A. Castellani

Damping characteristics of fabric and laminated Kevlar composites

Abstract A set of experimental tests on damping coefficient measurements for Kevlar fibre composite samples, both fabric and laminated, is presented. The damping coefficient values, which are independent of the composite Youngs modulus value and of the type (fabric or laminate), are greater than typical values for carbon or glass fibre composites. This behaviour can be explained by realizing that in Kevlar composites the fibre behaves as a viscoelastic material and its damping coefficient is of the same order as that of the matrix. The prediction of the damping coefficients by an energy approach validates the experimental results.

Experimental Tests for Damping Measurements on Several Short Glass Fiber Composites

Some experimental tests on the damping measurements for short glass fiber composites are presented. The short fiber samples are of three different fiber orientations: aligned longitudinally, aligned transversely and random. The tested composites have been built for a possible secondary structural use in the field of road transport. A comparison of the gathered data from the damping measurements with theoretically predicted values, gained with a classical approach, is presented. The good agreement between the experimental and theoretical values of the three types of composites shows that it is possible to broaden the application of the theoretical ap proach as used in continuous glass fiber for predicting the damping values of aligned and random short glass fibers. These results also confirm the tight connection between damping and stiffness charac teristics in glass fiber composites.

Thermoelastic behaviour of space structures in composite materials

Abstract In this paper, experimental tests on Kevlar specimens are presented in order to study the mechanical and thermal behaviour of large space structures. In particular tensile strength, tensile and flexural moduli, damping coefficient and thermal expansion coefficient of the style 285 fabric have been evaluated. The experimental values have been compared with the values gained by a previsional program. The results show a non linear behaviour as regards the compressive stress strain characteristics which affects the behaviour under flexural loading. A peculiar point is the damping characteristic that shows a nonlinear behaviour and mean values bigger than for other composite materials as glass fiber or carbon fiber.

Analysis of coupled vibration modes by use of holographic interferometry and finite elements method

A new experimental procedure devoted to analyse deformation patterns due to the contemporary excitation of different vibration modes (mode coupling) is proposed. The proposed procedure, based on use of holographic interferometry techniques, is particularly appropriate whenever coupled modes are expected according to FEM computation and an experimental modal analysis is required for FEM model validation. This work tests the proposed procedure by verifying the reliability of the experimental results worked out in analysing two simple specimens whose modal behavior can be confidently predicted by analytical and numerical computation.

Selecting and Management of Fire Fighter Aircraft

A comparison between the performance and direct operating costs of the water bombers Canadair CL215 and the CL415 Turboprop is presented. These aircraft are designed for fire fighting. The CL215s are currently used by the Italian Forest Service. Considering both the importance of forest-fire combating and the potential market for this type of aircraft, the Italian aerospace industry, Alenia, is designing a new aircraft designated the Advanced Amphibious Aircraft (AAA). On the basis of the design data, a comparison between the AAA and the Canadair CL215 and CL415 is shown. Based upon the Italian geographical environment, the operation of the AAA appears less expensive than that of the older aircraft.

Thermoelastic characteristics testing on kevlar samples for spacecraft structures

Abstract The tensile properties, the thermal expansion coefficient and the thermal conductivity of woven roving (WR) reinforced Kevlar fabrics were experimentally determined. Theoretical values for tensile Youngs modulus were calculated by simulating a fabric as an equivalent cross-ply laminate. As thermal expansion coefficient concerns the fabrics have shown an isotropic behaviour. The thermal conductivity normal to fabric plane has also been determined.