Author(s):
Campilho, Raul 
; Moura, Daniel ; Gonçalves, Daniel ; Silva, João ; Banea, Mariana D. ; Silva, Lucas F. M. da
Date: 2013
Persistent ID: http://hdl.handle.net/10400.22/3443
Origin: Repositório Científico do Instituto Politécnico do Porto
Subject(s): Fibres; Fracture toughness; Damage mechanics; Joining
Description
Adhesive bonding has become more efficient in the last few decades due to the adhesives developments,
granting higher strength and ductility. On the other hand, natural fibre composites have recently gained
interest due to the low cost and density. It is therefore essential to predict the fracture behavior of joints
between these materials, to assess the feasibility of joining or repairing with adhesives. In this work, the
tensile fracture toughness (Gc
n) of adhesive joints between natural fibre composites is studied, by bonding
with a ductile adhesive and co-curing. Conventional methods to obtain Gc
n are used for the co-cured specimens,
while for the adhesive within the bonded joint, the J-integral is considered. For the J-integral calculation,
an optical measurement method is developed for the evaluation of the crack tip opening and
adherends rotation at the crack tip during the test, supported by a Matlab sub-routine for the automated
extraction of these quantities. As output of this work, an optical method that allows an easier and quicker
extraction of the parameters to obtain Gc
n than the available methods is proposed (by the J-integral technique),
and the fracture behaviour in tension of bonded and co-cured joints in jute-reinforced natural
fibre composites is also provided for the subsequent strength prediction. Additionally, for the adhesively-
bonded joints, the tensile cohesive law of the adhesive is derived by the direct method.
