Damping Capacity Of Composites Research Articles

Effect of Ti and Mg on the damping behavior of in situ aluminum composites

Damping capacity of in situ TiB2 particulate reinforced aluminum composites with Ti and Mg excess were investigated. The composites were fabricated with an exothermic reaction process via K2TiF4 and KBF4 salts. The damping behavior of materials over a temperature range of 30–300 °C was investigated by using a dynamic mechanical thermal analyzer. Experimental findings indicate that the damping capacity of composites with Ti, Mg excess, respectively is lower than that of Al/5 wt.% composite when temperature is below 180 °C and is higher than of Al/5 wt.% composite above 180 °C. The main effects of these elements are the formation of thin layers on TiB2 particulates, which resulted in the change of damping capacity.

FEM based damping studies of metastable Al/Ti composites

In the present study, the damping capacity of a metal matrix composite is predicted using a micro-mechanical modelling approach. The model is based on finite element analysis of an axisymmetric unit cell, which mimics a pure metallic cylinder with a stiff reinforcing spherical particulate placed at the center. The energy dissipated by the composite is numerically predicted using the unit cell by applying a harmonic load, taking into account the viscoplastic behavior of the processing induced residual plastic strain at the matrix–reinforcement interface of the composite. The model shows that the plastic zone size increases with volume fraction of Ti added which results in a proportional increase in the damping capacity of the composite. The model was validated by comparing the numerical results against an impact based suspended beam experiment conducted at low strain amplitude on Al/Ti samples with different volume fractions of Ti particulates.

Effect of fiber coating on the longitudinal damping capacity of fiber-reinforced metal matrix composites

A novel model for calculating the damping capacity of continuous fiber-reinforced metal matrix composites (FMMCs) is proposed based on the viewpoint of energy loss. Finite element method (FEM) has been employed to investigate the effect of fiber coating on the longitudinal damping capacity of a composite by varying the thickness and the material properties of the coating. The results show that the damping of a composite containing the elastic coating increases with a decrease in the elastic modulus of the coating, while for the case of plastic coating, the weak coating or the high elastic modulus coating may help in improving the overall damping of composite.

Effects of interply damping layers on the dynamic characteristics ofcomposite plates

Integrated damping mechanics for composite plates with constrained interlaminar layers of polymer damping materials are developed. Discrete layer damping mechanics are presented for composite laminates with damping layers, in connection with a semianalytical method for predicting the modal damping in simply supported specialty composite plates. Correlations between predicted and measured response in graphite/epox y plates illustrate the accuracy of the method. Additional application cases for graphite/epoxy plates of various laminations demonstrate the potential for higher damping than geometrically equivalent aluminum plates. The effects of aspect ratio, damping layer thickness, and fiber volume ratio on static and dynamic characteristics of the composite plate are also investigated. AMPING is a significant dynamic parameter for vibration and sound control, dynamic stability, positioning accu- racy, fatigue endurance, and impact resistance. Many current structural applications (e.g., large space structures, engine blades, and high-speed machinery) require light weight and high dynamic performance. Therefore, candidate sources of passive damping should add minimal parasitic weight and be compatible with the structural configuration. Two potential damping sources satisfying the previous re- quirements are the constrained damping layer approach and the damping capacity of composites. Constrained damping layers in isotropic metallic structures have been widely applied and investigated.1 They provide high damping, but tend to increase the structural weight and offer limited means for damping tailoring. The inherent damping capacity of compos- ite materials also seems promising. Although the damping of composite structures is not very high, it is significantly higher than that for most common metallic structures. Moreover, composites are the materials of preference in many cases, since they readily provide high specific stiffness and strength. More importantly, research on the damping mechanics of composite laminates2'4 and structures5'6 has shown that composite damp- ing is anisotropic, highly tailorable, and depends on an array of micromechanic al, laminate, and structural parameters. It has been further demonstrated that optimal tailoring may significantly improve the damped dynamic performance of composite structures.7 It seems likely that the combination of both approaches (i.e., composite structures with interlaminar damping layers) will offer the advantages of high damping, damping tailoring, good mechanical properties, and low weight addition. In addi- tion, the interlaminar damping concept is highly compatible with the laminated configuration of composite structures and their fabrication techniques. In contrast to isotropic materials, the variations in anisotropy and elastic properties of each