Burst Tests of Filament-Wound Graphite-Epoxy Tubes: Pathfinder Test Series for Delta II GEM Motor Cases

Abstract

A test program was conducted to investigate the failure modes of undamaged and damaged graphite-epoxy cylindrical tubes subject to internal pressure, and to simulate the failure mode of the Delta graphite epoxy motor (GEM) case K404. There were two phases of this test program: the mini-test series and the pathfinder series. The mini-test series, using 1.5-in. diameter tubes, included five tests. The pathfinder series, using 4.00-in. diameter tubes, included 41 tests. Two types of intentional damage were made to some of the tubes: either a longitudinal-line cut or a single-point impact. A Kodak High Speed Motion Analyzer model 4540 was used to record images of the fracture process. Testing was conducted under three conditions: hydraulic pressurization, pneumatic pressurization with solid inserts, and pneumatic pressurization with inert propellant inserts. Several failure modes were observed. A tube with a longitudinal cut can fail in three different modes: a local leakage mode, a bursting mode with a fracture initiating from the cut, or a bursting mode with complete tube disintegration. In testing of impact-damaged tubes, the results show that the burst pressure decreases with increasing impact load. At an impact load of 335 Ib, the burst pressure decreases by 33% compared to the undamaged condition. The failure initiation point of the impact-damaged tubes was not necessarily at the impact location. Apparently, impact can cause localized damage to other areas of tubes. However, thermography and ultrasound inspections failed to detect this damage. This is possibly because these nondestructive examination (NDE) techniques can detect delamination but not fiber breakage in composite materials.

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Document Details

Document Type
Technical Report
Publication Date
Dec 20, 2000
Accession Number
ADA390656

Entities

People

  • D. J. Chang
  • P. R. Valenzuela
  • T. V. Albright

Organizations

  • The Aerospace Corporation

Tags

Communities of Interest

  • Energy and Power Technologies
  • Space
  • Weapons Technologies

DTIC Thesaurus Topics

  • Bending Stress
  • Cameras
  • Composite Materials
  • Data Acquisition
  • Failure Mode And Effect Analysis
  • Graphitic Materials
  • Impact Loads
  • Materials
  • Materials Laboratories
  • Materials Processing
  • Materials Testing
  • Mechanical Properties
  • Mechanics
  • Photographs
  • Pressurization
  • Propellants
  • Tensile Strength

Readers

  • Rocket Propulsion.
  • Structural Health Monitoring of Composite Structures.
  • ballistics.