Mechanical behavior and health monitoring by Acoustic Emission of unidirectional and cross-ply laminates integrated by piezoelectric implant Sahir Masmoudi a,b,⇑ , Abderrahim El Mahi a , Saïd Turki b , Rachid El Guerjouma a a LUNAM University, Maine University, Acoustic Laboratory of Maine University (LAUM) CNRS UMR 6613, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France b Sfax University, Faculty of Sciences of Sfax, Department of Physics BP1171, 3000 Sfax, Tunisia article info Article history: Received 12 August 2013 Received in revised form 4 April 2014 Accepted 12 April 2014 Available online xxxx Keywords: Laminates Piezoelectric implant Three-point bending Static Creep Acoustic Emission Damage abstract Recent progress in sensor technologies, signal processing and electronics has made it possible to fulfill the need for the development of in-service structural health monitoring (SHM) systems. This study presents a health monitoring of composite materials integrated by piezoelectric sensor using Acoustic Emission (AE) technique. A series of specimens of composite laminates with and without piezoelectric implant were subject to three-point bending in static and creep tests while continuously monitoring the response by the AE technique. The analysis and observation of AE signals lead to the identification of the acoustic sig- natures of damage mechanisms in composite laminates. The mechanical behavior of composites with and without integrated sensor shows no difference in the form. The incorporation of piezoelectric sensor influences specially the fracture load and causes low degradation of mechanical properties of materials. One of the major differences between the two types of materials (with and without embedded sensor) is the intense acoustic activity in the integrated material. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction There is a growing need for the development of in-service struc- tural health monitoring systems to rapidly assess the health condi- tion and durability of composite structures. Recent progress in sensor technologies, signal processing and electronics has made it possible to fulfill this demand. New scientific and technological tools are now studied and implemented. They should allow the manufacture of composites incorporating new functional materials that are active or passive electromechanical devices. Piezoelectric, optical fiber and magnetostrictive/electrostrictive materials are some typical examples. The presence of inclusions causes geomet- rical discontinuities that are responsible for reduction of mechan- ical properties, failure strength and the overall material performance [1]. So, it is important to study the effects of embed- ded transducers on the host composite. Many works have been investigated concerning the feasibility of implantation of sensors and devices in composite materials. Also they have evaluated the life time of smart composite materials and they have studied the damage mechanisms and the mechanical behavior of materials under different types of loading e.g. static, fatigue, etc. For example the implant of fiber-optic is studied by Measures [2]. He has reported on several advances and he has made towards the development of fiber-optic sensors for smart structures. This includes tests of a prototype damage-assessment system based on an embedded network of especially damage-sen- sitized optical fibers. He has used the Michelson fiber-optic strain sensors for the detection of damage induced Acoustic Emission and for exploring the potential of an optoacoustic cure monitoring concept. Also he has investigated the use of the intrinsic Fabry– Perot strain sensors and the Bragg grating sensor embedded within composite materials. Piezoelectric materials show a particularly good capacity to sat- isfy exigent applications. These elements can be used as sensors by measuring voltage differences across parallel electrodes when cyclically strained, or alternatively they can be used as actuators by inducing expansion and contraction with an applied alternating electric field. Materials with piezoelectric properties are particu- larly attractive for SHM applications due to their high-frequency response and overall wide-bandwidth characteristics. Most research has indicated piezoceramic elements, specifically PZT (lead zirconate titanate), to be the most suitable for practical http://dx.doi.org/10.1016/j.apacoust.2014.04.011 0003-682X/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: LUNAM University, Maine University, Acoustic Laboratory of Maine University (LAUM) CNRS UMR 6613, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France. Tel.: +33 (0) 243 83 34 56; fax: +33 (0) 243 83 31 49. E-mail address: Sahir.Masmoudi.Etu@univ-lemans.fr (S. Masmoudi). Applied Acoustics xxx (2014) xxx–xxx Contents lists available at ScienceDirect Applied Acoustics journal homepage: www.elsevier.com/locate/apacoust Please cite this article in press as: Masmoudi S et al. Mechanical behavior and health monitoring by Acoustic Emission of unidirectional and cross-ply lam- inates integrated by piezoelectric implant. Appl Acoust (2014), http://dx.doi.org/10.1016/j.apacoust.2014.04.011