# US 9,751,287 B2 · Low energy process for making curved sandwich structures with little or no residual stress > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,751,287 B2 - Document ID: US9751287B2 - Status: Granted - Kind: B2 - Application number: 14/255,389 - Filed: 2014-04-17 - Published: 2015-10-22 - Granted: 2017-09-05 - Earliest claimed: 2014-04-17 - Assignees: GM Global Technology Operations LLC - Applicants: GM Global Technology Operations LLC - Inventors: Jacob M. Hundley; Nilesh D. Mankame; Eric C. Clough; Alan J. Jacobsen; Elisabeth J. Berger - Web page: https://patentgrep.com/patent/US9751287B2 ## CPC - B32B 37/02: characterised by a sequence of laminating steps, e.g. by adding new layers at consecutive laminating stations - B32B 15/04: comprising metal as the main or only constituent of a layer, {which is} next to another layer of {the same or of} a {different material (next to a bituminous or tarry layer B32B11/08; next to a water-setting substance layer B32B13/06; next to a glass layer B32B17/061; next to a cellulosic plastic layer B32B23/042)} - B32B 27/06: as the main or only constituent of a layer, {which is} next to another layer of {the same or of} a {different material (next to a layer of a particular substance B32B9/045; next to a bituminous or tarry layer B32B11/046; next to a water setting substance layer B32B13/12; next to a metal layer B32B15/08; next to a glass layer B32B17/10; next to a layer formed of natural mineral fibres or particles B32B19/045; next to a wood layer B32B21/08; next to a cellulosic plastic layer B32B23/08; next to a natural or synthetic rubber layer B32B25/08)} - B32B 27/20: using fillers, pigments, thixotroping agents - B32B 38/1866: {conforming the layers or laminate to a convex or concave profile} - B60R 21/34: Protecting non-occupants of a vehicle, e.g. pedestrians {(B60R19/02 takes precedence)} - B32B 37/146: {whereby one or more of the layers is a honeycomb structure} - B32B 2250/03: 3 layers - B32B 2250/40: Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA - B32B 2262/101: Glass fibres - B32B 2262/106: Carbon fibres, e.g. graphite fibres - B32B 2310/0831: using UV radiation - B32B 2605/003: Interior finishings - B60R 2021/343: {using deformable body panel, bodywork or components} - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM - B60R: VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR ## Abstract A process for fabricating a curved beam including a micro-truss structure. In one embodiment, the process includes fabricating the micro-truss structure on a bottom facesheet, where the micro-truss structure is only partially cured so that it is readily bendable, and then forming the partially cured micro-truss structure and bottom facesheet over a curved fixture, where the partially cured micro-truss structure is then fully cured and hardened to its final curved state. A top facesheet is then adhered to a top surface of the micro-truss structure. In an alternate embodiment, a curved bottom facesheet is forced flat against a fixture and the micro-truss structure is formed while the bottom facesheet is secured to the fixture to a partially cured state. The bottom facesheet is then released from the fixture, which causes it to return to its curved configuration causing the micro-truss structure to bend. ## Claims ### Claim 1 A method for fabricating a curved sandwich structure, said method comprising: providing a flat bottom facesheet, wherein the bottom facesheet is comprised of a curable material in a partially cured format so it is easily bendable; positioning a mold in contact with the bottom facesheet so that the mold and the bottom facesheet define an enclosure; filling the enclosure with a liquid photo-monomer resin; positioning a mask with patterned apertures relative to the mold; irradiating the liquid photo-monomer resin in the enclosure through the apertures in the mask with collimated UV light from a plurality of sources to form a partially cured micro-truss structure having a plurality of interconnected self-propagating photopolymer waveguides in a lattice configuration coupled to the bottom facesheet; removing uncured liquid photo-monomer resin from the mold; removing the mold from the partially cured micro-truss structure and the bottom facesheet; conforming the bottom facesheet to a curved fixture so that the bottom facesheet is bent to the shape of the curved fixture and the partially cured micro-truss structure bends in association with the bottom facesheet; fully curing the micro-truss structure and the bottom facesheet to a rigid state while they are conformed to the shape of the fixture; and attaching a top facesheet having a complimentary curvature to the now curved micro-truss structure and bottom facesheet to form the sandwich structure. ### Claim 2 (depends on 1) The method according to claim 1 wherein the bottom facesheet and the top facesheet are selected from the group consisting of aluminum alloys, carbon fiber composites, metals alloys, steels, thermoplastic polymers and glass fiber composites. ### Claim 3 (depends on 2) The method according to claim 2 wherein the top facesheet and the bottom facesheet are formed of different materials. ### Claim 4 (depends on 1) The method according to claim 1 wherein fully curing the micro-truss structure includes providing multiple exposures