Introduction
In aerospace manufacturing, there is a key problem- the weight of the aircraft needs to be maintained with respect to its strength. Heavy aircrafts obviously mean that the fuel mileage will fall drastically. So, if we reduce the weight, we also need to ensure that the material strength is not compromised otherwise the overall aircraft will be very risky to fly.
The engineers work constantly to bring an innovative balance of weight and strength. Also, do you know that the NASA reported a 21% weight reduction in Mars rover panels by switching adhesives – but at what cost? In this article, we will further do a deep study and cost-performance breakdown of super glue vs epoxy.
Key Performance Metrics in Aerospace
In the aerospace industry, the manufacturers have to take care of a few key performance metrics that define a well-structured and high-quality product overall. In this section, we’ll discuss these.
- Shear Strength
We can discuss shear strength of a material with its ability to not tear down or get fractured easily when it comes under physical stress. For example, when we stretch or bend a metallic sheet, the molecules of that metal are tightly intact and doesn’t let the sheet break down or tear so easily. That is called its shear strength.
Higher shear strength means high quality. When we are manufacturing any component of an aircraft, a high shear strength is our objective. Otherwise, the aircraft can damage easily. Even a minor defect in the composite materials will bring down the overall performance and quality of he aircrafts, hence indicating a requirement for high shear strength.
The CA: 15-25 MPa super glue becomes a good compound for short-term use because of its moderate shear strength, while Epoxy: 30-45 MPa is a thermally recycled compound with a long-term life and ideal for handling stressful loads in the aircrafts.
- Temperature Tolerance
Temperature is another factor, which indicates that an aircraft will go through all kinds of temperatures and atmospheres, such as tropical regions, snowy, rainforests, and hottest temperatures such as those around the equator or deserts. Aircrafts should be able to handle these temperatures.
When we talk about the fixing compounds like super glue or epoxy, they should stay intact otherwise inability to tolerate temperatures will lead to aircraft breakdown and it can even happen mid air.
If we talk about the super glue or Cyanoacrylate (CA), it has an ideal temperature tolerance of -54 degrees Celsius to 82 degrees Celsius. But if it goes above 120 degrees Celsius, we can expect a breakdown or degradation in the temperature.
Similarly, Epoxy has a normal operating temperature of -73 degrees to 204 degrees Celsius, which is within the aerospace-grade formulations.
- Curing Time
The chemical reactions in Cyanoacrylate are so rapid that they can bring down its curing time to a few seconds. All that’s needed is to keep the two surfaces tightly intact with an exterior force until the Cyanoacrylate cures fully. This method will give the most promising joint and bond that will last for a long time.
When talking about epoxy, it can take up to 24 hours to cure fully but there’s no such need to keep the two surfaces tightly intact. But there are some options like “oven cure” that can bring down the curing time to a few hours in case of epoxy.
Cost Analysis
| Factor | Cyanoacrylate | Epoxy |
| Material Cost Per Liter | $80 to $120 | $150 to $300 |
| Labor Cost (Curing Time) | 0.2 hrs per kg | 1.5-4 hrs per kg |
| Rework Cost | High (brittle bonds) | Low (reversible with heat) |
| QC Testing Cost | Limited non-destructive testing | Mandatory UT/RT inspections |
Application Scenarios
Cyanoacrylate Best For
The super glue is ideal for interior repairing where the cured glue will not be exposed to harsh weather conditions. For example, using it for repairing interior components like cabins, seats, or anything that is not directly a structure of the aircraft, the super glue would be an excellent choice for repairs.
It will be cost efficient, quick, and will give you a temporary fixing solution until the aircraft can be taken to a professional mechanic for professional and promising repairs like welding.
Epoxy Best For
The direct structure of any aircraft that needs to be repaired should be repaired with epoxy instead of super glue because epoxy can handle much more vibrations than super glue. On top of that, the bond strength of epoxy is much better than super glue and it can handle harsh weather conditions, which is why any exterior damages or damages to the structure of the aircraft can be repaired easily using epoxy. It can take more time to cure but it’s worth it.
Critical Consideration
There is a certification FAA AC 20-107B compliance for composite repairs, which states that the selection of material that we use in the aircraft repairs should be certified by this certificate. It is a standard for the repair materials that we will use to repair the aircrafts. For example, we can’t use just any regular super glue or epoxy in aircrafts because they need to be certified and be of the standards suggested by this FAA AC 20-107B compliance for composite repairs.
Cyanoacrylate vs Epoxy Aerospace Case Studies
- High Shear Strength Adhesive for Composites
Problem Identification
The bonding of the structural components of SpaceX Falcon 9 needs to be based on epoxy because of its amazing and incredibly high shear strength. The rocket needs to carry satellites to the space and that means that the rocket will be going through troposphere all the way up to exosphere and beyond. This also means that the rocket will undergo extreme pressure, temperature, and stress, which makes it impossible to use super glue in this case.
Suggestive Solution
Using epoxy seems a fair and reliable solution because the shear strength is high and it can handle the stress that the rocket would go through all the layers of the atmosphere until it reaches the right spot in the space.
After reaching the destination, the rocket also needs to deploy the satellites, which again needs a high shear strength, which we can expect from epoxy.
- Lightweight UAV Frame Assembly
Problem Identification
For understanding deeply about the super glues, let’s take an example of 3D printed drone chassis. When they printed the drone chassis, they needed to attach the mechanism with it. In order to achieve this goal, rivets are the most common fastening tools used. However, rivets also add weight to the drone and reduce the battery efficiency.
Suggestive Solution
So a better way was to use super glue instead of rivets. A drastic reduction of up to 15% weight could be noticed in this case.
Super glue proved to be a solid solution because of its lightweight nature and a quick and strong fixture to the internal components. The mechanism was to be placed inside the chassis, which gave the super glue protection against the external environment. While lightweight rivets are a conceptual solution, it is still far from reality when comparing its weight against super glue fixtures. So in this case, super glue becomes a lightweight bonding for drones.
FAQs
Can super glue replace epoxy in aircraft repairs?
No, there is no way that among every possible thermal cycling adhesive aerospace, a super glue can replace epoxy when repairing the aircrafts and is not even advisable to experiment either. The reason behind a big no is that the bond strength of a super glue is very low as compared to epoxy when they are fully cured. And assuming the immense pressure, weather conditions, and operation of aircrafts, using a super glue will break down the repaired area mid air.
How to prevent epoxy brittleness at cryogenic temps?
When a material breaks down or has fractures in it, we call it brittleness, which is common in epoxy is we don’t apply it properly. Epoxy can also brittle at cryogenic temperatures, that calls for a need for expert engineering solution.
We can add flexible toughening agents or materials rubber or silicone, or use silica or carbon nanotubes to improve the overall strength of epoxy after it cures. If we mix a little bit of thermoplastics in the epoxy mixture, we can get resistance to cracks in the solution after it cures.
An expert tip: Use CTBN-modified epoxy (e.g., 3M DP460NS)
Conclusion
It’s clear that the super glue vs epoxy are two totally different compounds that we can use in aircraft repair at different places. While epoxy is much versatile than super glue, it doesn’t mean that the super glue is not worth it. If your project is in the aerospace industry and you are looking for some cost-effective epoxy procurement, you need someone who is an expert in this field, someone who can give you the right guidance and among such companies is Jiujutech.
With more than 10 years of industrial experience, Jiujutech will help you with the right epoxy and additives that will give a fantastic solution to aircraft manufacturing and repairs. If you need a high shear strength adhesive for composites, they will suggest the best epoxy and if you need lightweight bonding for drones or internal components, then they will suggest the most appropriate super glue.
