Papers by Author: Carlos A. Ramos

Abstract: In this study the embedding of piezoelectric ceramics in carbon-fibre/epoxy laminates is studied with the purpose to be used for structural health monitoring from vibration measurements. Piezoelectric elements were embedded in two laminate types made of two weaved prepregs and with four additional unidirectional prepregs, respectively. The efficiency of the embedding process was analysed from the capability of the piezoelectric ceramic to transmit vibrations to the composite plate. The sensing element was successfully used to monitor the composite plate when submitted to three-point bending dynamic tests at different frequencies.

Abstract: In this work the actuator performance of a ceramic piezoelectric device is studied. Its ability of deforming a Carbon Fiber Reinforced Plastic (CFRP) laminate is measured in the absence/presence of mechanical constraints. Deformation and bending of the CFRP laminate is obtained when a voltage is applied to the piezoelectric device. This deformation was assessed using ESPI technique and a very good agreement with the expected values for the unconstrained case was observed. When completely embedded a reduction of 86% in the piezoelectric response is expected. Finite Element Analysis confirmed the obtained experimental data and a very good linearity in the response was observed.

Abstract: The objective of this work was to study, understand and evaluate the effect of different geometric configurations of carbon plies, in the reflected wavelength spectrum of Bragg grating structure together with the effect of the recoating process of the sensor. The different possibilities depend upon the orientation and location of the optical fibre relative to the composite reinforcement orientation and the presence/absence of recoating. The material stacking sequence and the cure conditions were are also studied and the influence of the different possibilities was considered. The optical spectrum response obtained by the interaction of the optical fibre with the host material is shown.

Abstract: Structural health monitoring of composite structures may be accomplished by measuring strains with embedded optical fibre sensors. In this paper, we present the performance of Bragg grating sensors, which are embedded into a carbon composite laminate and them bonded to the structure in analyse. The paper will briefly discuss the results and compare them with a free fibre Bragg grating bonded in the surface of the carbon composite laminate, with existing electrical strain gauge installation and with a numerical analysis by the finite element method.