## 1 Introduction  
Recently, the research relevant to the piezoelectric materials to control the vibration of structures is actively reported in the literature. The applications of the piezoelectric materials are vibration suppression, shape control, active damping, size control, and energy harvesting, etc. The materials can be used as sensors and actuators. At first, direct piezoelectric effect means that the materials generate an electric charge while the model is subjected to a mechanical deformation. Conversely, they could be deformed when some electric charges are applied to structures. This is called the converse piezoelectric effect. Many engineers have studied composite structures with piezoelectric sensors and actuators. [PERSON] [1] investigated theoretical formulations and finite element models using the shear deformation plate theories. They analyzed the laminated plates with sensors and actuators under mechanical and electrical loads. [PERSON] et al. [2] presented the active vibration suppression of the laminated composite plates. [PERSON] and [PERSON] [3] also simulated theoretical formulation for the plates with piezoelectric materials. [PERSON] and [PERSON] [4] showed the mechanics analysis and performances of piezolaminated plate and shell structures. In addition, [PERSON] et al. [5] described the finite element analysis of the piezoelectric transducer. The model of multilayer piezoelectric actuators is derived based on the physical analysis by [PERSON] et al. [6]. The proposed methods are easy to handle and apply the piezo models. Furthermore, [PERSON] [7] presented the design, optimization, and testing of piezoelectric harvesters for energy scavenging from human walking. Also, [PERSON] et al. [8] designed a self-powered and wireless radio frequency (RF) transmission device using by combination of triboelectric nanogenerator (TENG) and off-the-shelf piezoelectric element. On the other hand, the dynamic responses of structures under air blast loads have been studied for many years. [PERSON] et al. [9] showed the evaluation of pressures and impulses produced by blast loads with the aid of hydrocodes. The numerical and experimental research of a stiffened laminated composite panel under a shock wave was represented by [PERSON] and [PERSON] [10]. Furthermore, [PERSON] et al. [11] analyzed numerical responses of metallic panels subjected to explosive loadings. Recently, research and development of stiffened structures is one of the important subjects in aircraft and aerospace industries. Globally, many engineers have tried to increase the stiffness by using composite stiffened structures in the space launch vehicle. Nowadays, [PERSON] et al. [12; 13] studied active vibration control and sound radiation from a rib stiffened panel using velocity feedback method. Also, [PERSON] et al. [14] presented the dynamic analytical solution of piezoelectric stack using piezo-elasticity theory. In addition, [PERSON] et al. [15] studied the dynamic behaviors of stiffened composite model with piezoelectric patches under airflow. The blast loads applied a sharp pressure to the composite structure in a moment. Though numerous studies on piezoelectric stiffened models have been performed widely up until now, research to suppress the vibrations of stiffened models caused by aerodynamic flows such as blast loads has been studied in a limited range. In other words, many studies have been focused on damages to the structures. Therefore, active vibration suppression of piezoelectric stiffened laminated panels subjected to normal blast waves is studied in this paper. Due to the characteristics of piezoelectric materials as fast responders, the vibration behaviors of stiffened composite panels could be controlled easily by piezoelectric actuators under a blast loading. A stiffened panel with piezoelectric effect is formulated using finite element method. Numerical formulations and results are verified with previous data.