Use Of Composite Plates Research Articles

OSCILLATIONS OF LAYED STRUCTURES WITH CONSOLIDATED MECHANICAL CHARACTERISTICS

Modern industry requires the creation and use of materials and structures with improved performance. Such structures include layered structures made of com-posite materials. Layered systems made of high-strength composite materials with different layers have found wide application in aviation technology as elements of the bearing surfaces of aircraft, as well as in many other industries. The use of composite plates in loaded structures is one way to improve the weight characteristics of rocket and space technology. Also layered structural elements are widely used in transport engineering, used in construction practice. Multilayer systems in the conditions of bending deformation are the most rational in terms of strength and rigidity. Thus, the improvement of methods for calculating inhomogeneous layered structures is an urgent task. Along with the methods of non-destructive testing, defectoscopy of structures using hardware methods, analytical research methods remain relevant, which allow to predict the possible destruction of the structure. When designing equipment, it is necessary to take into account the real operating conditions of structures. In the process, the mechanisms work under the action of vibration loads, so determining the dynamic characteristics of structures is an urgent task. This determines the need to study the oscillating processes taking into account the real conditions of vibration load, which will determine the optimal design parameters and modes of operation of the machine with the maximum distance from critical modes that are dangerous. One of the reasons for the destruction of elements of machine-building structures is that they resonate. Therefore, the problem of forced oscillations needs to be solved. To solve this problem, it is necessary to determine the natural frequencies and their corresponding natural forms of oscillations. The paper presents a method of calculating a layered structure to determine the physical characteristics for the whole package, taking into account the physical and mechanical characteristics of each of the layers. This approach allows to determine the dynamic characteristics and stress-strain state of multilayer composite structures, using classical equations for homogeneous struc-tures. This approach greatly simplifies the equation and allows you to find a solution that can be used in the design of structures made of composite materials under vibration loads.

A vibro-acoustic quality control approach for the elastic properties characterisation of thin orthotropic plates

Many engineering structures are built by assembly of plates, and in recent years there has been a widespread use of composite plates, and in particular of orthotropic plates, to improve dynamic structural performance and reduce structural weight. Depending on the manufacturing process used, orthotropic plates might be affected by variability of the mechanical properties, which in turn will affect their performance. The four elastic constants of orthotropic plates can be obtained via direct static or dynamic tests, or via inverse methods which combine dynamic experiments with mathematical models. However these approaches may not be appropriate for establishing manufacturing variability across a number of manufactured plates, since they might require expensive testing equipment and they may be time consuming. In this paper an inverse procedure based on the Chladni patterns is investigated to analyse thin orthotropic rectangular plates. A detailed mathematical derivation of the equations needed for estimating the elastic constants based on the knowledge of five natural frequencies is presented. The repeatability and reproducibility of the results obtained with the proposed procedure is first assessed, and the evaluation of the manufacturing variability of an ensemble of “nominally identical” plywood plates with the proposed approach is then investigated.

Modeling and reduction of shocks on electronic components within a projectile

Electronic components within a projectile are subjected to severe loads over an extremely short duration during the launch process. Failure of these components during launch can result in negative effects on the mission of the projectile. While experimental data can be helpful in understanding failure of electronic components within a projectile, collecting such data are usually difficult. There are also limitations on the reliability of sensors under these circumstances. Finite element modeling (FEM) can offer a means to better understand the behavior of these components. It can also be used to develop better shock mitigation features into the projectile design. This research has two objectives. The first objective is to develop an FEM that one describes the interaction of a typical projectile with the gun barrel during launch. The projectile includes a payload of a one-pound mass representing a typical electronic package supported by a plate. The second objective of this work is to investigate the use of composite plates to support electronic payload as a means to reduce the transmitted shocks during the projectile launch event. The proposed plate has carbon fibers embedded in an epoxy matrix. A parametric study of the effects of varying the thickness of the supporting plate and the fiber volume fraction on the accelerations and stresses is included. Results of the study are used to reach general recommendations regarding reducing failure of electronic components within a projectile.

Effect of Environmental Exposure on the External Strengthening of Concrete with Composites-Short Term Bond Durability

The pressing need for rehabilitation and retrofit strategies that encompasses new and emerging materials and technologies, results from the need to simultaneously repair existing structures while attempting to increase both their performance levels and life spans. A large number of techniques currently exist for strengthening highway bridges ranging from the use of external post-tensioning to the addition of epoxy bonded steel plates to the tension surface. The use of composite plates for the purpose of external reinforcement has considerable potential. However, there is a critical need to investigate the degradation of the composite-concrete interface after exposure to environmental conditions that include moisture, sea water, freezing and freeze-thaw. In this investigation, the effect of five different environmental conditions on the performance of plated beams is considered from aspects related to materials and durability. It is shown that the selection of the appropriate resin system is critical to success, and the dangers of selecting systems with low glass transition temperatures and drastic drops in instantaneous modulus as a function of temperature are discussed. Two different resin systems are compared using the same fibrous reinforcement and an overall view of durability at the concrete-composite interface is elucidated.