# Passive Multi-Layer Composite Damper of Flat Belt Tensioner Idler
## 1 Introduction  
The control and elimination of unwanted vibrations in mechanical systems is important due to the potential for premature failure of critical components and noise reduction. Natural approaches to control vibrations include reducing excitation or altering the design by modification of the mass and/or stiffness. These approaches have limitations because traditional homogeneous materials are very good conductors of both vibrational and acoustic energy. The trend of increasing operational speeds to achieve high profits and reduce the mass of structures provides opportunities to develop new designs using materials with high damping capabilities and high specific modulus (\(E/\rho\)). Composite materials and layered sandwich structures with the appropriate performance levels have been developed and applied in dynamically-loaded structures, such as vehicles, planes, and machinery. The techniques used to control vibrations can be classified as active or passive, with an additional semi-active control technique. The advantages of a passive damper are that no power source is needed, it is inexpensive, and it is easy to implement. However, a limitation of passive control systems is that they are not capable of adapting to different types of excitation. Moreover, in general, passive vibration control is for a middle-to-high frequency range [1]. Vibration energy is dissipated in structures by different mechanisms throughout the structure. According to [2], there are three fundamental modes of dissipation: (i) Within a solid, (ii) within or into a fluid medium, and (iii) at interfaces between solids or between solids and fluids. The application presented herein uses the principle of dissipation within solids by material damping during cyclic motion. Traditional structural metals have high stiffness but low material damping properties, while materials with high material damping are typically of low stiffness. Materialsthat have both high stiffness and damping are not common and have to be specially designed, for example, in the form of layered composite structure dampers. The internal friction of composite materials and composite structures has the specific features required. Microplastic or viscoelastic (inelastic) phenomena associated with the matrix and the relative slipping at the interface between the matrix and the reinforcement are the main sources of internal damping in a composite material [3]. The mechanisms of energy dissipation and physical explanation are still the subject of research. [4]. Passive damping systems have been developed and are utilized in civil engineering for earthquake energy dissipation systems and noise reduction. Passive systems include tuned mass dampers (TMDs), particle TMDs, tuned liquid particle dampers, tuned liquid column dampers (TLCDs), eddy-current TMDs, tuned mass generators, tuned-inerter dampers, magnetic negative stiffness devices, resetting passive stiffness dampers, re-entering shape memory alloy dampers, viscous wall dampers, viscoelastic dampers, and friction dampers [5,6]. In mechanical engineering, dampers are mainly utilized in vehicles, planes, and machinery. However, the usage of various passive dampers is increasing with the development of composites with a polymeric matrix or sandwich structure. Polymeric damping layers exhibit a peak value in damping from 0.1 to 1 or more and are commonly used to add damping to structural members [7]. Passive dampers usually consist of monolithic viscoelastic damping layers (constrained or unconstrained) that are attached to the base structure and passively dissipate vibration energy [8] or a viscoelastic material is sandwiched between layers [9]. In actual research, the traditional monolithic viscoelastic layer involves other elements, such as a graphite phase [10]. Moreover, passive dampers can involve particles [11,12], periodic sandwich plates [13,14], a honeycomb structure of cells filled with circular carbon tubes forming a composite sandwich structure [15], or a damping layer that can be formed from open-cell foam [16].