Experimental and computational studies on the thermal behavior and fire retardant properties of composite metal foams

Abstract

a b s t r a c tA comprehensive experimental and computational evaluation of thermal behavior and fire retardant properties of composite metal foams (CMFs) is reported in this study. Thermal behavior characterizations were carried out through specific heat, effective thermal conductivity, and coefficient of thermal expansion analyses using differential scanning calorimetry, high temperature guarded-comparativelongitudinal heat flow technique, and thermomechanical analyzer (TMA), respectively. The experimental results were compared with analytical results obtained from, respectively, rule of mixture, Brailsford and Major's model, and modified Turner's model for verification. United States Nuclear Regulatory Commission (USNRC) standards were employed as regulatory standards and criteria for fire retardant property study. The results revealed a superior thermal resistance and fire survivability of CMFs compared to 304L stainless steel. A physics-based three-dimensional model accounting for heat conduction was built using Finite Element Analysis to validate the reliability of the experimental results. The model led to a good reproduction of the experimentally measured data when comparing CMF to bulk stainless steel. This research indicates that one of the potential applications of lightweight CMFs can be in nuclear spent fuel casks replacing conventional structural and radiation shielding materials with demonstrated benefits of excellent thermal isolation, fire retardant, light weight and energy absorption capabilities.

Overview of Composite Metal Foams and Their Properties and Performance

“…The porosities accommodate local thermal expansion, which reduces the amount of strain experienced by the material, as a whole. The experimental results of specific heat, thermal conductivity, and CTE were all verified using analytical models and ensured the reliability of the findings …”

“…Knowing that the sphere wall to outer sphere diameter stays relatively constant, the material percentage can be calculated first by relating the densities. These calculations show approximately 16% volume is sphere wall, 26% matrix, and 58% air …”

“…Metal foams have been known to make efficient and effective heat sinks due to their large surface area resulting from the presence of porosities . The thermal characterization of CMFs includes their specific heat, effective thermal conductivity (ETC), and coefficient of thermal expansion (CTE) . The results of this study can be found in Table .…”

“…The measured specific heat of both Al–S and S–S CMF has a lower value than bulk aluminum at room temperature due to the existence of the stainless steel spheres in the material. This type of measurement was done using shavings of the matrix and sphere material, not taking into account the effect of the sphere spacing and CMF specific geometry, which aids in its thermal properties …”

“…The thermal conductivity of CMF showed much lower values for both Al–S and S–S CMF than their bulk counterparts due to the air trapped inside the material, acting as an efficient thermal insulator. In addition to a reduction in thermal conductivity, the property remains stable between multiple sphere sizes as long as the sphere wall to diameter ratio remains constant . In addition, the S–S CMF samples have little variation in their thermal conductivity across a broad temperature range, making it a practical material for application and reliable under accident conditions.…”