Accession Number : ADA255790


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


Descriptive Note : Final rept. 1 Jan 1990-15 Dec 1991


Corporate Author : WRIGHT LAB WRIGHT-PATTERSON AFB OH


Personal Author(s) : Czarnecki, Gregory J


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a255790.pdf


Report Date : Apr 1992


Pagination or Media Count : 164


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.


Descriptors :   *LAMINATES , *IMPACT STRENGTH , *DELAMINATION , *IMPACT LOADS , *GRAPHITE EPOXY COMPOSITES , VELOCITY , DIAMETERS , PATHS , SPHERES , SURFACES , FLEXURAL STRENGTH , TRANSITIONS , STRESS WAVES , TRANSFORMATIONS , STRAIN GAGES , PENETRATION , FRACTURE(MECHANICS) , STEEL , THESES , PROJECTILES , STRESS ANALYSIS


Subject Categories : Laminates and Composite Materials
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE