University of Kassel (Germany), Institut für
Werkstofftechnik
Present address: : Fraunhofer-Institut für Kurzzeitdynamik,
Ernst-Mach-Institut (EMI), Eckerstrasse 4, 79104 Freiburg (Germany) Phone: (+49)
761-2714-416, Facsimile:(+49) 761-2714-316 E-mail: Gassan@emi.fhg.de
(Received 12/99; accepted 3/00)
ABSTRACT
This paper is dealing with a new method based on determining on-line loss energy as
measure of the state of damage of composite materials under tension-tension fatigue
loadings. Experimentally, cross-ply glass-fibre epoxy composites with a fibre volume
fraction of 0.4 and differences in fibre-matrix adhesion and matrix ductility were tested
by a stress-ratio of 0.1 and frequency of 10 Hz. The paper shows, that the on-line
measured loss energy is very sensitive to evaluate the damage state of composite
materials. Number of load cycles between a new defined state of damage (damage state
‘A’ in that paper) and final failure for a giver n/N ratio is shown to be sensitive to
characterise differences in composite morphology such as level of interfacial strength and
matrix ductility. For brittle composites, this damage state ‘A’ can be used to predict
fatigue life of composite materials.
