Damage redirection and healing in skin-stiffener debonding specimens under fatigue conditions

Damage redirection and healing in skin-stiffener debonding specimens under fatigue conditions

Luterbacher, R.
Bond, I.P.
Trask, R.S.

2013-06-16

Locally stiffened or ‘stringer’ - skin composite structures are extensively used for lightweight applications in the aerospace industry. Due to localised stiffening, stress concentrations arise which can initiate damage e.g. debonding or delamination, within the composite structure. Critically, this damage can propagate under fatigue loading compromising the structural integrity of the component. To mitigate against this risk, significant safety margins are used within the design phase, which limit the potential weight savings offered by the application of advanced fibre reinforced composites. In this study, the potential to redirect propagating cracks away from critical failure paths and into dedicated self-healing zones has been investigated through the use of thermoplastic interleaves (for redirection) and an embedded vascular network (to mitigate the damage). One of the major challenges in employing a vascular network is to ensure the connectivity between the propagating damage and the vascules. A self-healing agent (low viscosity epoxy resin) was delivered via the vascular network in order to restore the mechanical performance of the deteriorated structural element. A number of different interleave – vascule configurations have been investigated, all successfully redirecting the propagating fatigue damage into the vascules within skin-stiffener debonding specimens. The tensile and fatigue tests performed have shown that these modifications are not detrimental to the mechanical performance in comparison to a baseline configuration. Moreover, the interleave configurations are able to redirect the interfacial damage, between the skin and the stiffener, towards the self-healing functionality embedded within the laminate. During fatigue loading, a notable stiffness loss is observed as the damage propagates. After the healing event, the stiffness in both static and fatigue conditions has been successfully restored.

fibre reinforced composite
adhesive joint
self-healing
vascular network
interleaves
delamination

http://resolver.tudelft.nl/uuid:ec185488-8cca-4850-8bf2-d87fc78e432d

Conference proceedings

conference paper

(c) 2013 Luterbacher, R.; Bond, I.P.; Trask, R.S.