Serge Abrate

Impact on Laminated Composites: Recent Advances

Impact damage in structures made out of composite materials is a major concern since such damage can be introduced during the life of the structure, and its mechanical properties can be drastically reduced as a result. In a previous review of the literature on impact on composite materials, this author considered 285 published before 1989. In this article over 300 articles most of which appeared after 1989 are reviewed. These figures indicate that this is a very active area of research, and the present paper seeks to present a comprehensive view of the latest developments. Taken together, these two reviews present a comprehensive view of the state of knowledge in the area. Most the current research effort is focused on low velocity impact damage and, in particular, the damage predictions and the evaluation and prediction of residual properties of damaged laminates. A significant number of papers deal with ballistic impacts on laminated composites and the use of composite materials in designing light armor.

Vibrations of belts and belt drives

Abstract During its operation, a power transmission belt can undergo axial, transverse and torsional motion. Models available for analyzing the free and forced vibrations of the belt are discussed. The effects of initial tension, transport velocity, bending rigidity, support flexibility, large displacements and belt and pulley imperfections are discussed. Vibrations of belt drives are also considered, and the influence of several complicating factors are mentioned. This article reviews the state-of-the-art in vibration analysis of power transmission belts. Many contributions found in the literature are brought together, and some new results are also included.

Matrix cracking in laminated composites: A review

Abstract This article presents an overview of the problem of matrix cracking in laminated composite materials. The parameters governing the onset and accumulation of internal damage under several types of loadings are reviewed. The analysis of laminates with matrix cracks can be performed using a shear-lag model, variational, elasticity, finite element or finite difference approaches. Prediction of further cracking is based on either a fracture mechanics approach or a probabilistic failure strength theory. Continuum damage mechanics are used by some investigators to model the behavior of the cracked laminate. Recent developments in this area are summarized here, and suggestions for future research are presented.

Vibration of point-supported rectangular composite plates

Abstract A general approach is presented to study the free vibrations of rectangular symmetrically laminated composite plates with point supports by using the Rayleigh-Ritz method and the Lagrange multiplier technique for enforcing the zero displacement constraints at the support locations. Polynomial approximation functions are used and the constitutive relationships are written in terms of four lamination parameters. With these lamination parameters, the number of design variables is reduced to a minimum, which is useful for design optimization purposes, while all symmetric lay-ups are considered. This paper illustrates how the lamination parameters can be used for optimal design of vibrating plates. Results are presented for several cases and the effect of aspect ratio, material properties and lay-up are fully investigated. Plates on point supports and with straight and curved internal line supports are considered. For each case, the lay-up that maximizes the first natural frequency of the plate is determined.

Vibration of composite plates with internal supports

Abstract The free vibration of rectangular laminated composite plates with arbitrary support conditions along the edges, internal line supports and discrete point supports are studied using the Rayleigh-Ritz method. Polynomial approximation functions are selected to satisfy all essential boundary conditions along the edges of the plate and to vanish along line supports parallel to the co-ordinate axes. Straight line supports at an angle from the co-ordinate axes and curved line supports are modeled by introducing several point supports along the line. Zero displacement constraints at the point support locations are enforced using the Lagrange multiplier technique. The plate constitutive equations are expressed in terms of stiffness invariants and the fundamental natural frequency is maximized by selecting the appropriate lay-up. Several examples are presented to illustrate the versatility of the approach and provide results not previously available. The influence of the number of plies in the laminate, lay-up, material properties and plate aspect ratios are investigated.