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Measuring Interface Strength in Single Fiber Composites: The Effect of Stress Concentrations

Published

Author(s)

Gale A. Holmes, R C. Peterson

Abstract

Fiber-matrix interface strength is known to be a critical factor in controlling the long-term performance of structural composites. This parameter is often obtained by using the average fragment length data generated from the single-fiber fragmentation test (SFFT). The interfacial shear strength is then obtained by using this data in a micro-mechanics model that describes the shear-stress transfer process between the matrix and the fiber. Recently, a non-linear viscoelastic micro-mechanics model was developed to more accurately account for the matrix material properties. This new model indicates that the interface strength is dependent on the testing rate. Experimentally, it has been shown that the final fragment length distribution in some systems is dependent on the testing rate. However, data analysis using the new model indicates that the distribution change with testing rate is promoted by the presence of high stress concentrations at the end of the fiber fragments. From the model, these stress concentrations were found to exist at very low strain values. Experimentally, the fragment distributions obtained from specimens tested by different testing rates were found to be significantly different at strain values well below the strain values required to complete the test. These results are consistent with the research of Jahankhani and Galiotis and finite element calculations performed by Carrara and McGarry. These authors concluded that stress concentrations can promote failure of the fiber-matrix interface on the molecular level. Our results support this conclusion. In addition, our research results suggest that altering the SFFT testing rate can lower the magnitude of these stress concentrations and minimize failure of the fiber-matrix interface.
Proceedings Title
Interfaces, Adhesion and Processing in Polymer Systems
Volume
629
Conference Dates
April 24-27, 2000
Conference Location
Undefined
Conference Title
Materials Research Society Symposium Proceedings

Keywords

interfacial shear strength, model, non-linear viscoelasticity, single fiber fragmentation test, stress concentration

Citation

Holmes, G. and Peterson, R. (2000), Measuring Interface Strength in Single Fiber Composites: The Effect of Stress Concentrations, Interfaces, Adhesion and Processing in Polymer Systems, Undefined, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851781 (Accessed April 23, 2024)
Created June 30, 2000, Updated October 12, 2021