Fracture toughness of a laminated composite

Document type: Bookchapters
Full text:
Author(s): Sharon Kao-Walter, Per Ståhle, Rickard Hägglund
Title: Fracture toughness of a laminated composite
Book: Fracture of Polymers, Composites and Adhesives II
Year: 2003
Pagination: 355-364
ISBN: 0-08-044195-5
Publisher: Elsevier
Organization: Blekinge Institute of Technology
Department: Dept. of Mechanical Engineering (Institutionen för maskinteknik)
Dept. of Mechanical Engineering S-371 79 Karlskrona
+46 455 38 50 00
Authors e-mail:
Language: English
Abstract: The fracture toughness of a polymer-metal laminate composite is obtained by mechanical testing of a specimen containing a pre-crack. The result is compared with a calculated fracture toughness based on the measured fracture toughness of the individual layers. The laminate is a material used for packaging. It consists of a thin aluminium foil and a polymer coating. A centred crack panel test geometry is used. Each of the layers forming the laminate is also tested separately. It is observed that the load carrying capacity increases dramatically. At the strain when peak load is reached for the laminate only aluminium is expected to carry any substantial load because of the low stiffness of the LDPE. However, the strength of the laminate is almost twice the strength of the aluminium foil. The reason seems to be that the aluminium forces the polymer to absorb large quantities of energy at small deformation. The result is compared with the accumulated toughness of all involved layers. A more elaborate model is proposed in the light of non-linear material behaviour and development of a fracture process zone at the crack tip. Possible fracture of the interface between the layers is discussed.
Subject: Mechanical Engineering\Structural Mechanics
Mechanical Engineering\General
Keywords: Laminate, aluminium foil, polymer, crack, fracture toughness