Crack Paths 2009

analysed. Moreover the effectiveness of the optical microscopy technique to analyse the

damage evolution was investigated.

The main conclusions are as follows:

In terms of stress-life data, the influence of stacking sequence and ply orientation at

the interface is limited. even in comparison with previous data on all 0° adherend

joints. Fillet corner geometry and a longer overlap result instead in improved fatigue

strength.

Damage evolution is characterised by a nucleation phase followed by the

crackr'delamination growth up the final failure.

The combined presence of a 45° oriented layer at the adhesive-adherend interface

and a fillet corner geometry delays the crack nucleation with respect to the square

edge configuration.

The presence of a 45° layer interface complicates significantly the damage evolution

with respect the 0° layer interface. Alter nucleation. cracks and deiaminations

propagate at the adhesive-adherend interface or following interlaminar andfor

intralaminar paths. As a result. the resistance to crack propagation is increased.

The use of microscopic observations of the damage on the polished edges of the

joints turned out suitable to provide information representative of the damage

evolution over the entire joint width.

The complexity of the damage evolution and the long time required for an accurate

optical observations for the assessment of the crack growth suggest the need for an

alternative approach for the damage and crack length monitoring. As a possible

solution. an engineering stiffness-based approach for the crack length measurement

has been presented by the authors (see reference ['i]).

R E F E R E N C E S

Quaresimin M. Ricotta M. (2006) ComposSci Technol. 66:2. 176-187.

|..

Renton W J., Vinson .l R.( l 975). JAircraji, l2 (5), 442-447.

2..

Ferreira J A M., Reis P N.. CostaJ D M.. Richardson M O W.(2002), CamposSci

3..

Technol, 62, 1373-1379.

4

De Goeij W C., Van Toorerl M J L., Beukers A. (1999). Mater Design. 20. 213-221.

5

Johnson W S, Mall S. (1986), J CamposTech Res, 8. 3-7.

6

Meneghetti G., Quaresimin M., Ricotta M. (2009). in press. In: J Fatigue,

doi: 10. l 0 l 6r’j.ijfatigue.2009.02.008

Lusiani M., Meneghetti G., Quaresimin M., Ricotta M. (2008), Proceedings of

‘I

E C C MI3. 13"‘ European Conference on Composite Materials June 2-5 2008.

Stockholm, Sweden.

Quaresimin M. and Ricotta M. (2006). in! J’ Fatigue, 28, 1 166-1 I76.

8

976