An interior trim panel, such as a headliner, formed by a substrate composed of a fibrous or porous batt material, such as polyethylene terephthalate (PET). The substrate includes a first, back side and second, front side. In order to increase the strength of the substrate, dimples or impressions are formed in the back side of the substrate and corresponding projections are formed extending from the opposite front side by simultaneously compressing both sides of the fibrous batt material. A structural layer of material is then attached to the substrate, preferably to the projections of the substrate, resulting in an 'I-beam' structure that further enhances the strength of the interior trim panel. In another embodiment, a second layer of fibrous or porous batt material may be placed between the projections before fixedly attaching the structural layer of material to the substrate.