AbstractThis study is based on the use of integral, hybrid thermal barrier to protect the core of the composite structure. Thermal barrier treatments evaluated in this study include ceramic fabric, ceramic coating, intumescent coating, hybrid of ceramic and intumescent coating, silicone foam, and phenolic skin. The composite systems evaluated in combination with thermal barrier treatments included glass/vinyl ester, graphite/epoxy, graphite/bismaleimide, and graphite/phenolic. All configurations were tested for flammability characteristics. These included smoke density and combustion gas generation (ASTM E‐662), residual flexural strength (ASTM D‐790), heat release rate, and ignitability (ASTM E‐1354). ASTM E‐662 test method covers the determination of specific optical density of smoke generated by solid materials. ASTM D‐790 test method covers the determination of flexural properties of composite materials in the form of rectangular bars. ASTM E‐1354 (cone calorimeter) covers the measurement of the response of materials exposed to controlled levels of radiant heating with or without an external ignitor, and is used to determine the ignitability, heat release rates, mass loss rates, effective heat of combustion, and visible smoke development. Without any fire barrier treatments, all composite systems evaluated in this study failed to meet ignitability and peak heat release requirements of MIL‐STD‐2031 (SH) at radiant heat fluxes of 75 and 100 kW m−2, respectively. Intumescent coating and a hybrid system consisting of intumescent coating over ceramic coating were the most effective fire barrier treatments for composite systems evaluated in this study. Using either of these treatments, all composite systems met the ignitability requirements of 90 and 60 at 75 and 100 kW m−2, respectively. Except for glass/vinyl ester, all systems also met the peak and average heat release requirements of MIL‐STD‐2031 (SH) at radiant heat fluxes of 25, 75, and 1
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