Static Debonding Initiation Stress of Fiber Glass Composite

Abstract

Mesoscale debonding initiation stress of a bundle of glass fibers and epoxy matrix under static loading is investigated. A special cylindrical bar specimen was designed for the experiment. The specimen contains a bundle of glass fibers in the center and the bundle diameters were 1 and 2mm. The fiber diameter is 7µm. A static tension test was performed under the displacement control. The applied load-displacement curve was recorded for each specimen and then the debonding initiation load was defined as the deviation point from the linear curve. In addition, the debonding length was measured directly from the tested specimen. Using the debonding load measured from experiment, an axisymmetric finite element analysis is performed and debonding parameters K₁ and K₂ were computed. The results show the debonding initiation is fully dominated by an opening mode rather than a sliding mode and the stress intensity factor K₁ for the debonding initiation is 2.0E+05Pa√m. The mixed mode fracture takes place in the debonding propagation with constant mode mixity around 41.0 degree and the averaged stress intensity factors are 1.67E+05Pa√m and 1.41E+05Pa√m for the opening and the sliding mode, respectively.