Nutplate Bonding Fixture With Localized Rapid Adhesive Cure
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Solution Overview
Problem
The long curing time of adhesives used in bonded hardware, such as nutplates, in the aerospace industry is problematic as it delays aircraft maintenance and production, and accelerated curing methods pose safety hazards due to excessive temperature exposure and flammable environments.
Innovation Solution
A rapid cure system that applies localized heating through the nutplate and into the adhesive bondline, using a heater integrated within a nutplate engagement fixture, with a temperature sensor and controller to manage heat and ensure safe, efficient curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If room temperature curing is used, then adhesive strength is achieved, but curing time is excessively long (24 hours)
Solution Approach 1:
The patent applies temperature parameter changes to accelerate the curing process. By heating the substrate to elevated temperatures (typically 50-150°C depending on adhesive specifications), the chemical reaction rate of the adhesive increases, reducing curing time from 24 hours at room temperature to several hours or less at elevated temperature, while still achieving the required adhesive strength
Solution Approach 2:
The patent performs preliminary heating of the substrate and/or adhesive components before bonding, and maintains temperature during the curing process. This preliminary thermal preparation ensures the adhesive remains in an optimal state for curing throughout the process, preventing premature cooling that would extend cure time
2Loss of time
If supplemental heating is applied to accelerate curing, then curing time is reduced, but temperature control becomes critical to prevent structure damage
Solution Approach 1:
The patent incorporates temperature sensors (such as thermocouples or RTDs) positioned near the bond line to continuously monitor the temperature during curing. This feedback is fed to a controller that adjusts the heating power in real-time, maintaining temperature within specified limits and preventing overheating that could damage the substrate or degrade adhesive properties
Solution Approach 2:
The patent uses thermal interface materials or conductive elements as intermediaries between the heat source and the substrate. These intermediaries ensure uniform heat distribution across the bonding area, preventing localized hot spots that could cause structure damage while still achieving the required cure temperature
3Productivity
If heat is delivered to the bonding area, then curing rate increases, but safety hazards arise from excessive temperature in flammable environments
Solution Approach 1:
The patent applies heating locally only to the bonding area where the adhesive is located, rather than heating the entire workpiece or surrounding area. This localized heating approach minimizes the volume of flammable atmosphere that reaches hazardous temperatures, reducing fire risk while still achieving the required curing rate at the bond line
Solution Approach 2:
The patent employs heat transfer through the substrate or fixture as an intermediary method. Instead of applying heat directly to the adhesive in open air, the heating element warms the substrate which then conducts heat to the adhesive, or a heated fixture transfers heat through contact. This indirect heating method reduces exposed hot surfaces and minimizes fire hazards in flammable environments
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
Significantly reduces nutplate bonding time, enhances adhesive consistency and strength, and ensures safety by controlling temperature and minimizing exposure to hazardous environments.
Implementation Method 1
a heater operable to deliver heat through the nutplate and into the adhesive bondline
Implementation Method 2
the elastomeric tube comprising an elongated tube with an external diameter sized to provide a friction fit with the aperture and retain the elastomeric tube within the aperture
Data Source
AI summary
Systems for positioning and bonding a nutplate to a substrate having an aperture include a nutplate engagement fixture and a temperature sensor retention fixture. The nutplate engagement fixture includes a rigid tube and an elastomeric tube engaged with the rigid tube, the elastomeric tube having an elongated tube sized to provide a friction fit with the aperture and retain the elastomeric tube within the aperture. The rigid tube is operable to engage the nutplate at one end and the elastomeric tube is configured to anchor the nutplate engagement fixture at the aperture and secure the nutplate in contact with the substrate. The temperature sensor retention fixture includes a fixture body sized and configured to engage with the nutplate and at least one passageway within the fixture body sized and configured to allow a temperature sensor to be inserted or embedded therein with an end proximal a surface of the nutplate.