Composite structure repair process

Details Composite structure repair process Composite structure repair process

1999-03-04

2001-01-16

Ball, Michael W. (Department: 1733)

Adhesive bonding and miscellaneous chemical manufacture

Methods

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C156S064000, C156S098000, C356S002000, C382S285000, C382S286000, C382S302000

Reexamination Certificate

active

06174392

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the art of repairing damaged structure, and more particularly to a novel process for determining and repairing damage to a composite layered structure.
BACKGROUND OF THE INVENTION
The use of composite multi-layered materials exhibiting high strength to weight ratios and capable of extended service is particularly exemplified in aircraft construction where composite multi-layered component structures can be compositionally and geometrically tailored to function in substantially all environments encountered during flight. Because of these extreme environmental conditions, however, it is common for damage to occur to such composite structures. As can be appreciated, repairing these multi-layered structures must be such that a repaired portion fully and completely corresponds in integrity to values present prior to the occurrence of the damage. Otherwise, structural failure may occur at the site of repair during operation of an aircraft bearing the repaired composite structure, and such failure may result in loss of life and property.
Present repair methodology for a multi-layered composite structure generally involves, first, locating the damaged area, second, manually marking and removing the damaged area without significant external aid in the topographical measurement and demarcation of the damaged structural portion to be removed, and, third, manually designing and fabricating each replacement layer of a patch destined to replace the removed damaged area, once again without significant external aid in the replication of original structural topographical orientation. In addition to being extremely tedious, labor-intensive and time-consuming work, such present methodology requires significant operator expertise and, consequently, can be subject to significant operator error. As noted above, an error in the repair of a composite structure can lead to potentially critical circumstances. Thus, it is evident that a need is present for provision of operator aid in the repair of multi-layer composite structures.
Accordingly, a primary object of the present invention is to provide a process for repairing damage to a multi-layer composite structure wherein topographical laser measurement of a damaged area is correlated with damage-depth measurement and known component presence to map damaged-area parameters for ultimate removal.
Another object of the present invention is to provide a process for repairing damage to a multi-layer composite structure wherein a microprocessor correlates laser topographical measurement with inputted depth measurement to create a laser pattern projected on the damaged area to be followed in removing damaged material.
Yet another object of the present invention is to provide a process for repairing damage to a multi-layer composite structure wherein a microprocessor topographical and depth correlation is provided to generate projection of a laser pattern on a flat piece of replacement material to enable an operator to cut a replacement patch whose placement replicates substantially all characteristics of the composite structure prior to damage.
These and other objects of the invention will become apparent throughout the description thereof which now follows.
SUMMARY OF THE INVENTION
The present invention is a method for repairing a multi-layered damage area in a multi-layered composite structure where the damage area has a width dimension and a depth dimension and is disposed on a surface of the structure. The method first comprises measuring the depth dimension of the damage area to obtain depth measurement data, and laser scanning the surface of the structure to obtain topographical measurement data of the damage area. This depth measurement data and topographical measurement data are inputted into a microprocessor along with thickness data of each layer and, optionally, locations of any adjacent non-damage area structures that could be damaged during removal of damage area if care is not exercised. All of this information is correlated among itself by the microprocessor to thereby internally produce a three-dimensional display-replica of the damage area and interpolate a two-dimensional pattern of each layer of the damage area and of the surface of the damage area.
The damage area is removed by first projecting by laser a two-dimensional pattern of the damage area thereat on the surface of the structure, and thereafter manually removing the area to produce a void in accord with the projected pattern which includes any non-damaged material above or beneath width expanses of the damage area. Repair of the structure is accomplished by projecting onto respective replacement material a two-dimensional laser image pattern of each layer of the damage area and manually cutting each layer according to the appropriate pattern. The cut layers then are arranged in accord with construction of the removed damage area (e.g. size, shape, orientation of warp direction, etc.) to form a plug that is placed within the void to thereby replace all earlier-removed material. In this manner, accurately constructed and positioned multi-layer composite structure repair is effectuated to equal the construction of the removed damage area and thereby restore strength, durability, and maintainability to the structure.


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Argard. The Repair of Aircraft Structures Involving Composite Materials. Specialised Printing Services Limited. Loughton, Essex, Oct. 1986.

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