Bonding with epoxy:
Loading scenario: Ensure a sufficient adhesive is selected for the loading scenario. For example, 3M DP420 has an estimated shear strength of ~2,200 /sq. in. with common materials like aluminum and steel. When bonding to unique materials, such as HDPE, other adhesives may be better suited.
Proper fit: A bond-gap of ~0.005”-0.010” (per side) is recommended. This will ensure the proper amount of adhesive is used. Other adhesives may require a thinner, or thicker, bond gap. Consult the adhesive supplier for proper fit recommendations.
Bond Length: For ferrule tubing***, a good rule of thumb is a minimum bond length of 2-3x the inside diameter. For tubes <1” diameter, we recommend a 3” bond length as a default.
***our tubing is not ferrule tubing, I don't think
Galvanic Corrosion: Carbon fiber can cause galvanic corrosion on aluminum. If the aluminum is anodized, this should prevent corrosion since there is a layer of oxide between the carbon fiber and bare aluminum. The epoxy adhesive also can act as a layer to prevent corrosion. Another common way of preventing galvanic corrosion is to use a non-conductive outer (or inner) layer of fiberglass in the carbon fiber part to ensure the aluminum and carbon fiber do not come in contact.
For gluing the carbon fiber and aluminium, the 3M SCOTCH-WELD constructional glues are recommended. These are epoxy-type glues: (https://exelcomposites.com/guide-to-composites/fabrication-methods/gluing-of-carbon-fiber-composite-to-aluminum/)
| Type 1 | 9323 | Red, very high thermal performance, high strength properties also in 80 ºC (23,4 N/mm2), especially for Al-gluing, the hardest of the three. |
| Type 2 | 7838 | Yellow, high thermal performance, high strength properties, more elastic type glue |
| Type 3 | 2216 | Grey, the most elastic glue type |
Bond prep
Abrade: Using 120 grit sandpaper, or one of the other methods mentioned above, remove all gloss from the bond areas. This will increase the surface energy, thus increasing the strength of the bond.
Clean Surface: Wipe bond area with solvent. Gloves should be worn during all steps, so oils are not transferred to the bonding area. Allow solvent to evaporate (surface should look dull, gloss should to be removed). Can do a water bead test to verify sanding is adequate.
Bond: Apply adhesive liberally throughout both bond surfaces. 100% coverage will ensure a proper bond. When connecting the parts, adequate adhesive squeeze out should be observed.
Clean-up: After application, wipe away all excess epoxy. Use solvent to clean the non-bonded surface.
Fixture: Fixture or secure the bonded assembly to prevent movement while parts cure. As the epoxy cures, there is a possibility the bonded components will shift, affecting dimensions of the assembly.
Cure: Refer to the adhesive tech data sheet for the correct time, temp, and sometimes humidity cure process. Some epoxies require multiple days at room temp to cure properly. Do not handle the part until fully cured.
Information from: https://www.clearwatercomposites.com/resources/how-to-guides/bond-carbon-fiber-tubes/
Old information:
Noninvasive Connections:
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