Abstract
The growth of delaminations in polymer-matrix fibre composites under cyclic-fatigue loading in operational aircraft structures has always been a very important factor which has the potential to significantly affect the service-life of such structures. The recent introduction by the FAA of a 'slow growth' approach to the certification of composites has further focused attention on the experimental data and the analytical tools needed to assess the growth of delaminations under fatigue loads. Therefore, a main emphasis of the present paper is to address the topic of the growth of delaminations in polymer-matrix fibre composites under cyclic-fatigue loading using a fracture-mechanics approach. Specific attention is given to the test and data-reduction procedures that are required in order to determine a 'valid' rate of crack growth, da/dN, versus the range of the energy release-rate, ΔG (or the maximum strain-energy release-rate, Gmax, in a cycle), relationship. Only such 'valid' relationships can be reliably used (a) to characterise and compare different types of composites and (b) for lifing the in-service composite structures. The important role played by fibre-bridging that may occur behind the tip of the advancing delamination, and which causes retardation of the fatigue crack growth rate, is highlighted. Finally, it is shown that such retardation effects cannot usually be avoided when using the Mode I double-cantilever beam test to ascertain experimentally the fatigue behaviour of composites, so that a means of estimating a 'valid' (low retardation) relationship is needed. The present chapter presents one such approach that is based on the use of the Hartman-Schijve delamination growth equation.
Original language | English |
---|---|
Title of host publication | Aircraft Sustainment and Repair |
Editors | Rhys Jones, Alan Baker, Neil Matthews, Victor Champagne |
Place of Publication | Oxford UK |
Publisher | Elsevier |
Chapter | 13 |
Pages | 763-797 |
Number of pages | 35 |
Edition | 1st |
ISBN (Electronic) | 9780081005446 |
ISBN (Print) | 9780081005408 |
DOIs | |
Publication status | Published - 2018 |
Keywords
- Delamination growth
- Fatigue threshold
- Impact damage
- Lead delaminations
- Scatter