A Preliminary Investigation of Dual Mode Fracture Sustained by Graphite/Epoxy Laminates Impacted by High-Velocity Spherical Metallic Projectiles

Abstract

This thesis studies the basis for delamination initiation and propagation within an impacted laminate. The work provides an explanation for fracture mode transformation along the projectile's path. Post-impact observations of graphite/epoxy (AS4/3501-6) laminates penetrated by steel spheres (0.5-inch diameter) reveal a fracture mode, similar to shear plugging, adjacent to the impacted surface. This fracture mode is contrasted with that of delamination adjacent to the rear surface. The sudden transition from shear plugging to delamination occurs when the projectile interacts with the returning impact-generated tensile wave. To demonstrate the transition, results are presented from ballistically impacted laminates containing a series of embedded carbon stress and constantan strain gages. Results are based on impact velocities of 1825 and 2380 f/s. Transverse stress waves are shown capable of creating delamination until attenuated by a localized compression front associated with the on-coming projectile.

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Document Details

Document Type
Technical Report
Publication Date
Apr 01, 1992
Accession Number
ADA255790

Entities

People

  • Gregory J. Czarnecki

Organizations

  • Wright Laboratory

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies
  • Weapons Technologies

DTIC Thesaurus Topics

  • Composite Materials
  • Data Acquisition
  • Delamination
  • Dynamic Tests
  • Elastic Waves
  • Failure Mode And Effect Analysis
  • Graphitic Materials
  • Impact Tests
  • Laminates
  • Materials Laboratories
  • Materials Testing
  • Mechanical Properties
  • Mechanics
  • Stress Waves
  • Tensile Stress
  • Test Methods
  • Wave Propagation

Readers

  • Combustion Dynamics and Shock Wave Physics.
  • Structural Health Monitoring of Composite Structures.
  • ballistics.