Internal Stringer Inspection System for Composite Parts
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Solution Overview
Problem
Composite materials in aerospace structural applications, such as hollow 'hat'-type stringers, are difficult to inspect due to their inaccessible interior, which limits the effectiveness of conventional non-destructive inspection methods.
Innovation Solution
An inspection apparatus comprising a first and second plug, and a trolley positioned between them, forming a leak-proof seal within the composite part, with an elongated actuation element to move the trolley and inspection probes for internal testing, and the option to fill the space between the plugs with liquid for immersion inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-destructive inspection equipment is used, then inspection of accessible areas is possible, but inspection of inaccessible interior areas of hollow stringers cannot be performed
Solution Approach 1:
Instead of bringing inspection equipment to the exterior accessible areas, the invention inverts the approach by inserting inspection probes inside the hollow stringers through access holes. The inspection system moves from external to internal inspection, allowing examination of bond lines and interior surfaces that are otherwise inaccessible to conventional equipment.
Solution Approach 2:
The inspection probes are nested within the hollow stringer structure itself. The probes fit inside the existing hollow interior of the stringers, utilizing the available internal space for inspection operations without requiring external access to the bond lines between stringers and ribs.
2Ease of operation
If pipeline inspection pigs are used, then tubular structures can be inspected from inside, but they require liquid-filled environments and cannot limit immersion fluids to specific areas
Solution Approach 1:
The inspection system segments the hollow stringer interior into specific inspection zones using removable plugs. Each plug seals a particular area, allowing immersion fluid to be introduced only into the desired inspection section rather than filling the entire stringer length. This enables targeted inspection of specific bond lines or areas without managing large volumes of fluid throughout the structure.
Solution Approach 2:
The removable plugs act as intermediaries that control fluid containment. Rather than requiring the entire structure to be filled with fluid, the plugs create isolated chambers that allow immersion inspection to be performed in specific zones. The plugs mediate between the need for fluid immersion and the desire to limit fluid volume and location.
3Weight of moving object
If hollow hat-type stringers are used in integrated structures, then weight and manufacturing costs are reduced, but inspection of stringer-rib bond lines becomes difficult
Solution Approach 1:
The hollow stringer structure, which provides weight savings, is made to serve its own inspection needs. The internal cavity that contributes to weight reduction also serves as the inspection pathway, allowing probes to access bond lines from the interior. The structure's own geometry becomes the inspection channel, eliminating the need for additional external access features.
Solution Approach 2:
Access holes are incorporated into the design during the preliminary manufacturing stage, allowing future inspection operations. These holes are created before final assembly or service, enabling insertion of inspection probes into the hollow stringers for bond line examination without requiring post-manufacturing modifications or compromising structural integrity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise and thorough inspection of composite parts by allowing the inspection probes to operate within the composite structure, overcoming the limitations of conventional methods by providing a controlled environment for inspection and positioning of probes.
Implementation Method 1
filling a space between the first and second plugs with a liquid, such that liquid is trapped between the first and second plugs and surrounds the trolley and the at least one inspection probe
Data Source
AI summary
An inspection apparatus and method for inspecting an interior surface of a hollow composite part. The inspection apparatus may have a first plug, a second plug, and a trolley positioned between the first and second plugs. The first and second plugs may form a leak-proof seal against the interior surface of the hollow composite part. The trolley may support at least one inspection probe for testing the interior surface of the composite part. A method of inspecting the composite part may include the steps of inserting the inspection apparatus into the hollow composite part, pushing or pulling the inspection apparatus with an elongated actuation element to a desired area to be inspected within the composite part, then filling a space between first and second plugs with a liquid. Finally, the method may include a step of inspecting the interior surface of the hollow composite part with the inspection probe.