Multiple-layer structures and joining method for honeycomb, foam and lightweight materials

Multiple layers of honeycomb or foam core lightweight materials are bonded together side-by-side to increase strength, to customize strength relationships in relation to form for particular structural components and to provide a base for strong connections to honeycomb and foam structures. Increased strength results from utilizing outside layers as skins for some embodiments with an effect of progressive increase of strength of the core with the multiple layers. Connection strength is provided by formation of connection bays in one or more outside layers to which connection members of structural components are bonded in the connection bays. The outside or distal core layers can be higher density and higher strength than inside core layers for dynamic and impact-related use-conditions in addition to providing a thicker and stronger surface to which other structures and other members can be connected. An aircraft wing constructed using this method illustrates high-density, high-heat and high-impact strength of a contoured distal core in relationship to a low-density contoured proximal core.

BACKGROUND OF THE INVENTION 
This invention relates to lightweight structural members and more 
particularly to multiple layers of honeycomb, foam or similar lightweight 
material members bonded together for increased structural strength and 
improved bonding strength. 
Structural uses of honeycomb and foam construction have been confined 
previously to single layers. Increased advantages of strength-per-weight, 
torsional strength, joining strength, impact strength and other advantages 
related to particular products, however, can be achieved with multiple 
layers of bonded honeycomb members. The aerospace industry is the most 
prolific user of honeycomb construction. There its often greater cost is 
compensated by essential strength-per-weight. Prior use of multiple 
honeycomb layers have been only at joints to join single honeycomb layers 
to other single layers or to other structural members of aircraft. The use 
of multiple layers for increased structural strength in addition to 
increased joining strength and decreased construction cost has not been 
recognized nor developed. U.S. patents describing joining methods with 
variations of multiple layers of honeycomb material include U.S. Pat. No. 
4,671,470 granted to Jonas in June 1987; U.S. Pat. No. 4,395,450 granted 
to Whitener in July 1983; and U.S. Pat. No. 4,416,349 granted to Jacobs in 
November 1983. None of these employed multiple layers except to a limited 
extent at joints. They did not provide the strength of multiple layers 
throughout the structure and at the joints. 
Other methods of joining honeycomb members have included variations of 
potted bolts such as described in U.S. Pat. No. 4,370,372 granted to 
Higgins in 1983; U.S. Pat. No. 4,052,202 granted to Fischer & Fischer in 
1977; and U.S. Pat. No. 3,282,015 granted to Rohe et al. in 1966. Like the 
multiple layers only at joints, the potting methods provide only local 
strength and resulted in decrease of overall strength per weight. 
SUMMARY OF THE INVENTION 
One object of this invention is to increase strength-per-weight of 
honeycomb construction. 
Another object is to decrease cost by decreasing costs of connections for 
honeycomb construction. 
Another object is to increase the uses of honeycomb construction by 
providing higher dynamic-use strength and higher connection strength. 
Another object is to increase the uses of honeycomb construction. 
Particular objects are to provide improved aircraft frame construction, 
aircraft wing construction, aircraft cabinetry, general cabinetry, 
prefabrication of built-in dwelling cabinetry and general cabinetry. 
Multiple layers of honeycomb cores are bonded together side-by-side to 
increase strength, to customize strength relationships in relation to form 
for particular structural components and to provide a base for strong 
connections to honeycomb structures. Increased strength results from 
utilizing outside layers as skins for some embodiments with an effect of 
progressive increase of strength of honeycomb core with the multiple 
layers. Connection strength is provided by formation of connection bays in 
one or more outside layers to which connection members of structural 
components are bonded in the connection bays. The outside or distal 
honeycomb core layers can be higher density and higher strength than 
inside core layers for dynamic and impact-related use-conditions in 
addition to providing a thicker and stronger surface to which other 
structures and other honeycomb members can be connected.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1 and to all FIGS. generally, a proximal honeycomb core 1 
is bonded at opposite sides to proximal core skin 2. A distal core 3 is 
bonded at opposite sides to distal core skin 4. At least one distal core 3 
with distal skins 4 is bonded to either or both proximal core skins 2. 
Either a proximal core skin 2 or a distal core skin 4 can be utilized as a 
common skin between bonded proximal cores 1 and distal cores 3. The distal 
cores 3 and skins 4 function, in effect, as outer skins to the proximal 
core 1. They form an exoskeleton construction for providing increased 
beam-type strength, for attachment of appendages of connecting structures 
and for interface with use-conditions. The workloads of the proximal cores 
1 can be greatly different from the workloads of the distal cores 3 and 
both the cores 1 and 3 and the skins 2 and 4 can be designed appropriately 
different accordingly. 
