R E S E A R C H

P o l y m e r C o m p o s i t e s :

It is generally recognized that the bond strength variation at the fiber/matrix interfaces greatly affects the mechanical characteristics of composite materials. Due to their anisotropic nature and complicated architecture, it is very difficult to reveal the damage mechanism of these materials. Fiber composite materials are becoming an essential element in major technologies. Thus, an accurate evolution of their mechanical as well as chemical characteristics becomes very important, especially if they are used under various loading conditions and also at above- and sub-ambient temperatures. The benefits of light-weight polymer matrix composite components to aircraft engines are well known. Although thousands of polymer composite components are currently in service, barriers still exist to further implementation in more structurally critical and at different temperature applications. Most of these barriers are associated with the inability to accurately predict component lives, and therefore, component life-cycles costs. A fiber reinforced composite materials with a polymer matrix is highly susceptible to damage by environmental parameters, like, moisture, high and cryogenic temperatures, UV radiation, and thermal shocks etc. Most polymers are also loading rate sensitive. A change in loading rate may result in variation of failure modes. Many theories point out the complexity of the phenomena that manifest at the fiber/matrix interface or interphase. The predominant failure mechanisms in a composite laminate are a very complex combination of energy absorption mechanism such as delamination mainly caused by mode II shear, matrix cracking due to transeverse shear, and translaminar fracture in terms of fiber fracture and kinking. The interfacial area is dependent on the processing conditions,which are generally chemical, mechanical, and thermo-mechanical in nature. These may introduce spatial non-uniformity of properties at the fiber/polymer interface. Little, if any, literature regarding the effects of strain rate on the damage behaviour of environmentally aged FRP composites at different temperatures has been published to date. An interfacial reaction may further impart various morphological modifications to the matrix microstructure in proximity to the fiber surface. A great need exists for a critical assessment of micro-characterization of polymer composites at different temperatures and loading conditions. Weight change behavior of fiber-reinforced polymer composites in humid and thermal environments appears to be a complex phenomena. The state of fiber/matrix interface is believed to influence the nature of diffusion modes. A significant weakening often appears at the interface during the hygrothermal ageing. It effects the moisture uptake kinetics and also the reduction of mechanical properties. The importance of temperature at the time of conditioning plays an important role in environmental degradation of such composite materials. The hygrothermal conditioning impairs the fibre/matrix interfacial and/or interphasial chemistry, which plays a predominantly important role in determining the mechanical properties, especially the matrix dominated one, of a polymer composite.

The Institute has facilities like, Instron Tensile Testing Machine, Cryogenic and other environmental chambers, UV chambers, DSC, SEM to carry out the work. Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR) Imagining techniques will certainly be meaningful and effective additions to perform critical and micro-characterization of very small interactions and chemical structural gradient at the interphase of polymer composites. The focus area of our research aims at assessing and correlating the influence of structural gradient at the fibre/polymer interface on mechanical behaviour of advanced and hybrid composites, consisting synthetic and natural fibers.

M e t a l M a t r i x C o m p o s i t e s :

Metal matrix composites (MMCs) combine both metallic properties (ductility and toughness) with ceramic properties (high strength and modulus) possess greater strength in shear and compression and high service temperature capabilities. The extensive use of MMCs in aerospace, automotive industries and in structural applications has increased over past 20 years due to the availability of inexpensive reinforcements and cost effective processing routes which give rise to reproducible properties. The frontier zone between the matrix and reinforcement phase (interface or interphase) is an essential part of MMC. Bonding between the two phases develops from interfacial frictional stress, physical and chemical interaction and thermal stresses due to mismatch in the coefficients of thermal expansion of the matrix and reinforcement. During the design of a MMC the underlying interfacial phenomenon which governs the transmission of thermal, electrical and mechanical properties is of utmost importance . In general, there are two processing routes to incorporate ceramic particulates into the metal matrices. Introduction of ceramic particulates into the matrices of MMCs via ingot casting or powder metallurgy (PM) processes are most popular. The ceramic particulates are synthesized separately prior to the composite fabrication. Such composites are termed as ‘ex situ’ MMCs in which agglomeration of fine ceramic particulates often occurs during processing. The in-situ route provides several distinct advantages over conventional ex situ process, e.g. in situ formed reinforcements are more uniformly distributed, finer in size, and thermodynamically stable leading to superior mechanical properties compared to their ex situ counterparts. Conversely, the powder metallurgy route in case of oxide reinforcements has an added advantage as they follow the energy efficient method. The greatest threat in this fabrication route is the absence of an integrated interface formation as the metal powders are less reactive in solid state. The fabrication and micro-characterization of the interface gives way to correlation of processing parameters to the interfacial characteristics.

P h a s e T r a n s f o r m a t i o n & H e a t T r e a t m e n t :

The isothermal transformation kinetics was analysed in terms of Avrami Equation. The mathematical modelling was formulated to predict the progress of Austenite-to-pearlite transformation during continuous cooling. The kinetics is characterized by subdividing the cooling curve into a series of isothermal steps. The need to develop such computer model is that steel industries are rapidly adopting continuous processes includes continuous casting, continuous heat treatments to minimize process cost and to improve quality of the products. The findings revealed that there is a close proximity and a reasonably good agreement between calculated and experimental data.