Self-Propelled Inspection Probe for Hollow Composite Stringers
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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 inaccessible locations, and existing non-destructive inspection methods are inadequate for complex integrated structures, especially when conventional equipment cannot reach critical areas within these structures.
Innovation Solution
An inspection apparatus comprising a support frame, an inspection probe with a conforming solid material and a pre-wetting apparatus, which allows for wireless signal transmission, such as ultrasound waves, through a thin layer of liquid on the inner surface of the composite part, enabling effective inspection of inaccessible areas without flooding the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional NDI equipment is used to inspect composite parts, then inspection of accessible areas is possible, but inaccessible locations such as interior surfaces of hollow stringers cannot be inspected
Solution Approach 1:
The inspection apparatus is inserted inside the hollow composite structure (stringer) and inspects the interior surfaces from within, reversing the conventional approach where inspection equipment approaches surfaces from the outside. This allows access to interior surfaces of hollow stringers and other inaccessible areas that cannot be reached by conventional external inspection methods.
Solution Approach 2:
The inspection apparatus is designed to be inserted within the hollow composite structure, with the inspection probe positioned inside the stringer cavity. The apparatus nestles within the existing structure to perform inspection from the interior, enabling access to surfaces that are otherwise inaccessible from the exterior.
2Adaptability or versatility
If pipeline inspection pigs are used in liquid-filled environments, then tubular structures can be inspected, but water cannot be limited to specific areas and may enter undesired components
Solution Approach 1:
The pre-wetting apparatus applies liquid coupling medium only locally at the inspection interface between the transducer and the composite surface, rather than flooding the entire structure. The liquid is contained to the immediate inspection area, providing adequate acoustic coupling without allowing water to enter undesired components or sections of the structure.
Solution Approach 2:
A conformal solid material (such as ultrasound gel or rubber) is introduced as an intermediary between the transducer and the composite surface. This material maintains acoustic coupling for ultrasound transmission while preventing liquid from penetrating into the composite structure, thereby protecting components from water damage while enabling effective inspection.
3Measurement precision
If ultrasound inspection requires liquid coupling, then acoustic coupling is achieved, but excessive liquid may damage composite structures or enter fastener holes
Solution Approach 1:
The pre-wetting apparatus delivers liquid coupling medium in a controlled, localized manner only at the transducer interface, ensuring adequate acoustic coupling for ultrasound transmission while preventing excess liquid from spreading to sensitive areas such as fastener holes or composite joints where it could cause damage.
Solution Approach 2:
The conformal solid material serves as a protective intermediary layer between the liquid coupling medium and the composite structure. It transmits ultrasound signals effectively while acting as a barrier that prevents liquid from penetrating into the composite material or entering fastener holes, thereby eliminating the risk of structural damage from water exposure.
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
The apparatus enables thorough non-destructive inspection of composite parts by providing acoustic coupling and positioning the inspection probe within the structure to detect defects, ensuring minimal fluid usage and maintaining structural integrity by avoiding water entry into undesired sections.
Implementation Method 1
The inspection probe may send and receive wireless signals, such as ultrasound waves, for inspecting an inner surface of a composite part
Implementation Method 2
The conforming solid material may propagate the wireless signals from the inspection probe therethrough
Implementation Method 3
The pre-wetting apparatus may be a weeping sponge or similar apparatus
Data Source
AI summary
An inspection apparatus and method for inspecting an inner surface of a hollow composite part. The inspection apparatus may have a support frame, at least one transducer attached to the support frame, an ultrasound gel pad attached to an outer surface of the transducer, and a sponge attached to the support frame. The transducer may send and receive ultrasound waves and the sponge may be positioned to leave a trail of water when moved along the inner surface of the hollow composite part, such that the water rests between the ultrasound gel pad and the inner surface once the inspection apparatus reaches a location to be inspected. The ultrasound waves may thus be transmitted through the ultrasound gel pad and then through the water before bouncing off of the inner surface of the hollow composite part. The ultrasound waves bounced off of the inner surface may be detected by the transducer and analyzed to determine if there is a defect in the composite part.