Abstract
Delamination is a commonly observed failure mode in continuous fibre-reinforced composite
laminates subjected to static or fatigue tensile loading. Its initiation is often triggered by matrix
cracks, i.e. cracks in the resin running parallel to the fibres in the off-axis ply of the laminate, which
result in high interlaminar stresses at the ply interface. In the present paper, local delaminations
growing uniformly from the tips of matrix cracks in the inner φ -layer of a general symmetric
s [(S)/φ] laminate subjected to in-plane tensile loading are analysed. The strain energy release rates
associated with such delaminations are predicted analytically using the Equivalent Constraint Model
of the damaged laminate. Stress field in the damaged ply is determined from the analysis of a
representative segment containing one crack and two crack tip delaminations by means of a 2-D shear
lag method. Closed-form expressions for ld GI (Mode I contribution), ld GII (Mode II contribution) and
the total ld G strain energy release rates are derived, representing them as linear functions of the first
partial derivatives of the degraded stiffness properties of the damaged φ -layer with respect to the
delamination area. The expressions give strain energy release rates that depend both on the matrix
crack density and delamination area. Their dependence on the matrix crack density, delamination area
and ply orientation angle is examined both for balanced and unbalanced laminates. Comparison with
the closed-form expression suggested by O’Brien is also made
laminates subjected to static or fatigue tensile loading. Its initiation is often triggered by matrix
cracks, i.e. cracks in the resin running parallel to the fibres in the off-axis ply of the laminate, which
result in high interlaminar stresses at the ply interface. In the present paper, local delaminations
growing uniformly from the tips of matrix cracks in the inner φ -layer of a general symmetric
s [(S)/φ] laminate subjected to in-plane tensile loading are analysed. The strain energy release rates
associated with such delaminations are predicted analytically using the Equivalent Constraint Model
of the damaged laminate. Stress field in the damaged ply is determined from the analysis of a
representative segment containing one crack and two crack tip delaminations by means of a 2-D shear
lag method. Closed-form expressions for ld GI (Mode I contribution), ld GII (Mode II contribution) and
the total ld G strain energy release rates are derived, representing them as linear functions of the first
partial derivatives of the degraded stiffness properties of the damaged φ -layer with respect to the
delamination area. The expressions give strain energy release rates that depend both on the matrix
crack density and delamination area. Their dependence on the matrix crack density, delamination area
and ply orientation angle is examined both for balanced and unbalanced laminates. Comparison with
the closed-form expression suggested by O’Brien is also made
| Original language | English |
|---|---|
| Title of host publication | Proceedings of the 2003 International Conference on Composite Materials |
| Subtitle of host publication | San Diego, CA, USA, July 14-18 2003 |
| Publisher | ICCM |
| Number of pages | 10 |
| Publication status | Published - 2003 |
| Event | 14th International Conference on Composite Materials - San Diego, United States Duration: 14 Jul 2003 → 18 Jul 2003 http://www.iccm-central.org/Proceedings/ICCM14proceedings/index.htm |
Conference
| Conference | 14th International Conference on Composite Materials |
|---|---|
| Abbreviated title | ICCM-14 |
| Country/Territory | United States |
| City | San Diego |
| Period | 14/07/03 → 18/07/03 |
| Internet address |
Keywords
- delamination
- matrix cracking
- strain energy release rate