Integration of Networks of Sensors and Electronics for Structural Health Monitoring of Composite Materials
Table 1
List of some significant experimental contributions on the evaluation of the effects of integrated devices on the structural integrity of composite materials.
Unidirectional and quasi isotropic graphite laminates
Failure does not initiate near the fiber-optic sensor. No sensitivity to the embedded sensor is seen in quasi-isotropic cases The transverse strength is reduced.
Optical microscopy and Moiré interferometry show no perturbation in the strain state of the material with embedded FO. The material lay-up and its thickness influence the results.
4% reduction of strength and Young’s modulus. No degradation of the fatigue life. The embedded PZTs maintain a steady output indefinitely if mechanically cycled within their operational strain limits
Static tension and tension-tension fatigue of interlaced materials with devices: 33% reduction of strength; endurance is improved; damage initiation delayed with respect to the use of cut-out methods.
Zirconate-titanate, PZT actuators integrated with cut-out methods. Device size: 50.8 mm 25.4 mm 0.254 mm
AS4/3501-6 graphite/epoxy laminates
Fatigue of active PZT. Specimens cycled at different max stress levels while exciting the embedded actuator from 10 V to 100 V or 10 V to 100 V. 10 Hz and R = 0.1. Embedded PZT performed better in the out-of-phase than in-phase conditions.
Tensile strength and Young’s modulus are not affected by the integration of actuator/sensor using the two embedding techniques. No degradation in the fatigue life/strength. The PZT actuator/sensor functions mechanically fatigued or loaded to the maximum stress level equal to its operational design limit.
Samples with 0, 30, 45, 60, FO sensors oriented with respect the fibers direction.
Unidirectional AS4/3501-6 carbon/epoxy laminates
The material properties are unaffected by the integration of the fiber-optic sensor. 10% reduction of the tensile strength and 40% decrease of the compressive strength are reported.
Active flexible piezoceramic sensors and actuators patches. Patches dimensions: 135 mm 55 mm 0.33 mm.
Plain weave carbon/epoxy material
(1) Cutout holes, (2) molded-in holes, and (3) embedding techniques. Manufacturing, durability, dynamic, and structural performance of embedded materials are optimal if materials with devices are made with method (3)