An analytical and experimental investigation of the decomposition of glass -filled polymer composites
An analytical and experimental investigation has been performed to determine the thermal behavior of two glass-filled, decomposing polymer composites. A one-dimensional, transient numerical model has been developed to predict the overall thermally-induced response of these materials, without including the idealized assumption of local-thermal equilibrium. For both materials, the expansion characteristics and volumetric heat transfer coefficients were experimentally determined for input into the numerical model.^ The results of the numerical study with a prescribed surface heat flux of 279.7 kW/m$\sp2$ indicate that local-thermal equilibrium does not exist in either H41N or MXBE-350. In fact, solid to gas temperature differences of 500$\sp\circ$C exist locally for MXBE-350. While for the tighter, more fibrous H41N differences as high as 200$\sp\circ$C are predicted locally for the times investigated. For H41N, pressures in excess of 10 atmospheres were predicted, and the existence of such high pressures has been verified experimentally.^ An investigation into the effects of the idealized assumption of local-thermal equilibrium revealed significant errors associated with the assumption for both materials. Solid temperature differences between the actual and idealized cases were as high as 100$\sp\circ$C and 180$\sp\circ$C locally for H41N and MXBE-350, respectively. As a result, measurable errors are evident in the mass loss and pressure profiles for the idealized case. The errors in the pressure and mass loss profiles are significant because spallation and/or cracking are highly dependent on stress concentration and material strength, which are linked to internal pressure and stage of decomposition, respectively. From the results of this study, it is evident that accurate numerical modeling can only be achieved when the idealized assumption of local-thermal equilibrium is not incorporated into the modeling scheme. ^
Engineering, Mechanical|Engineering, Materials Science
"An analytical and experimental investigation of the decomposition of glass -filled polymer composites"
Dissertations and Master's Theses (Campus Access).