Thermographic Inspection of Uncured Composite Laminates
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Solution Overview
Problem
Current methods for detecting flaws in uncured composite laminates are time-consuming and expensive, as they require curing and subsequent inspection, followed by costly and labor-intensive repair processes.
Innovation Solution
A system utilizing a heat source and digital thermographic camera to apply a burst of heat and capture thermal images, analyzing temperature derivatives to identify defects like disbonds and inclusions before curing, allowing for early detection and repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional curing and inspection methods are used, then defect detection is achieved, but the process is time-consuming and expensive
Solution Approach 1:
The patent applies preliminary action by performing thermographic inspection on green composite materials before curing. The thermal camera detects defects in the uncured state, allowing early identification of disbonds and inclusions. This preliminary detection avoids the time-consuming cycle of curing followed by inspection and potential rework, directly resolving the contradiction between detection accuracy and inspection time.
2Measurement precision
If curing is performed before inspection, then defect detection is possible, but costly rework is required when defects are found
Solution Approach 1:
The invention performs defect detection in the green (uncured) state before final curing, enabling preliminary identification of defects. This timing allows for straightforward repairs such as adding more material or adjusting layup, rather than expensive post-curing repairs that require cutting, grinding, and patching. The principle of preliminary action thus resolves the contradiction between detection capability and manufacturing ease.
3Measurement precision
If thermographic inspection is applied to cured materials, then defects can be detected, but the inspection process becomes more complex
Solution Approach 1:
The patent applies parameter changes by inspecting materials in their green (uncured) state rather than cured state. The uncured material has different thermal properties that enhance defect detectability with simpler thermal patterns. This parameter change (timing of inspection relative to curing) improves detection accuracy while reducing the complexity of the thermal excitation and analysis required, as cured material inspection often demands more sophisticated multi-frequency or phased-array techniques.
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 faster and cheaper detection and repair of defects in uncured composite laminates, reducing the need for extensive curing and rework, thereby saving time and resources.
Implementation Method 1
A burst of heat is applied to a surface of a plurality of uncured compacted composite layers
Implementation Method 2
At least one digital thermographic image of the surface of the uncured compacted composite layers is captured
Data Source
Figure 1A~1C
Figure 2
Figure 3
AI summary
Method and apparatus for detecting defects in a laminate of uncured, compacted composite sheets. After a number of plies of composite sheets are arranged and compacted, a burst of heat energy is applied to a top surface of the laminate and a digital thermographic camera captures images of the top surface. A computer processor measures heat characteristics of the top surface to identify regions of the top surface with different heat characteristics. Such different areas are identified as regions that include a defect. The defect regions can be repaired by applying additional compaction and/or by removing at least a portion of some layers, removing any foreign object debris, replacing the layers, and compacting the replaced layers. After any defects are addressed, the laminate is cured.