Proc. SPIE. 10168, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2017
KEYWORDS: Optical fibers, Modeling, Aerospace engineering, Fiber Bragg gratings, Sensors, Composites, Structural health monitoring, Finite element methods, System identification, Optical networks, Chemical elements, Systems modeling
Technologies based on optical fibers provide the possibility of installing relatively dense networks of sensors that can perform effective strain sensing functions during the operational life of structures. A contemporary trend is the increasing adoption of composite materials in aerospace constructions, which leads to structural architectures made of large monolithic elements. The paper is aimed at showing the feasibility of a detailed reconstruction of the strain field in a composite spar, which is based on the development of reference finite element models and the identification of load modes, consisting of a parameterized set of forces. The procedure is described and assessed in ideal conditions. Thereafter, a surrogate model is used to obtain realistic representation of the data acquired by the strain sensing system, so that the developed procedure is evaluated considering local effects due to the introduction of loads, significant modelling discrepancy in the development of the reference model and the presence of measurement noise. Results show that the method can obtain a robust and quite detailed reconstruction of strain fields, even at the level of local distributions, of the internal forces in the spars and of the displacements, by identifying an equivalent set of load parameters. Finally, the trade-off between the number of sensor and the accuracy, and the optimal position of the sensors for a given maximum number of sensors is evaluated by performing a multi-objective optimization, thus showing that even a relative dense network of externally applied sensors can be used to achieve good quality results.
Deformable mirrors actuated by smart structures are promising devices for next generation astronomical instrumentation.
The piezo technology and in particular piezoceramics is currently among the most investigated
structural materials. Fragility makes Ceramic materials extremely vulnerable to accidental breakage during bonding
and embedding processes and limits the ability to comply to curved surfaces (typical of mirrors). Moreover
lead-based piezoceramics typically have relevant additional masses. To overcome these limitations, we studied
the applicability of composites piezoceramics actuators to smart structures with these purposes. We developed
a combined Finite Element and Raytracing analysis devoted to a parametric performance predictions of a smart
Piezocomposites based substrate applicable to deformable mirrors. We took in detail into account the possibility
to change the focal length of the mirror keeping a satisfactory image quality. In this paper we present a specific
type of Piezocomposite actuators and numerical/experimental techniques purposely developed to integrate them
into smart structures. We evaluated numerical and experimental results comparing bonding and embedding of