My research area is in polymer based composite materials. Currently focus has been placed on the investigation of polymeric fiber reinforced functionally gradient materials. The concept of functionally gradient material (FGMs) was proposed in 1984 by Japanese materials scientists as a means of preparing thermal barrier materials. Since then, this concept is accepted worldwide as it can be applied to various material fields for structural and functional uses. The functionally gradient materials are characterized by non-linear 3D-distribution of phases and corresponding properties. The composition and structure of a functionally gradient material varies in a specified manner with position in the material. A consequence of the gradient composition and structure is that there is also a controlled change in the properties of the FGM with position. They are distinguished from isotropic materials by gradients of composition, phase distribution, porosity, texture, and related properties (fiber architecture for the case of polymeric fiber reinforced FGMs). Generally, functionally gradient material can be classified into three main categories which may be termed interface, surface and bulk FGMs. Of these categories the interface FGMs are the nearest to full commercial exploitation. The two main projects in Japan involve the development of functionally gradient materials for relaxation of thermal stress and research on energy conversion materials with functionally gradient structure. The former project has already gains significant success with the successful fabrication of FGMs with powder metallurgy, plasma spraying, CVD and SHS techniques.
Most of the current researches are focused on metal-ceramic composite and the use of FGMs in bio-medical application is limited. However the potential of FGMs being used as a bio-medical material is promising. Biomaterials must simultaneously satisfy many requirements and possess properties such as non-toxicity, corrosion resistance, thermal conductivity, strength, fatigue durability, biocompatibility, and sometime aesthetics. Taking dental implant as an example, not only it has to withstand tremendous tensile, compressive and torsional loads induced during occlusion. It must also be able to resist the corrosive environment, thermal stressed subjected to it and be bio-compatible to our body. Conventional material, which usually consists of single composition with uniform structure, cannot satisfy all these requirements. Natural biomaterials often possess the structure of functionally gradient materials (FGM) which enables them to satisfy these requirements. For example human teeth are made up of various tissues, mainly enamel and dentine. The dentine is a form of mineralized tissue whereby there is a distribution of the organic matrix and mineral throughout the entire structure. Compact bone has also similar distribution, which give rise to variation in properties within the structure. FGMs provide the structure with which synthetic biomaterials should essentially be formed.
The use of fiber reinforced polymeric composite as a functionally gradient material is currently look into in our researches in polymer and textile composite department of Material Science Division in National University of Singapore. Current research areas here include fabricating FGMs using braided fiber preform as the backbone of the FGMs, modeling the fabricated FGMs and characterization of the properties of the fiber reinforced polymeric FGMs. The intended application of this FGM is to use it as dental post system in dental application. If the current research is successful, stress concentration problem in conventional metallic dental post system will be eliminated and will facilitate better load transfer from the crown region of the restoration to the root of the restored tooth. No doubt, these will improve the functional properties of the dental post and prolong its life span and prevent premature failure of the tooth restoration.