A method of producing a thermoplastic composite article comprising a porous core layer (310, 410, 510, 610, 710, 810, 910, 1010) comprising a plurality of reinforcing glass fibers, a thermoplastic polyolefin material and expandable graphite material, wherein the thermoplastic composite article further comprises a skin (270, 320, 420, 520, 620, 720, 820, 940) coupled to a first surface of the porous core layer (310, 410, 510, 610, 710, 810, 910, 1010), wherein the porous core layer comprises the reinforcing glass fibers from 30 to 60 weight percent and the expandable graphite material from 5 to 15 weight percent with the balance of the porous core layer comprising the thermoplastic polyolefin material, the method comprising: combining the thermoplastic polyolefin material, the reinforcing glass fibers, and the expandable graphite material in a mixture to form an agitated aqueous foam; disposing the agitated aqueous foam onto a wire support; evacuating the water to form a web; heating the web comprising the reinforcing glass fibers, the thermoplastic polyolefin material and the expandable graphite material to a first temperature above a melting point of the thermoplastic polyolefin material without any substantial lofting of the expandable graphite material; compressing the heated web to a first thickness of no more than 4 mm to provide a porous core layer (310, 410, 510, 610, 710, 810, 910, 1010), wherein the porous core layer (310, 410, 510, 610, 710, 810, 910, 1010) comprises open cell structures formed from the reinforcing glass fibers and the thermoplastic polyolefin material after compression of the heated web, and wherein the expandable graphite material is present in the formed open cell structures of the porous core layer (310, 410, 510, 610, 710, 810, 910, 1010) in a substantially uniform distribution from the first surface to a second surface of the porous core layer (310, 410, 510, 610, 710, 810, 910, 1010); and coupling the skin (270, 320, 420, 520, 620, 720, 820, 940) to the first surface of the porous core layer (310, 410, 510, 610, 710, 810, 910, 1010) either before compressing of the heated web or after compressing of the heated web to provide the thermoplastic composite article, wherein the skin (270, 320, 420, 520, 620, 720, 820, 940) comprises a scrim or a film, wherein the thermoplastic composite article provides a sound absorption coefficient in an as-produced state of the provided thermoplastic composite article of at least 0.2 at 2400 Hz as tested by ASTM E1050 dated 2010 when the porous core layer (270, 320, 420, 520, 620, 720, 820, 940) is no more than 4 mm thick. combining the thermoplastic polyolefin material, the reinforcing glass fibers, and the expandable graphite material in a mixture to form an agitated aqueous foam; disposing the agitated aqueous foam onto a wire support; evacuating the water to form a web; heating the web comprising the reinforcing glass fibers, the thermoplastic polyolefin material and the expandable graphite material to a first temperature above a melting point of the thermoplastic polyolefin material without any substantial lofting of the expandable graphite material; compressing the heated web to a first thickness of no more than 4 mm to provide a porous core layer (310, 410, 510, 610, 710, 810, 910, 1010), wherein the porous core layer (310, 410, 510, 610, 710, 810, 910, 1010) comprises open cell structures formed from the reinforcing glass fibers and the thermoplastic polyolefin material after compression of the heated web, and wherein the expandable graphite material is present in the formed open cell structures of the porous core layer (310, 410, 510, 610, 710, 810, 910, 1010) in a substantially uniform distribution from the first surface to a second surface of the porous core layer (310, 410, 510, 610, 710, 810, 910, 1010); and coupling the skin (270, 320, 420, 520, 620, 720, 820, 940) to the first surface of the porous core layer (310, 410, 510, 610, 710, 810, 910, 1010) either before compressing of the heated web or after compressing of the heated web to provide the thermoplastic composite article, wherein the skin (270, 320, 420, 520, 620, 720, 820, 940) comprises a scrim or a film, wherein the thermoplastic composite article provides a sound absorption coefficient in an as-produced state of the provided thermoplastic composite article of at least 0.2 at 2400 Hz as tested by ASTM E1050 dated 2010 when the porous core layer (270, 320, 420, 520, 620, 720, 820, 940) is no more than 4 mm thick.