Impact damage in graphite/epoxy laminates: Damage characterization, acoustic emission, and finite element simulation

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:6109643

Ghaffari, S

This thesis is concerned with the characterization and detection of impact damage in graphite/epoxy quasi-isotropic composite laminates. Particular emphasis is placed on non-visual impact damage. It is well-established that such damage can cause a significant degradation in performance. Therefore, both experimental and analytical investigations were conducted, addressing some of the more critical issues related to the general subject of impact damage in composite laminates. In the experimental phase the impact-damaged zone was fully characterized employing a variety of nondestructive and destructive testing techniques. The effect of the damage on degradation in mechanical performance is discussed. Primary emphasis in this research was given to the acoustic emission technique. During the course of this research it has been determined that a significant amount of emission is generated by the grating among existing fracture surfaces. Therefore, emphasis was placed on analyzing and identifying this friction emission. In the analytical phase, two major issues were addressed. First, the state-of-damage during the impact event has been predicted using a numerical simulation procedure. A dynamic finite element stress analysis was performed from which the stress distributions across the laminate thickness were calculated for cross-ply and quasi-isotropic laminates. Second, the initiation and progression of matrix damage (i.e., matrix splitting and delamination) in model specimens have been investigated employing a numerical simulation procedure. Strain energy release rates (for Mode-I and Mode-II fracture) were calculated using a finite element stress analysis and employing the crack closure technique.

• Research Organization: Drexel Univ., Philadelphia, PA (USA)
• OSTI ID: 6109643
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
ACOUSTIC EMISSION TESTING
ACOUSTIC TESTING
CARBON
COMPOSITE MATERIALS
DAMAGE
DESTRUCTIVE TESTING
ELEMENTAL MINERALS
ELEMENTS
EPOXIDES
FAILURES
FINITE ELEMENT METHOD
GRAPHITE
IMPACT STRENGTH
IMPACT TESTS
MATERIALS
MATERIALS TESTING
MECHANICAL PROPERTIES
MECHANICAL TESTS
MINERALS
NONDESTRUCTIVE TESTING
NONMETALS
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PERFORMANCE
SIMULATION
STRESS ANALYSIS
TESTING