Method of diffusion bonding honeycomb composite structures

Claim 1

A method of fabricating a metallic composite structure having a relatively fragile metallic cellular core component sandwiched between and diffusion bonded to upper and lower metallic face sheet components, said cellular core component having individual cells with a controlled atmosphere sealed therein, comprising the steps of: a. assembling the core component between the upper and lower face sheet components in a furnace with the core component resting upon and in surface contact with the lower face sheet component, and with the upper face sheet component spaced above and apart from the core component with glass support means, said glass support means having a fiber softening point at an elevated temperature; b. forming a controlled temperature within the furnace containing the cellular core component and within the individual cells of the cellular core component; c. while substantially maintaining the controlled atmosphere of step (b), elevating the temperature of the furnace containing the components and the glass support means to at least the fiber softening point of the glass support means, whereby the glass support means yield and the upper face sheet component lowers into surface contact with the core component; and d. while substantially maintaining the temperature of step (c), applying a compressive force to the components, said compressive force being less than that which would crush the core component, to diffusion bond the core component to the upper and lower face sheet components along substantially the entire interface therebetween, thereby sealing the controlled atmosphere within the individual cells of the cellular core component.

Claim 3

A method of fabricating a metallic composite structure having a relatively fragile metallic cellular core component sandwiched between and diffusion bonded to two metallic face components comprising the steps of: a. assembling the core component between the two face sheet components in a vacuum furnace with at least one of the face sheet components spaced apart from the core component with glass spacer means, said glass spacer means having a fiber softening point at an elevated temperature; b. evacuating the vacuum furnace to remove contaminants from the components; c. while substantially maintaining the vacuum of step (b), elevating the temperature of the vacuum furnace containing the components and the glass spacer means to at least the fiber softening point of the glass spacer means; and simultaneously d. applying a compressive force between the two face sheet components and the core component, said compressive force being sufficient to overcome the softened glass spacer means but insufficient to crush the core component; whereby the face sheet components are urged into intimate surface contact with and diffusion bonded to the core component along substantially the entire interface therebetween.

Claim 4

A method of fabricating a metallic composite structure having a relatively fragile metallic cellular core component sandwiched between and diffusion bonded to upper and lower metallic face sheet components comprising the steps of: a. assembling the core component between the upper and lower face sheet components in a vacuum furnace with the core component resting upon and in surface contact with the lower face sheet component, and with the upper face sheet component spaced above and apart from the core component with glass support means, said glass support means having a fiber softening point at an elevated temperature; b. evacuating the vacuum furnace to remove contaminants from the components; c. while substantially maintaining the vacuum of step (b), elevating the temperature of the vacuum furnace containing the components and the glass support means to at least the fiber softening point of the glass support means; whereby the glass support means yield and the upper face sheet component lowers into surface contact with the core component; and d. while substantially maintaining the temperature of step (c), applying a compressive force to the components, said compressive force being less than that which would crush the core component, to diffusion bond the core component to the upper and lower face sheet components along substantially the entire interface therebetween.

Claim 6

A method of fabricating a titanium honeycomb structural panel having an evacuated cellular titanium core component sandwiched between and diffusion bonded to upper and lower titanium face sheet components, said cellular core component having a characteristic cell wall thickness of about 0.001 to 0.002 inch, comprising the steps of: a. assembling the core component between the upper and lower face sheet components in a vacuum furnace with the core component resting upon and in surface contact with the lower fAce sheet component, and with the upper face sheet component spaced above and apart from the core component with glass support means, said glass support means comprising a borosilicate glass having a fiber softening point of about 1, 400* to 1,600* F.; b. evacuating the vacuum furnace to at least 10 3 torr to remove contaminants and to evacuate the cellular spaces of the core component; c. while substantially maintaining the vacuum of step (b), elevating the temperature of the vacuum furnace containing the components and the glass support means to at least the fiber softening point of the glass support means; whereby the glass softens and the upper face sheet component lowers into surface contact with the core component; and then d. additionally elevating the temperature of the vacuum furnace to about 1,700* to 1,800* F. and applying a compressive force to the components of about 10 p.s.i. to 15 p.s.i. at the interface of the core component and the face sheet components to diffusion bond the core component to the upper and lower face sheet components along substantially the entire interface therebetween, thereby sealing the evacuated cell spaces of the cellular core component.