Referring to all FIGS. except FIG. 5, connection bays in any form such as a 
channel connection bay 5 or an angle connection bay 6 can be provided at 
distal-core channel walls 7 with bay floors 8 at preferably an outside 
surface of proximal skin 2 or, alternatively for some purposes, at an 
inside surface of distal skin 3. Structural connection members 9 
comprising either other honeycomb members such as shelves or shelf-like 
forms 10 or other materials can be sized and shaped to fit snugly into the 
connection bays 5 and 6 and to be bonded there with appropriate bonding 
agents and bonding procedures. 
Referring to FIGS. 2 and 3, other non-honeycomb components such as a 
drawer-slide assembly 11 can be utilized in this honeycomb construction. 
Drawers provide particularly severe dynamic use-conditions for 
conventional honeycomb construction of cabinetry. But with the exoskeleton 
construction and connection strength provided by this invention, more 
demanding use conditions can be designed for with honeycomb construction. 
This is a particular advantage for cabinetry for aerospace vehicles, cars, 
motor homes, boats, prefabricated homes and trailer homes. For all 
cabinetry, it provides particularly sturdy and now long-lasting 
construction under typical use-conditions. FIG. 2 illustrates a 
single-sided attachment and FIG. 3 a double-sided attachment construction. 
Referring to FIG. 4, a spliced panel 12 with a mirror-image fitting 13 of 
another structural member or spliced panel can form a connection bay and 
connection member. This is a form of an angle connection bay. 
Referring to FIG. 5, a section of an airplane wing 14 with a contoured 
inside core 15, also referred to as a proximal core, and matching outside 
contoured core 16, also referred to as a distal core, demonstrate 
construction with proximal and distal honeycomb layers for curved or 
compound-curved forms similar to that shown in FIG. 4. To form such a 
curved wing, one or more proximal layers 15 is sized and shaped to a 
design by selectively cutting or constructing proximal core walls 17 in 
lengths that form the design structure at their terminal ends with the 
wall 17 at right angles to bending and torsional strength requirements of 
the design structure. Then distal core walls 19 also are cut or 
constructed with lengths that shape core surfaces to the contour of the 
proximal core with the distal core walls 18 extended generally at right 
angles to the direction of bending and torsional strength requirements of 
the structure. At positions on curves and bends, distal cores 16 with 
appropriately-angled distal core walls 18 can be positioned at right 
angles to the direction of strength requirements for maximizing structural 
integrity. To accomplish this, some sections may require distal cores 16 
with distal core walls 18 at varying angles from the proximal core walls 
17. This would require wedges or wedge-shaped core walls. However, in the 
case of the airplane wing 14 with near-parallel walls and an 
acutely-curved leading edge 19, the leading edge 19 could be provided with 
leading-edge core walls 20 at right angles to distal core walls 18. 
The leading-edge core walls 20 and a leading-edge core skin 21 could be 
constructed of appropriately heat-resistant and impact-strength materials. 
Differences in materials for proximal cores 15 and distal cores 16 are 
illustrated by different thicknesses of lines representing the respective 
core walls 17 and 18. The distal core walls 18 could be appropriately 
higher in density thicker for particular applications than proximal core 
walls 17. 
Similar design characteristics and principles could be employed for a nose 
cone or for other sections of aerospace-vehicle construction. An airplane 
wing or nose cone could be constructed without either ribs, stringers or 
struts for many low-cost but highly reliable executive and private 
aircraft. To a great extent, the same principles could be employed 
effectively for frame and wing construction as well as for cabinetry 
construction of commercial aerospace vehicles also. 
FIG. 6 illustrates a distal core 3 with dividers, walls or shelves 22 
connected in channel connection bays 5. The dividers, walls or shelves 22 
can be honeycombed or constructed of different materials as indicated by 
the different material cross sections. 
FIG. 7 illustrates variation of thickness relationships of proximal cores 1 
and distal cores 3 in relationship to channel connections bays 5 and angle 
connection bays 6 for different applications. 
Although the preferred embodiments of the present invention have been 
described using honeycomb materials, it can also be applied to other 
lightweight materials, particularly foam core, to increase strength of 
structural members made therefrom. 
It will be apparent to one skilled in the art that a new and useful 
honeycomb construction and methods for use have been described hereinabove 
and that various modifications from the specific details are contemplated 
to fall within the following