Circumventing boundary effects while characterizing epoxy/copper interphases using nanoindentation. Issue 9 (22nd November 2017)

• Record Type: Journal Article
• Authors: Elabshihy, Karim; Kalinka, Gerhard
• Is Part Of: Composite interfaces. Volume 24:Issue 9(2017)
• Page Start: 833
• Page End: 848
• Publication Date: 2017-11-22
• Subjects: Interphase -- polymer-metal -- epoxy -- copper -- composites -- nanoindentation; Composite materials -- Periodicals; 620.11805
• DOI: 10.1080/09276440.2017.1286878
• Languages: English
• ISSNs: 0927-6440

Abstract

Abstract: Characterization of the size and mechanical properties of interphases is essential when designing multicomponent materials. When nanoindentation is used to investigate the size and mechanical properties of an interphase, a common challenge is that the indenter or the stress zone formed around it are often restricted by the reinforcement, making it difficult to distinguish the mechanical property variations caused by the interphase itself from those caused by the boundary effect. In this work, a testing system was developed that allows determining the indent affected zone and accounting for it in the interphase measurements of an epoxy/Cu system. Using finite element analysis, we confirmed the validity of the proposed system. Nanoindentation was used to investigate the interphase between copper and two different epoxy systems; amine-cured and anhydride-cured. Nanoindentation results showed that a copper layer that is only 10 nm thick still exhibits a constriction effect on the indentations in its vicinity. The amine-cured epoxy did not show any sign of interphase existence using the introduced method. However, a soft interphase with a thickness of ~1.7 μm was measured on the anhydride-cured epoxy. Furthermore, we show that the proposed system can be used to determine the interphase thickness as well as its relative mechanical properties regardless of the indentation depth. This system can be further used for investigating other polymer/metal interphases to better understand the factors influencing them, thus helping engineer the interphase size and properties to enhance composite performance.