Two-Part Liquid Shim Compositions for Aerospace Gap Filling
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Solution Overview
Problem
Existing liquid shim materials are limited in their ability to fill gaps wider than 0.7 mm and do not meet the stringent tolerance requirements of aerospace assembly operations, particularly in terms of curing time and mechanical properties at varying temperatures.
Innovation Solution
The development of epoxy compositions comprising cycloaliphatic polyamine curatives and adducts of unbranched polyetherdiamine with epoxy resin, along with calcium nitrate accelerators, which form two-part compositions suitable for liquid shim applications, allowing for efficient gap filling and curing with enhanced mechanical properties and temperature resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If existing liquid shim materials are used to fill gaps, then the gap filling function is achieved, but the gap width is limited to no bigger than 0.7 mm
Solution Approach 1:
The patent modifies the chemical composition parameters of the liquid shim material by incorporating specific epoxy resins (including nanosilica-modified epoxy resins), curatives, and additives in controlled proportions. This compositional parameter change enables the material to maintain structural integrity and meet tolerance requirements while effectively filling gaps wider than 0.7 mm, thus resolving the contradiction between gap width capability and reliability.
2Productivity
If rapid curing is achieved, then productivity is improved, but curing time control becomes more difficult
Solution Approach 1:
The patent introduces a two-component system where Component A (epoxy resin composition) and Component B (curative composition) act as intermediaries that control the curing reaction rate. The curative composition contains specific amines and catalysts that mediate the crosslinking reaction, enabling rapid curing when mixed while maintaining separate storage stability. This intermediary approach allows controlled rapid curing that improves productivity without excessive loss of pot life.
Solution Approach 2:
The patent optimizes the molecular weight, functionality, and chemical structure parameters of the curative agents and catalysts to control reaction kinetics. By adjusting these chemical parameters, the material achieves rapid curing (reducing curing time) while the two-part formulation maintains adequate pot life for application, thus resolving the contradiction between curing speed and time loss.
3Strength
If mechanical strength is improved, then reliability is improved, but the material becomes more sensitive to temperature variations
Solution Approach 1:
The patent creates a composite material system combining epoxy resins with nanosilica particles, various curatives, and functional additives. This composite structure provides enhanced compression strength through the synergistic effect of the epoxy matrix and nanosilica reinforcement, while the specific composition ratio and crosslinking structure maintain dimensional stability and resistance to temperature variations, thus resolving the contradiction between strength improvement and temperature sensitivity.
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 compositions demonstrate rapid curing, high compression strength, and resistance to solvents and oils, meeting Airbus AIMS qualification standards, with improved pot life and mechanical properties at low and high temperatures, enabling effective use in aerospace assembly.
Implementation Method 1
an epoxy curative comprising at least one cycloaliphatic polyamine curative and at least one second curative selected from a) an aliphatic polyamidoamine
Implementation Method 2
form crosslinked polymer networks
Implementation Method 3
In some embodiments, the epoxy curative additionally comprises at least one calcium nitrate accelerator
Implementation Method 4
In some embodiments, the epoxy component additionally comprises a core-shell impact modifier
Implementation Method 5
In some embodiments, the epoxy component comprises tetraglycidyl meta-xylenediamine
Implementation Method 6
In some embodiments, the epoxy component comprises an epoxy novolac resin
Data Source
AI summary
Epoxy curatives and two-part compositions comprising epoxy curative and epoxy resin parts are provided as well as methods of their use in liquid shim applications. Epoxy curatives comprise at least one cycloaliphatic polyamine curative and at least one second curative selected from a) an aliphatic polyamidoamine and b) an adduct of an excess of an unbranched polyetherdiamine with an epoxy resin.