Search

EP-4434731-B1 - TOOLS AND METHODS FOR FABRICATION OF THERMOPLASTIC PANELS

EP4434731B1EP 4434731 B1EP4434731 B1EP 4434731B1EP-4434731-B1

Inventors

  • Sasal, Feride Nur
  • TURKARSLAN, Ozlem

Dates

Publication Date
20260506
Application Date
20240116

Claims (15)

  1. A tool (100) for fabrication of a thermoplastic panel (200), comprising: a sealed vessel (102) defining a volume (104), the sealed vessel (102) comprising a first fluid port (106) and a second fluid port (108); a membrane (110) disposed within the volume (104) to define a first chamber (112) and a second chamber (114), the first chamber (112) configured to receive a first skin (202) and a core (204) of the thermoplastic panel (200) and configured to selectively apply a first fluidic pressure to the first skin (202) and the core (204) in response to receiving a first fluid via the first fluid port (106), the membrane (110) configured to abut a major surface (206) of the thermoplastic panel (200) and the second chamber (114) configured to selectively apply a second fluidic pressure to the membrane (110) in response to receiving a second fluid via the second fluid port (108); and a heater (116) configured to selectively direct heat toward the first chamber (112).
  2. The tool of Claim 1, wherein the membrane (110) comprises a metal alloy.
  3. The tool of Claim 1 or 2, wherein the core (204) comprises at least one of an air permeable thermoplastic foam and an air permeable thermoplastic honeycomb structure (300), in particular wherein the air permeable thermoplastic honeycomb structure (300) comprises an array of hollow cells (302) orthogonal to the first skin (202), the array of hollow cells (302) formed by cell walls (304), the cell walls (304) having a plurality of breather holes (306) such that the air permeable thermoplastic honeycomb structure (300) is air permeable from cell to cell.
  4. The tool of any of Claims 1 to 3, wherein the first fluid comprises at least one of a dry air, an inert gas and a nitrogen gas.
  5. The tool of any of Claims 1 to 4, wherein the second fluid comprises at least one of a dry air, an inert gas, a nitrogen gas, a mineral-based oil and a synthetic-based oil.
  6. The tool of any of Claims 1 to 5, wherein the heater (116) is disposed below the second chamber (114).
  7. The tool of Claim 6, the tool (100) further comprising: a heating controller (124) in operative communication with the heater (116) to selectively apply electrical power to the plurality of electric cartridge heaters (402) after the second fluid is received by the second chamber (114) and after the first fluid is received by the first chamber (112), and wherein the heating controller (124) is configured to remove electrical power from the plurality of electric cartridge heaters (402) after the first skin (202) and the core (204) of the thermoplastic panel (200) are fusion bonded at a bond line (216) between the first skin (202) and the core.
  8. The tool of Claim 7, wherein the heating controller (124) is configured to remove electrical power from the plurality of electric cartridge heaters (402) based at least in part on a predetermined heating time, in particular wherein the predetermined heating time ranges between at least one of about 35 seconds and about 95 seconds, about 50 seconds and about 80 seconds and about 60 seconds and about 70 seconds.
  9. The tool of Claim 6 or 7, the sealed vessel (102) further comprising: at least one temperature sensor (126) within the first chamber (112) and proximate to the bond line (216) between the first skin (202) and the core (204), wherein the heating controller (124) is in operative communication with the at least one temperature sensor (126) and configured to remove electrical power from the plurality of electric cartridge heaters (402) based at least in part on a temperature signal from the at least one temperature sensor (126) indicating a predetermined temperature associated with creating a fusion bond is detected proximate to the bond line (216), in particular wherein the predetermined temperature ranges between at least one of about 240 °C and about 280 °C, about 250 °C and about 270 °C, about 255 °C and about 265 °C, about 310 °C and about 350 °C and about 335 °C and about 375 °C.
  10. The tool of any of Claims 1 to 9, wherein the heater (116) is configured to selectively heat a bond line (216) between the first skin (202) and the core (204) of the thermoplastic panel (200) to a predetermined temperature associated with creating a fusion bond at the bond line (216).
  11. The tool of Claim 10, wherein the sealed vessel (102) further comprises: an inlet fluid port (128); and an outlet fluid port (130), and wherein the tool (100) further comprises: a heat exchanger (132) comprising a plurality of cooling channels (502) in fluid communication with the inlet fluid port (128) and the outlet fluid port (130), the heat exchanger (132) disposed proximate to the heater (116) on an opposing side of the heater (116) in relation to the first chamber (112), the heat exchanger (132) configured to transfer heat from the bond line (216) of the thermoplastic panel (200) to a working fluid flowing through the plurality of cooling channels (502) in response to receiving the working fluid via the inlet fluid port (128).
  12. The tool of Claim 11, wherein the heat exchanger (132) is configured to route the working fluid through the plurality of cooling channels (502) and out the outlet fluid port (130).
  13. The tool of any of Claims 1 to 12, the sealed vessel (102) further comprising: a lid (134) configured to open the sealed vessel (102) to provide access to the first chamber (112) for positioning the first skin (202) and the core (204) inside the first chamber (112) and configured to close to seal the first chamber (112), in particular wherein the heater (116) is disposed above the first chamber (112) within the lid (134).
  14. A method for fabrication of a thermoplastic panel (200), comprising: selectively applying (902) a second fluid pressure to a membrane (110) supporting the thermoplastic panel (200), wherein the thermoplastic panel (200) comprises a first skin (202) and a core (204) previously positioned within a sealed vessel (102) divided into a first chamber (112) and a second chamber (114) by the membrane (110), the second fluid pressure being within the second chamber (114), wherein the second fluid pressure is based on a predetermined tool pressure of a second fluid supplied to the second chamber; selectively applying (904) a first fluid pressure to the first skin (202) and the core (204) in the first chamber (112), wherein the first fluid pressure is based on a predetermined tool pressure of a first fluid supplied to the first chamber; and selectively directing (906) heat toward the first chamber (112) to heat a bond line (216) between the first skin (202) and the core (204) to a predetermined temperature associated with creating a fusion bond at the bond line (216); the method further comprising: supplying the first fluid to the first chamber (112) in response to at least one of activating a first fluid source, opening a supply line to the first chamber (112), regulating a supply pressure for the first fluid to the predetermined tool pressure and opening a fluid port associated with the first chamber (112); and supplying the second fluid to the second chamber (114) in response to at least one of activating a second fluid source, opening a supply line to the second chamber (114), regulating a supply pressure for the second fluid to the predetermined tool pressure and opening a fluid port associated with the second chamber (114).
  15. The method of claim 14, wherein the thermoplastic panel also comprises a second skin, the first fluid pressure is also selectively applied to the second skin and the heat is also selectively directed to heat a second bond line between the second skin and the core to the predetermined temperature, the method further comprising: stopping the directing of the heat associated with the first skin toward the first chamber after the bond line between the first skin and the core of the thermoplastic panel reaches the predetermined temperature; stopping the directing of the heat associated with the second skin toward the first chamber after the second bond line between the second skin and the core of the thermoplastic panel reaches the predetermined temperature; transferring heat from the bond line to a working fluid flowing through a heat exchanger; and transferring heat from the second bond line to a second working fluid flowing through a second heat exchanger; wherein the method further comprises: releasing the first fluid pressure from the first chamber (112); releasing the second fluid pressure from the second chamber (114); opening a lid (134) of the sealed vessel (102) to gain access to the first chamber (112); and removing the thermoplastic panel (200) from the first chamber (112).

