In order to have a material with good fire behavior, preferred fire properties are as follows, a long time to ignition, a low heat release rate, low smoke production and a low content of the toxic gas species.

The results from the ageing study and the fire testing showed that the fire behavior of the selected composite materials and sandwich panels with intumescent coating were affected by accelerated ageing, both by the thermal exposure and by the moisture exposure. The effect was not consistent as the results showed both an improved and deteriorated fire behavior. The materials reacted different to the accelerated ageing exposure. Generally, the time to ignition was both shorter and longer after ageing. The heat release rate was in most cases higher for the aged samples than the unaged and the smoke production was both higher and lower. From the FTIR analysis of the smoke produced in the smoke chamber tests, it was seen that the accelerated ageing changed the gas specie content in the smoke, with both increased and decreased amount.

However, further research dealing with the topic, the effect of accelerated ageing on fire behavior is needed. This study was conducted with three selected composite laminates and three sandwich products with intumescent coating. The results were not consequent and further research and data is required to give a deeper knowledge of the ageing mechanism and the effect from ageing.

Tidspunkt

tir 02 mar 21
13:00 - 16:00

Hvor

Link til forsvaret: https://dtudk.zoom.us/j/63793804813