A Predictive Methodology for Delamination Growth in Laminated Composites Part II: Analysis, Applications, and Accuracy Assessment

Details

• Creators:
  Davidson, B. D.
• Corporate Creators:
  Syracuse University. Department of Mechanical, Aerospace and Manufacturing Engineering
• Corporate Contributors:
  United States. Department of Transportation. Federal Aviation Administration. Office of Aviation Research
• Subject/TRT Terms:
  • Airplanes
  • Composite materials
  • Laminates
  • Finite element method
  • Fracture mechanics
  • Crack propagation
• Publication/ Report Number:
  DOT/FAA/AR-01/56
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Edition:
  Final Report
• Corporate Publisher:
  United States. Department of Transportation. Federal Aviation Administration. William J. Hughes Technical Center
• Description:
  A nonclassical, energy release rate-based approach to predict delamination growth is described that overcomes the limitations of current, state-of-the art methodologies. First, two- and three-dimensional crack-tip elements are introduced. When a classical, singular field-based mode decomposition procedure is used, the crack-tip elements are shown to predict the same values of energy release rate and mode mixity as two- and three-dimensional continuum finite element analyses for a wide variety of geometries, materials, lay-ups and loadings, including stiffened-skin construction typical to that used in aircraft construction. However, the crack tip element (CTE) analyses are considerably simpler and require orders of magnitude less development and execution time. Next, it is demonstrated that the CTE analyses may also be used to decompose the total energy release rate into nonclassical mode I, II, and III components. This nonsingular field (NSF) decomposition may be used, along with toughness versus mode mix data obtained from unidirectional laminates with midplane delaminations, to predict delamination growth with considerably better accuracy than the classical, state-of-the-art approach. This is due to the fact that the near-tip damage zone is sufficiently large in polymeric matrix composites to invalidate the classical assumptions, whereas the NSF mode decomposition is constructed in a manner that is insensitive to the details of this local damage state. This is demonstrated by applying both the classical and CTE/NSF approaches to make delamination growth predictions in four different graphite-reinforced composites, with matrices that include an epoxy, a toughened epoxy, a thermoplastic interlayer toughened epoxy, and a thermoplastic. For this portion of the study, only flat plate geometries were considered. However, these included a wide variety of in-plane and bending loading conditions applied to unidirectional and multidirectional laminates containing delaminations at arbitrary locations. For all materials, loadings, and lay-ups examined, the CTE/NSF approach is demonstrated to have excellent predictive ability, whereas, in many cases, the predictive capability of the classical approach is quite poor. Finally, the CTE/NSF approach is used to predict delamination growth in a stiffened-skin structural geometry under two different types of loadings and excellent comparisons with experimental results are obtained. It is believed that the combination of computational simplicity and predictive accuracy makes the CTE/NSF approach an attractive, effective delamination growth assessment tool that may readily be implemented into current engineering environments.
• Format:
  PDF
• Funding:
  94-G-022
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/94059/dot_94059_DS1.pdf
• File Type:
  [PDF - 3.56 MB]
• Collection(s):
  FAA William J. Hughes Technical Center for Advanced Aerospace
• Main Document Checksum:
  urn:sha-512:9fb608491e291e0d414a2ba19d1e22d6e728bff67c85ecf6136570cd1cddcaf8ca203a157311e27475ecb66871f3d63325c8d3b0e14e0a33468d050f6f5b2ed5