Description

FIELD The present disclosure relates generally to thermoplastic panels and, particularly, to various tools and methods for fabrication of thermoplastic panels. Examples of a thermoplastic panel include a thermoplastic sandwich panel and a thermoplastic single skin panel. The tools and methods for fabrication of a thermoplastic panel apply pressures and heat to fusion bond the skin of the panel to the core in a non-isothermal manner. Applications to various thermoplastic materials are contemplated. Likewise, fabrication using various pressures, temperatures, and control mechanisms are also contemplated. BACKGROUND Fabrication of thermoplastic sandwich structure results in delamination of the thermoplastic composite skin when low external pressure is applied to the sandwich during attempts at fusion bonding. Conversely, the application of higher pressures results in core crush or deformation because the process temperature is above the melting temperature (for semicrystalline polymer) or the glass transition temperature (for amorphous polymer) of the thermoplastic core material. Additionally, the process window for fusion bonding of a skin to the core is limited on the one hand by a weak bond strength at low temperatures and on the other hand by core collapse and skin delamination at higher temperatures. Under these circumstances, isothermal manufacturing methods (e.g., use of an oven or an autoclave) cannot be used to join the skins and core of the thermoplastic sandwich. Moreover, current use of non-isothermal methods in fusion bonding results in uncontrolled bond line homogeneity. Accordingly, those skilled in the art continue with research and development efforts to improve the design of tools for fabrication of thermoplastic panels to streamline manufacturing and to implement more consolidated manufacturing processes. Document EP 2 457 718 A2, according to its abstract, states methods and apparatus for fabricating adhesive bonded joints while minimizing the voids and/or porosity found in the cured bondline. The apparatus comprises an evacuation chamber combined with a pressure inducing device to produce bonded joints. The surfaces to be bonded are continuously evacuated throughout the bonding process (pre-mating, mating, debulking and cure). Continuous evacuation is provided via standard vacuum, while the induced pressure can be pneumatically or mechanically provided. Document EP 1 504 889 A2, according to its abstract, states composite sandwich panels that include a core having a permeable body that is sandwiched between two skins. An internal barrier is located between the skins and the core to provide an impermeable chamber surrounding the permeable core. The chamber is pressurized during formation of the panel to provide an interior counter pressure against the mold/press used to form the panel. The counter pressure applied by the chamber reduces the amount of voids in the skins and improves the surface finish of the skins. In addition, the impermeable material remains within the finished panel to provide an internal barrier surrounding the core. In paragraphs [0024] to [0029], this document states that in a partial view of an assembly of core, barrier and skins is shown in place within a press in FIG. 3. A backup tool is provided that may be heated or cooled, as necessary, without heating or cooling the press. In addition, a shell tool is provided as an aid for handling the panel materials before and after they are placed into the press. The core is in the form of an egg crate structure that is made from a plastic material, such as polyamide 6/6. There is no need to perforate the egg crate to provide core permeability because the shape of the egg crate inherently allows a uniform counter pressure to be applied outwardly against the press. A barrier completely surrounds the core. The barrier is also made from a plastic material, such a polyamide 6/6 that melts at a temperature greater than the molding process temperature. The barrier extends out past the edge of the core and is compression sealed, heat-sealed or otherwise sealed as shown at to provide a closed bag or Chamber in which the core is located. An inlet is located through the press and barrier to provide for the introduction of gas or liquid to pressurize the Chamber defined by the impermeable barrier. Skins are located between the barrier and the Shell tool. The skins are made from a composite material, such as Nylon 6/Eglass. The panel construction composed of the materials just described is easily recyclable since all the plastic components are of the same family. During the molding process, the press is forced together as represented by arrows to provide an inward molding pressure (clamp tonnage) against the skins. At the same time, the impermeable chamber formed by barrier is pressurized with a counter pressure as represented by arrows. The outward counter pressure is generally less than the inward molding pressure or clamp tonnage. Th