to UV light. ### Claim 5 (depends on 1) The method according to claim 1 wherein fully curing the micro-truss structure includes employing an elevated temperature thermal cure. ### Claim 6 (depends on 1) The method according to claim 1 wherein the bottom facesheet includes edge walls that contact the top facesheet to form an enclosed sandwich structure. ### Claim 7 (depends on 1) The method according to claim 1 wherein the sandwich structure is a vehicle impact beam. ### Claim 8 (depends on 1) The method according to claim 1 wherein fully curing the bottom facesheet includes fully curing the bottom facesheet at the same time that the micro-truss structure is fully cured. ### Claim 9 (depends on 1) The method according to claim 1 wherein fully curing the bottom facesheet includes fully curing the bottom facesheet at a different time than when the micro-truss structure is fully cured. ### Claim 10 (depends on 1) The method according to claim 1 wherein attaching the top facesheet to the micro-truss structure includes gluing the top facesheet to ends of the waveguides at an exposed surface of the micro-truss structure. ### Claim 11 A method for fabricating a curved sandwich structure, said method comprising: providing a flat bottom facesheet; positioning a mold in contact with the bottom facesheet so that the mold and the bottom facesheet define an enclosure; filling the reservoir with a liquid photo-monomer resin; positioning a mask with patterned apertures relative to the mold; irradiating the liquid photo-monomer resin in the enclosure through the apertures in the mask with collimated UV light from a plurality of sources to form a partially cured micro-truss structure having a plurality of interconnected self-propagating photopolymer waveguides in a lattice configuration coupled to the bottom facesheet; removing uncured liquid monomer resin from the mold; removing the mold from the bottom facesheet so as to separate the cured micro-truss structure and the bottom facesheet; heating the micro-truss structure and the bottom facesheet above a predetermined transition temperature so as to cause the micro-truss structure and the bottom facesheet to become pliable; forming the now pliable micro-truss structure and bottom facesheet to a curved mold; lowering the temperature of the micro-truss structure and the bottom facesheet below the predetermined transition temperature to cause the micro-truss structure and bottom facesheet to harden; and securing a top facesheet to the micro-truss structure opposite to the bottom facesheet. ### Claim 12 (depends on 11) The method according to claim 11 wherein the top facesheet and the bottom facesheet are formed of different materials. ### Claim 13 (depends on 11) The method according to claim 11 wherein the sandwich structure is a vehicle impact beam. ### Claim 14 (depends on 11) The method according to claim 11 wherein the bottom facesheet includes edge walls that contact the top facesheet to form an enclosed sandwich structure. ### Claim 15 (depends on 11) The method according to claim 11 wherein securing the top facesheet to the micro-truss structure includes gluing the top facesheet to ends of the waveguides at an exposed surface of the micro-truss structure. ### Claim 16 A method for fabricating a curved sandwich structure, said method comprising: providing a flat bottom facesheet; positioning a mold in contact with the bottom facesheet so that the mold and the bottom facesheet define an enclosure; filling the reservoir with a liquid photo-monomer resin; positioning a mask with patterned apertures relative to the mold; irradiating the liquid photo-monomer resin in the enclosure through the apertures in the mask with collimated UV light from a plurality of sources to form a fully cured micro-truss structure having a plurality of interconnected self-propagating photopolymer waveguides in a lattice configuration coupled to the bottom facesheet; removing uncured liquid monomer resin from the mold; removing the mold from the bottom facesheet so as to separate the cured micro-truss structure and the bottom facesheet; heating the micro-truss structure and the bottom facesheet above a predetermined transition temperature so as to cause the micro-truss structure and the bottom facesheet to become pliable; forming the now pliable micro-truss structure and bottom facesheet to a curved mold; lowering the temperature of the micro-truss structure and the bottom facesheet below the predetermined transition temperature to cause the micro-truss structure and bottom facesheet to harden; and securing a top facesheet to the micro-truss structure opposite to the bottom facesheet. ### Claim 17 (depends on 16) The method according to claim 16 wherein the top facesheet and the bottom facesheet are formed of different materials. ### Claim 18 (depends on 16) The method according to claim 16 wherein the bottom facesheet includes edge walls that contact the top facesheet to form an enclosed sandwich structure. ### Claim 19 (depends on 16) The method according to claim 16 wherein the sandwich structure is a vehicle impact beam. ### Claim 20 (depends on 16) The method according to claim 16 wherein securing the top facesheet to the micro-truss structure includes gluing the top facesheet to ends of the waveguides at an exposed surface of the micro-truss structure.