A composite panel structure of a polymer matrix core sandwiched by metal layers is described. The polymer matrix comprises 1-30 wt % fluoropolymer and 70-99 wt % of a flame retardant mineral. The fluoropolymer may be polyvinylidene fluoride (PVDF) with a high limiting oxygen index, which confers fire resistance properties to the polymer matrix and the composite panel structure. The composite panel structure may be used on the exterior of buildings and may fulfill building code requirements for the polymer matrix core being noncombustible as determined by ASTM E136 and CAN/ULC S114 compliance.