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Validation of Heat Transfer Thermal Decomposition and Container Pressurization of Polyurethane Foam

Scott, Sarah N.; Dodd, Amanda B.; Larsen, Marvin E.; Suo-Anttila, Jill M.; Erickson, Kenneth L.

Polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. In fire environments, gas pressure from thermal decomposition of polymers can cause mechanical failure of sealed systems. In this work, a detailed uncertainty quantification study of PMDI-based polyurethane foam is presented to assess the validity of the computational model. Both experimental measurement uncertainty and model prediction uncertainty are examined and compared. Both the mean value method and Latin hypercube sampling approach are used to propagate the uncertainty through the model. In addition to comparing computational and experimental results, the importance of each input parameter on the simulation result is also investigated. These results show that further development in the physics model of the foam and appropriate associated material testing are necessary to improve model accuracy.

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TYPE SAND Report YEAR 2014
DOIOSTI

Modeling and Validation of the Thermal Response of TDI Encapsulating Foam as a function of Initial Density

Dodd, Amanda B.; Larsen, Marvin E.

TDI foams of nominal density from 10 to 45 pound per cubic foot were decomposed within a heated stainless steel container. The pressure in the container and temperatures measured by thermocouples were recorded with each test proceeding to an allowed maximum pressure before venting. Two replicate tests for each of four densities and two orientations in gravity produced very consistent pressure histories. Some thermal responses demonstrate random sudden temperature increases due to decomposition product movement. The pressurization of the container due to the generation of gaseous products is more rapid for denser foams. When heating in the inverted orientation, where gravity is in the opposite direction of the applied heat flux, the liquefied decomposition products move towards the heated plate and the pressure rises more rapidly than in the upright configuration. This effect is present at all the densities tested but becomes more pronounced as density of the foam is decreased. A thermochemical material model implemented in a transient conduction model solved with the finite element method was compared to the test data. The expected uncertainty of the model was estimated using the mean value method and importance factors for the uncertain parameters were estimated. The model that was assessed does not consider the effect of liquefaction or movement of gases. The result of the comparison is that the model uncertainty estimates do not account for the variation in orientation (no gravitational affects are in the model) and therefore the pressure predictions are not distinguishable due to orientation. Temperature predictions were generally in good agreement with the experimental data. Predictions for response locations on the outside of the can benefit from reliable estimates associated with conduction in the metal. For the lighter foams, temperatures measured on the embedded component fall well with the estimated uncertainty intervals indicating the energy transport rate through the decomposed region appears to be accurately estimated. The denser foam tests were terminated at maximum allowed pressure earlier resulting in only small responses at the component. For all densities the following statements are valid: The temperature response of the embedded component in the container depends on the effective conductivity of the foam which attempts to model energy transport through the decomposed foam and on the stainless steel specific heat. The pressure response depends on the activation energy of the reactions and the density of the foam and the foam specific heat and effective conductivity. The temperature responses of other container locations depend heavily on the boundary conditions and the stainless steel conductivity and specific heat.

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TYPE SAND Report YEAR 2014
DOIOSTIDOIOSTI

Intermediate-scale fire performance of composite panels under varying loads

Fire and Materials 2013 - 13th International Conference and Exhibition, Conference Proceedings

Brown, Alexander B.; Dodd, Amanda B.

New aircraft are being designed with increasing quantities of composite materials used in their construction. Different from the more traditional metals, composites have a higher propensity to burn. This presents a challenge to transportation safety analyses, as the aircraft structure now represents an additional fuel source involved in the fire scenario. Most of the historical fire testing of composite materials is aimed at studying decomposition, flammability or yield strength under fire conditions. The majority of this testing has been performed on a small-scale. Heterogeneous reactions are often length-scale dependent, and this is thought to be particularly true for composites which exhibit significant microscopic dynamics that can affect macro-scale behavior. A series of discovery tests has been designed to evaluate composite materials under various structural loading conditions with a consistent applied thermal boundary condition. Mass-loss, heat flux, and temperature response have been measured throughout the experiment. Several panels have been tested, including simple composite panels, and sandwich panels. A major objective of the testing was to understand the importance of the structural loading on a composite material during exposure to firelike conditions. During flaming combustion at early times, there are features of the panel decomposition that are unique to the type of structural loading imposed on the panels. At load levels tested, fiber reaction rates at later times appear to be independent of the structural loading.

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TYPE Conference YEAR 2013
OSTIScopus

The behavior of carbon fiber-epoxy based aircraft composite materials in unmitigated fires

Western States Section of the Combustion Institute Spring Technical Meeting 2012

Brown, Alexander L.; Dodd, Amanda B.; Erickson, Kenneth L.

New aircraft are being designed with increasing quantities of composite materials used in their construction. Different from the more traditional metals, composites have a higher propensity to burn. This presents a challenge to transportation safety analyses, as the aircraft structure now represents an additional fuel source involved in the fire scenario. Performance testing data for composites burning in a fire at the integral scales of an accident event are nearly non-existent. This report describes fire tests for relevant carbon fiber epoxy materials that were designed to explore the bulk decomposition behavior of said material in a severe fire. Together with TGA decomposition data, the material is found to decompose in three mostly distinctive and sequential phases, epoxy pyrolysis, char oxidation, and carbon fiber oxidation. Fires were not severe in their thermal intensity compared to liquid fuel fires. Peak thermal intensities of around 220 kW/m2 or 1100 °C are achieved at very low air flow rates. The burn tests were remarkable in their duration, lasting 4-8 hours for 25-40 kg of combustible material.

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TYPE Conference YEAR 2012
ScopusOSTI
Results 26–50 of 66
Results 26–50 of 66