US Patent 7337544 Method of forming a composite door structure

A method of forming a composite door is disclosed. The method comprises: mixing together a thermoplastic polymer with an organic fibrous material in a ratio such that the organic fibrous material constitutes 40 to 60 percent by weight of the mixture; extruding the mixture under heat and pressure to create a thin sheet form; cutting the sheet to a predetermined size; removing material from at least one surface of the sheet to create a homogeneous appearance devoid of obvious fibrous particles; thermoforming the sheet to impart to the at least one surface an exterior three dimensional door surface to create a thin door facing; and assembling two of the thermoformed thin door facings, a peripheral frame and a core material into a door.