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Determination of Interfacial Shear Strength in Epoxy/Glass Composites by Multi-Fiber Fragmentation Test (MFFT)



Edward D. McCarthy, Jae H. Kim, N. Alan Heckert, Stefan D. Leigh, Gale A. Holmes, Jeffrey W. Gilman


The mechanical strength of a structural composite is strongly affected by the strength and toughness of the interface achieved between the continuous matrix phase, or resin, and the re-inforcing phase, normally consisting of multiple arrays of carbon or glass fibers. Interfacial shear strength (IFSS) is the accepted parameter for quantifying the strength of the matrix-fiber interface. However, the value of IFSS is not directly accessible by measurement and must be approximated indirectly from other data. One mechanical test which generates such data is the single fiber fragmentation test (SFFT). In SFFT, a taut single fiber is embedded in a thermoset resin. Once fabricated, the composite specimen is strained under tensile conditions in timed increments. During this strain process, breaks appear in the fiber to relieve stress on the composite. As the test progresses, more breaks appear in the fiber until a time is reached where no further breaks appear. This point represents the stress saturation of the fiber. Further deformation on the specimen after this point results in no additional breaks. By recording the overall strain and load on the fiber at saturation, as well as the number of breaks and break fragment lengths, an approximate calculation for the interfacial shear strength may be made using an elementary mechanical force balance. In this paper we extend the SFFT technique to multiple fiber arrays (multi fiber fragmentation test MFFT) to more closely study the effect of fiber-fiber interactions on stress transfer, and simplifying assumptions about the matrix. We use MFFT data obtained from a conventional epoxy / E-glass system to show that the spatial distribution of fiber breaks along the axes of fibers in close bundles is fitted best by a uniform rather than a Weibull distribution.
Proceedings Title
Conference Dates
July 28, 2013-August 2, 2014
Conference Location
Montreal, CA


composites, interface, interfacial shear strength, E-glass, epoxy-resins


McCarthy, E. , Kim, J. , Heckert, N. , Leigh, S. , Holmes, G. and Gilman, J. (2013), Determination of Interfacial Shear Strength in Epoxy/Glass Composites by Multi-Fiber Fragmentation Test (MFFT), THE 19TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS (ICCM) MONTREAL, Montreal, CA (Accessed July 23, 2024)


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Created August 1, 2013, Updated October 12, 2021