Srikanth Vedantam

Resin Film Infusion (RFI) process is used for manufacturing large and thick unidirectional fiber reinforced polymer (UD FRP) composite structures for load bearing applications. Designing these load bearing structures requires the knowledge of effective elastic and strength characteristics of these composites. In this study, strength and stiffness properties of UD FRP manufactured through RFI process are predicted using a micromechanical modeling approach. A 3D representative volume element (3DRVE) with hexagonal array of fibers is used and all nine elastic constants of UD FRP composite are predicted. Failure models for fiber and resin are used to predict longitudinal tension/compression, transverse tension/compression and longitudinal shear strengths. Experiments were conducted on UD FRP composite manufactured through RFI process to obtain strength and stiffness properties. Results of experiment and simulations are compared and results validated.

Fibre-reinforced composite materials offer a number of distinct advantages such as higher specific strengths and stiffness over more conventional engineering materials such as aluminum or steel. When loaded in the fibre direction, these materials are the best choices in the modern world, but they do suffer severe limitations when undergoing impact loadings such as dropped tool or runway debris. To design a composite material that can offer solutions to the problems discussed above is important. Thus in this paper, our aim is to introduce a highly ductile, energy dissipating shape memory alloy (SMA) wire inside a composite material as a fibre that exhibits pseudoelastic response. To predict the behaviour of the SMA composite, as SMA is a non-linear hysteretic material, we have developed an incremental SMA composite model using the Voigt method.

Due to their high strength to weight and stiffness to weight ratio, there is a huge shift towards the composite materials from the conventional metals, but composites have poor damage resistance in the transverse direction. Undergoing impact loads, they can fail in wide variety of modes which severely reduces the structural integrity of the component. This paper deals with the homogenization of glass-fibers and epoxy composite with a material introduced as an inelastic inclusion. This nonlinearity is being modelled by kinematic hardening procedure and homogenization is done by one of the mean field homogenization technique known as Mori-Tanaka method. The homogenization process consider two phases, one is the matrix and another is the inelastic inclusion, thus glass-fibers and epoxy are two phases which can be considered as one phase and act as a matrix while homogenizing non-linear composite. Homogenization results have been compared to the matrix at volume fraction zero of the inelastic inclusions and to the inelastic material at volume fraction one. After homogenization, increase of the energy dissipation into the composite due to addition of inelastic material and effects onto the same by changing the properties of the matrix material have been discussed.

Present work deals with the analysis of the variation in the stresses of an inelastic composite cantilever beam. The cantilever beam is made up of four bi-directional symmetrically stacked glass-fiber/epoxy (GFRP) laminas. The stress field in the beam has been calculated using one dimensional finite element formulation of the Timoshenko beam theory. GFRP are the elastic composites and their behaviour is brittle. Thus the energy dissipation is generally given by the area under the elastic curve. The addition of the inelastic fibers in the composite extend this area after the yield stress leading to the more energy dissipation. To achieve an increase in the energy dissipation, aluminium (Al.) has been introduced as an inelastic fiber in the top-most layer and is considered to undergo kinematic hardening. Finite element formulation has been done for the aluminium reinforced glass fiber/epoxy composite cantilever beam. At small loads, even an incremental increase in the plastic area can be beneficial. The overall stiffness of the top-most layer is calculated by the rules of mixtures (Voigt) method and updated once stresses reach in the inelastic zone. As the top and the bottom most layer is made up of same composite material but the only difference is that of inelastic fibers in the top most layer, we can compare the stresses and how much energy dissipation increases in the top-most layer. The effect of varying the thickness on the stresses and energy dissipation is discussed.