A Simple Methodology for Observing Mechanical Properties of Nanocomposites. Part 2: Investigation of Interfacial Properties in E-Glass Fiber Model Composites

Published

February 20, 2004

Author(s)

Jae Hyun Kim, Gale A. Holmes, Chad R. Snyder

Abstract

The fiber/matrix interfacial shear strength (IFSS) and the fiber/matrix interphase fracture toughness are critical parameters that control failure initiation and crack propagation in composites. In spite of this importance, most IFSS test methods ignore these parameters. As a result, output results from IFSS tests cannot be used as input parameters for modeling the failure behavior of real or model composites. are not used to quantify the failure behavior of real fiber interaction, and this ignorance cause the difference between the measured values determined by single fiber-model composites (i.e. fragmentation test) and multi fiber-real composites (i.e. direct shear and short beam test).For this reasons, we have sought to obtain in situ IFSS parameters through the testing of micro-composites that consist of 2-D and 3-D multi-fibers arrays, whose inter-fiber spacing is comparable to the spacing observed in typical composites. This testing methodology admits the direct observation how IFSS, inter-fiber spacing, deformation rate, and matrix cracks influence fiber break clustering, critical flaw nucleation, and the in situ IFSS. The in situ IFSS obtained from this testing approach provides an experimental link to the ineffective length parameter that is used in statistics based micromechanics models. These models seek to quantify the strength and failure behavior of unidirectional laminae, the basic building block of composite structures, using micromechanics input parameters. The key goal of this research is to develop a predictive composite failure model by linking micromechanics parameters that quantify the local properties that control failure initiation and crack propagation in a composite lamina to computationally efficient failure criteria.Using this measurement technique, the IFSS of single fiber and 2-D multi fiber composites having 15?m interfiber distance were measured using testing conditions where the interval between successive deformations was 10 min or 1h. The experimental results showed that the average IFSS of the cluster fibers measured with the 10 min time interval is lower than those tested using the 1 h time interval. Moreover, the IFSS obtained from a single fiber was found to be lower than the in situ IFSS that is obtained from the 2-D multi-fiber micro-composite. It was concluded that the reduction in IFSS is due to the interaction between the closely spaced fibers and the clustering of fiber breaks that occurs in the adjacent fibers that surround the fiber that contains the initial break.

Proceedings Title

Sigma Xi Postdoctoral Poster Presentations, 2004

Conference Dates

February 19-20, 2004

Conference Location

Gaithersburg, MD

Pub Type

Conferences

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Keywords

epoxy clay, methodology, nanocomposite

Citation

, J. , Holmes, G. and Snyder, C. (2004), A Simple Methodology for Observing Mechanical Properties of Nanocomposites. Part 2: Investigation of Interfacial Properties in E-Glass Fiber Model Composites, Sigma Xi Postdoctoral Poster Presentations, 2004, Gaithersburg, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=852326 (Accessed April 24, 2024)