Composite Materials Research Progress

In: Composite Materials Research Progress ISBN: 1-60021-994-2
Editor: Lucas P. Durand, pp. 165-207 © 2008 Nova Science Publishers, Inc.
Chapter 5
DAMAGE EVALUATION AND RESIDUAL STRENGTH
PREDICTION OF CFRP LAMINATES BY MEANS
OF ACOUSTIC EMISSION TECHNIQUES
Giangiacomo Minak 1 and Andrea Zucchelli 2
Department of Mechanical Engineering, Alma Mater Studiorum - Università di Bologna,
Viale Risorgimento 2, 40135 Bologna, Italia
Abstract
A new approach that integrates acoustic emission (AE) and the mechanical behaviour of
composite materials is presented. Usually AE information is used to evaluate qualitatively the
damage progression in order to assess the structural integrity of a wide variety of mechanical
elements such as pressure vessels. From the other side, the mechanical information, e.g. the
stress-strain curve, is used to obtain a quantitative description of the material behaviour. In
order to perform a deeper analysis, a function that combines AE and mechanical information
is introduced. In particular, this function depends on the strain energy and on the AE events
energy, and it was used to study the behaviour of CFRP composite laminates in different
applications: (i) to describe the damage progression in tensile and transversal load testing; (ii)
to predict residual tensile strength of transversally loaded laminates (condition that simulates a
low velocity impact).
Introduction
Long fibre reinforced composite laminates are a complex structure at the meso-scale. The
fibres embedded in the matrix constitute the lamina and the overlapping of different laminas
makes the composite laminate. A consequence of this architecture is the complex behaviour
during loading and servicing of components realized by such material, and the multiplicity of
different failure mechanisms that determine the damage progression.
1 E-mail address: giangiacomo.minak@unibo.it
2 E-mail address: a.zucchelli@unibo.it