## 1 Introduction  
Functionally graded (FG) cylindrical panels are largely used as structural members in many industrial applications such as aerospace vehicles, nuclear equipment, petro-chemical structures, among others. FG structures usually operate under high thermal conditions, which can yield a vibratory motion, especially when subjected to a sudden variation of the thermal conditions. On the other hand, the mechanical behavior and the vibration control of FG cylindrical panels can be improved by introducing piezoelectric layers at their inner and/or outer surfaces. This requires an accurate evaluation of the thermoelastic properties of FG cylindrical panels, with attached piezoelectric layers under a thermal shock loading, for design and manufacturing purposes. In this context, it is well known that a conventional Fourier heat conduction law is unable to predict the temperature distribution and heat wave propagation within a continuum at the initial phase. On the other hand, an uncoupled classical thermoelastic approach cannot accurately predict the thermoelastic behavior of a body under a thermal shock. Countermeasures against these limitations have encouraged the development of different coupled thermoelasticity theories [1; 2; 3]. Among them, the Lord and Shulman (L-S) generalized thermoelasticity theory is one of the simplest formulations applied in the literature [4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14], which includes a relaxation time and a coupling between thermal and mechanical energies [1]. In this framework, some interesting thermoelastic studies based on an uncoupled classical thermoelasticity theory of FG cylindrical panels and shells can be found in [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31]. These studies considered the possible presence of piezoelectric layers, and estimated the temperature distribution of a body by means of a Fourier heat conduction law. On the other hand, many works, in literature, have applied a non-Fourier heat transfer law or coupled theories to study the thermoelastic response of FG structures [32; 33; 34; 35; 36; 37]. More specifically, [PERSON] et al. [32] explored the capabilities of a refined finite element approach based on the L-S generalized theory of thermoelasticity and Carrera Unified Formulation (CUF) for the 3D thermoelastic analysis of FG disks exposed to a thermal shock loading. [PERSON] et al. [33] employed a generalized fractional Cattaneo-type heat conduction model to analyze the thermal shock problem of elastic FG strips with internal cracks, while using a Fourier and Laplace transforms for an analytical computation of the thermoelastic field unknowns. [PERSON] et al. [34] presented a unified formulation for the bending response of FG plates under a transient thermal loading in the framework of the L-S generalized thermoelasticity and two-dimensional plate theories. In their work, the authors applied a meshless method and a Wilson time integration scheme to solve numerically the governing equations of the problem. In line with the previous works, [PERSON] and [PERSON] [35] applied the non-Fourier heat conduction equations to determine the temperature distribution and the induced thermal stresses and deformations, in carbon nanotube-reinforced composite cylindrical panels subjected to a heat pulse. They assumed temperature-dependent material properties and applied a differential quadrature method (DQM) to discretize the governing equations and solve the problem numerically. [PERSON] and [PERSON] [36] studied the propagation of thermoelastic waves in laminated spherical shells with temperature-dependent material properties and FG layers under thermal boundary conditions according to the L-S generalized thermoelasticity. [PERSON] et al. [37] investigated the thermo-mechanical wave propagation in composite spherical shells reinforced with multilayer functionally graded graphene platelets under a thermo-mechanical shock loading.