Effect of reinforcement and fiber-matrix interface on dynamic fracture of fiber-reinforced composite materials

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7267845

Khanna, S K

The experimental technique of dynamic photoelasticity coupled with high speed photography has been used to study the interaction of running cracks with brittle and ductile fibers embedded in a brittle polymeric matrix. The effect of reinforcement and the fiber-matrix interface on dynamic stress intensity factor, crack bridging phenomena, crack surface morphology and toughening mechanisms occurring during dynamic fracturing of reinforced brittle matrix composites has been investigated. It is found that reinforcement reduces the crack velocity and the stress intensity factor. Thus the energy supplied to the crack tip is reduced resulting in reduction of the crack jump distance. Fiber pullout experiments were done to characterize the fiber-matrix interface. Rapid pullout results in an increase in interface shear strength. For rapid pullout of fibers the difference between maximum pullout loads. for well and weakly bonded fibers, is much smaller than for very slow pullout. A fiber-matrix interface which is weaker in the vicinity of the crack path, termed the partly debonded interface, produces higher crack closing forces and lower stress intensity factor compared to well bonded fibers. The former interface condition results in low fracture energy and shorter crack jump compared to the later. The interface condition significantly affects the fracture surface morphology. The fracture surface roughness is lower for reinforced materials compared to monolithic. Further the partly debonded fibers result in lower surface roughness compared to the well bonded fibers. Inclined fibers with various interface conditions have no significant effect on the stress intensity factor. The fiber debonded length, however, decreases, as compared to fibers which are aligned with the loading direction, due to the kinking of the fibers.

• Research Organization: Rhode Island Univ., Kingston, RI (United States)
• OSTI ID: 7267845
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
COMPOSITE MATERIALS
CRACK PROPAGATION
FRACTURE MECHANICS
FRACTURE PROPERTIES
MATERIALS
MECHANICAL PROPERTIES
MECHANICS
REINFORCED MATERIALS