Composite Materials Lab at SU
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Current research projects in composites

Current research projects being performed at the SU-CML include:

Characterization and Prediction of Delamination Growth in Laminated Composites

This project focuses on the following three tasks:

  1. Investigation of mode III delamination growth
    It has recently been shown that mode III delamination advance in laminated polymeric composites generally consists of a complex pattern of evolving damage, and is quite different from that which has historically been assumed to occur. This observation has been used to explain the inability of current mode III delamination toughness tests to obtain a mode III toughness that was independent of specimen and test geometry. This research task focuses on
    • understanding the nature of mode III growth in laminated polymeric composites,
    • choosing the appropriate parameter(s) to characterize this mode of growth and choosing or developing the associated test method(s), and
    • development of a methodology to predict mode III growth in practical structural geometries.
    This research task is being conducted in collaboration with NASA Langley Research Center.
  2. Determination of delamination failure surfaces
    This task involves the determination of the mode I, mode II, mode III and mixed-mode delamination toughness of laminated composites. Current sub-tasks include:
    • Development of an ASTM standardized end-notched flexure test for the determination of mode II toughness, GIIc
    • Development of a new mode III test for the determination of mode III toughness, GIIIc, as described in task 1.
    • Development of a new test to determine toughness for various mode mixities involving mode III and mode I and/or mode II loadings.
  3. Determination of mode decomposition
    For laminated graphite/epoxy composites, it has been shown that a singular field-based mode mix decomposition is generally not valid for the prediction of delamination growth. Conversely, it has been shown that a non-classical definition, using a crack tip element-based decomposition, shows excellent predictive capability (Davidson, et al: Comp Sci Tech, 66(10), 2006, 1479-1496; Int J Fracture, 105(4), 2000, 343-365; ASTM STP 1242, 1997, 109-128). This task involves extending this research to be more generally applicable to practical structural geometries.

Damage Tolerance of PMCs with Application to Air and Space Vehicles

The overarching objective of this project is to advance the state-of-the-art of damage tolerant design of polymer matrix composites (PMCs). Current work focuses on the growth of (1) interlaminar delaminations under general mixed-mode I-II-III loadings, and (2) barely visibly impact damage in honeycomb sandwich laminates subjected to bending and/or compression loads. Specific research tasks involve using a combination of experimental, analytical and numerical methods to examine, understand and predict the growth of these types of damages and their criticality for representative hygrothermomechanical loadings. Expected outcomes are predictive models, supporting experimental methods for model characterization, realistic acceptance/rejection criteria, and "rules-of-thumb" for damage-tolerant design that can readily be incorporated into practical engineering environments.

Barry D. Davidson,