Test Coupons for Node Bond Durability Prediction
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Solution Overview
Problem
It is challenging to predict the durability of node bonds in honeycomb structures under extreme conditions due to the time-intensive and costly process of simulating thermo-mechanical loading in laboratory settings, which is crucial for assessing the service life of aerospace components like aircraft.
Innovation Solution
The development of test coupons with node bonds and related apparatuses and methods that allow for cyclic and static loading to determine the durability of node bonds, using finite element analysis and strain energy release rate calculations to estimate the service life, enabling equivalent damage modeling and accelerated testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laboratory simulations of thermo-mechanical loading are conducted to predict node bond durability, then measurement precision is improved, but loss of time increases significantly
Solution Approach 1:
The patent creates a simplified test coupon that copies only the essential node bond structure (adhesive stripes between foils) without the complex honeycomb geometry. This allows laboratory simulation to focus on the critical bonding interface, achieving durability prediction accuracy while reducing testing time from months/years to feasible durations.
Solution Approach 2:
The invention segments the honeycomb structure into its fundamental bonding element (node bond between adjacent foils). By isolating and testing individual node bonds in simplified coupon form, the patent enables precise durability measurement without requiring to simulate entire honeycomb panels through extreme thermal cycles.
2Reliability
If extensive laboratory simulations are performed to assess service life, then reliability is improved, but productivity decreases
Solution Approach 1:
The test coupon serves as a simplified copy that replicates the critical node bond behavior without the full honeycomb structure. This copying approach maintains reliability of service life predictions by focusing on the adhesive bonding mechanism, while dramatically improving productivity by reducing test complexity and duration.
Solution Approach 2:
The patent performs preliminary action by creating simplified test coupons before conducting extensive durability testing. This preliminary simplification allows rapid assessment of node bond reliability under various conditions, improving overall testing efficiency while maintaining prediction accuracy.
3Adaptability or versatility
If dissimilar materials are used in outer panels and honeycomb core, then adaptability is improved, but object-generated harmful factors increase due to residual stresses
Solution Approach 1:
The patent extracts the node bond interface from the complete honeycomb structure and tests it in isolation using dissimilar material foils. This extraction allows direct observation and measurement of residual stress effects at the bonding interface without the confounding factors of the full structure, enabling better understanding and mitigation of harmful residual stresses while maintaining material selection flexibility.
Data Source
AI summary
A test coupon having node bonds is disclosed. In some aspects, the method includes a first foil and a second foil, stripes of adhesive serially disposed across a width of the first foil or the second foil and coupling the first foil and second foil to one another to form node bonds, and a first adherend coupled to the first foil and a second adherend coupled to the second foil such that the first foil and the second foil are provided between the first adherend and the second adherend, the first adherend and the second adherend being connectable to load blocks of a test apparatus capable of loading the test coupon to determine characteristics of each of the node bonds formed from the stripes of adhesive. A method for testing node bonds and a related apparatus are also disclosed.