Date Approved

6-15-2021

Embargo Period

6-17-2021

Document Type

Thesis

Degree Name

M.S. Mechanical Engineering

Department

Mechanical Engineering

College

Henry M. Rowan College of Engineering

Advisor

Behrad Koohbor, Ph.D.

Committee Member 1

Francis M. Haas, Ph.D.

Committee Member 2

Anu Osta, Ph.D.

Keywords

Composite, Debonding, Digital Image Correlation, Finite Element Analysis, Full-Field Measurement, In Situ

Subject(s)

Composite materials--Bonding; Failure analysis (Engineering)

Disciplines

Mechanical Engineering

Abstract

Macroscopic mechanical and failure properties of fiber-reinforced composites depend strongly on the properties of the fiber-matrix interface. For example, transverse cracking behavior and interlaminar shear strength of composites can be highly sensitive to the characteristics of the fiber-matrix interface. Despite its importance, experimental characterization of the mechanical behavior of the fiber-matrix interface under normal loading conditions has been limited. This work reports an experimental approach that uses in situ full-field digital image correlation (DIC) to quantify the mechanical and failure behaviors at the fiber-matrix interface. Single fiber model composite samples are fabricated from a proprietary epoxy embedding a single glass rod (macro fiber). These samples are then tested under transverse tension. DIC is used to measure the deformation and strain fields in the glass rod, epoxy, and their interface vicinity. Initiation and propagation of the fiber/matrix debond are discussed. A similar approach is applied on samples that encompass two glass rods with the objective to explore the specific patterns of debonding at the fiber/matrix interface in terms of relative fiber spacing and orientation. Experimental results are complemented by finite element analyses. The findings of this research indicate that the inter-fiber distance and angle play major roles in the interface debond nucleation and propagation as well as matrix failure response in unidirectional composites subjected to transverse tension.

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