Optimization of interfacial bonding at metal case-adhesive and adhesive-EPDM insulation interfaces through surface treatments for rocket motor applications

Date

2026-1-22

Author

Kahraman, Nehir

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Elastomer-metal bonding systems are critical in the defense and aerospace industry because they operate under high mechanical loads and challenging environmental conditions. Creating a reliable bond is critical for maintaining structural integrity and ensuring service safety. Although these bonding systems are commonly utilized in insulation applications, bonding EPDM with adhesives poses serious challenges due to its low surface energy and complex surface chemistry. Existing literature focuses primarily on vulcanization-based or primer-assisted approaches; however, the quantitative effect of surface cleanliness on adhesive-based EPDM-metal bonding has not been sufficiently addressed. In this study, the adhesion behavior of EPDM rubber bonded to steel substrates using epoxy-based structural adhesives was investigated. The research evaluates the effects of surface roughness, surface cleanliness, mechanical roughening methods of EPDM, and atmospheric plasma application. The metal-adhesive interface was isolated through metal-to-metal bonding experiments, while the EPDM-adhesive interface was enhanced by mechanical roughening and plasma treatments. Adhesion performance was evaluated through tensile and shear tests, followed by failure mode analysis. The results indicated that the primary interface limiting bond strength was the EPDM-adhesive interface, not the metal-to-adhesive interface. Metal-to-metal experiments showed that optimum surface conditions correspond to Ra 4–8 µm and 0–50 RFU cleanliness. Mechanical roughening of EPDM surfaces resulted in bond strength increases of up to 154%, while atmospheric plasma application provided an additional strength increase of up to 54%, especially under shear loads. This study presents a quantitative and systematic surface preparation approach focusing on the EPDM interface for optimizing EPDM-metal bonding systems.

Subject Keywords

Adhesive bonding, Elastomer–metal bonding, Interface optimization, Surface cleanliness, Surface roughness

URI

https://hdl.handle.net/11511/118722

Collections

Graduate School of Natural and Applied Sciences, Thesis