Process for making 7xxx series aluminum/fiber reinforced polypropylene hybrid part for automotive crash absorption application
A method to prepare a composite laminate object containing an extrusion grade 7xxx Al substrate and a fiber-reinforced polypropylene layer adhesively laminated to the substrate; is provided. The process includes shaping and cutting an extruded 7xxx aluminum to a profile, assembling a layered arrangement of the 7xxx Al profile as substrate, an adhesive film and a fiber reinforced polypropylene preform, heating the layered arrangement to a temperature of 160-175° C. to melt the polypropylene and activate the adhesive film, applying pressure to at least a surface of the fiber reinforced polypropylene preform to mold the preform to the shape of the extruded 7xxxAl substrate and obtain a semi-finished laminate object, cooling the semi-finished laminate object to 90° C., optionally, cooling the semi-finished laminate object to room temperature for inventory storage; heat treating the semi-finished laminate object at 90° C. for 2 to 8 hours; and then heat treating the semi-finished laminate object at 130° C. to 150° C. for 8 to 16 hours; and cooling the heat treated object to obtain the composite laminate object.
1. A method of making a composite laminate object, the composite laminate object comprising an extrusion grade 7xxx Al substrate and a fiber reinforced polypropylene layer adhesively laminated to the 7xxx Al substrate, the method comprising:
shaping and cutting an extruded 7xxx aluminum member to form a 7xxx Al substrate having a shape;
assembling a layered arrangement of the 7xxx Al substrate, an adhesive film and a fiber reinforced polypropylene preform, wherein the fiber reinforced polypropylene preform comprises reinforcing fibers and polypropylene resin;
heating the layered arrangement to a temperature of 160° C. to 175° C. to melt the polypropylene resin and activate the adhesive film;
applying pressure to at least a surface of the fiber reinforced polypropylene preform to mold the fiber reinforced polypropylene preform to the shape of the 7xxx Al substrate and obtain a semi-finished laminate object;
cooling the semi-finished laminate object to 90° C.;
optionally, cooling the semi-finished laminate object to 20° C. to 30° C. for inventory storage;
heat treating the semi-finished laminate object at 90° C. for 2 to 8 hours;
then heat treating the semi-finished laminate object at 130° C. to 150° C. for 8 to 16 hours to provide a heat treated laminate object; and
cooling the heat treated laminate object to obtain the composite laminate object.
2. The method according to claim 1 , wherein the adhesive film comprises a thermoplastic film, a hotmelt thermoplastic film, or a film of thermosetting epoxy resin.
3. The method according to claim 1 , wherein the extruded 7xxx Al member has a tubular shape.
4. The method according to claim 3 , wherein the polypropylene resin does not comprise any of a silicone oil mold release agent, a wax mold release agent and a hydrocarbon oil mold release agent.
5. The method according to claim 1 wherein the extruded 7xxx Al member has an open structure.
6. The method according to claim 1 wherein the 7xxx Al substrate is not heat treated prior to the assembling and heating of the layered arrangement.
7. The method according to claim 1 , wherein the pressure applied to at least a surface of the fiber reinforced polypropylene preform is from 50 to 200 psi.
8. The method according to claim 1 , wherein the adhesive film comprises an epoxy resin.
9. The method according to claim 1 , wherein the reinforcing fibers are selected from the group consisting of glass fibers, carbon fibers, aramid fibers and a combination thereof.
10. The method according to claim 1 , wherein the polypropylene resin is chemically modified to comprise a silane functionality or an anhydride functionality.
11. The method according to claim 1 , wherein the polypropylene resin comprises at least one of graphite particles and metal particles.
12. The method according to claim 1 , wherein a thickness of the extruded 7xxx aluminum member is from 2 mm to 3 mm.
13. The method according to claim 1 , wherein a thickness of the composite laminate object is from 2.8 to 6.2 mm.
14. The method according to claim 1 , wherein after cooling the semi-finished laminate object to 90° C., the semi-finished laminate object is cooled to 20° C. to 30° C., and stored in inventory prior to the heat treatment at 90° C. for 2 to 8 hours and the heat treatment at 130° C. to 150° C. for 8 to 16 hours.