A load bearing panel member having a first portion, a second portion, and an appearance surface portion is formed by injection molding such that the first portion includes a plurality of rib members forming a grid pattern on the first portion and another plurality of rib members extending toward the periphery of the first portion which may be non-orthogonal to each other and to the rib members forming the grid pattern. A tubular cavity may be formed within each of the non-orthogonal rib members by injecting a gas into the rib member during the molding process forming the panel. An appearance surface portion attached to the first portion and second portion of the panel member forms an integral hinge between the first and second portions of the panel member. The panel member may be configured as a floor panel of a vehicle.