Integration of Networks of Sensors and Electronics for Structural Health Monitoring of Composite Materials

The low-cost, widespread availability and robust nature of current electronic devices suggest the feasibility of creating a composite structure with integrated networked sensors to monitor in real time the life of civil and aerospace structures while in service conditions. For structures that need to survive to high number of life cycles under varying load-environmental conditions, it is of crucial importance that the strength, stiffness, endurance, and general load-bearing capabilities of the composite not to be severely degraded by the integrated networked components. Therefore, design tools must be developed to achieve optimized, safe, and reliable structures. High values of stress concentrations due to the presence of a rigid device within a highly anisotropic material can trigger the initiation of microcracks in the resin matrix. To quantify these effects, the acoustic emission technique is used to characterize the initiation of microfailures within laminated composites with integrated electronics. 1. Introduction Health monitoring of composite structures and components for civil and aerospace applications has become of major interest in the past few decades. Advances in the microelectronics industry are clearly showing progressive success at achieving smaller chip and sensors sizes of consuming less power, while increasing the processing and functionality. However, such inclusions may affect the local integrity of fiber reinforced polymers and the limitation of the tolerability of the host material in presence of these devices must be quantified. With respect to structural performance, the effects of the embedded transducers on the host composite may be object of concern. The presence of inclusions causes material and geometrical discontinuities that are responsible of unwanted stress concentrations with consequences on the reduction of the stiffness and the overall material performance. For this reason, effort has been devoted into adding monitoring functionality into composites without compromising the structural integrity. To emphasize the importance of these studies a brief review of the literature which includes the first historical and significant contributions in this area is needed. These contributions are summarized in Table 1. Table 1: List of some significant experimental contributions on the evaluation of the effects of integrated devices on the structural integrity of composite materials. By reviewing these experimental studies, and as pointed out in a previous work [16], it appears that in cases where the thickness and the geometry