A composite panel exhibiting high flexural strength while reducing mass as compared with conventional composite panels is provided. The improved panel includes a rigid frame having outer edges defining a perimeter of the panel and inner edges defining a perimeter of a structural filler chamber, wherein the frame has a thickness at its outer edges that is narrower than at its inner edges; first and second sheet-like material layers bonded to opposite sides of the rigid frame to define, together with the inner edges of the rigid frame, a volume of the structural filler chamber; and a structural filler disposed in the chamber to provide compressive strength between the sheet-like material layers.