Development of Nano Technologies

Development of Nano Technologies Introduction Extensive work has been put into the research of nanotechnology capabilities in the past decade and the findings have opened a new range of multi-functional materials in the industry. However, a major issue faced today is incorporating nano-particles into the final composite structure by using current infrastructure. New developments in the field, such as multifunctional materials with enhanced electrical, thermal and mechanical properties are required by several industrial applications. This review is an attempt at showing the most recent and representative performances of nano-enabling technologies reported in literature. The focus of this review is on the two main manufacturing technologies used in aerospace industry: Autoclave (or Pre-preg pre-impregnated composite fibres), and Resin Transfer Moulding (RTM) technologies. It looks at several approaches used in the nano-enabling of composites for the aforementioned paths and presents the latest reported results from literature. Fi nally, this work shows the difference between available integration nano-technology and future developments that are currently in demand for aerospace applications. Since the early 90s, micro- and nano-phase in polymers have been successful ways to improve material performance in various structural (such as strength, stiffness, energy absorption and thermal stability) and non-structural functionalities (such as thermal conductivity, energy storage and structural health monitoring). There are mainly two routes to creating nano-enabled composites nano-augmentation (random and homogenous distribution of nano-particles in the material) and nano-engineering (pre-organized distribution of nano-particles) [5]. These methods are considered the most promising in regards to multi-functionality increased performance and integrating possibilities. [6]Such materials, also called hierarchical composites may gain new properties from nano-scale incorporation as well as benefiting from the advantages of traditional structural (Fig. 2). Since the early 00s, significant economical efforts have been invested in the research of such innovative materials. The aeros pace industry has been a leader in this development, requiring high performance materials with high durability to extreme environment conditions. Fibre reinforced composites are used in applications such as structural panels, satellite platform and solar array substrates. These applications can improve through nanotechnology with development in permeability for cryogenic tanks and durability to diffusion species, space station oxidation resistance, mechanical toughness against structure damage, high modulus for stable and precision structures, interlaminar shear strength for tubular structures, electrical conductivity for electrical dissipation and lightning strike protection, etc.[8]. In this review, nano-enabling of composites methods are presented from the processing and manufacturing point of view. The works perspective is focused on near term application. Firstly, all the steps of each technique are identified, and then the options available for nano-scale phase integration are evaluated. The evolving trends are presented alongside through reported performance of novel composite material systems. Lastly, the expected near and long-term progress is reviewed. Main Body This review focuses on the two most commonly used technologies Autoclave/ Prepreg and RTM. Prepreg technology is currently most used in aerospace industry for manufacturing high performance components while the latter is used as an alternative for large complex shapes. The differences between the two techniques can be observed in the state of the fibre reinforcement (dry or wet) and the curing methods (autoclave i.e. heating in a container, or out-of-autoclave curing). Most of the space structures are assembled from prepreg systems, which are set up on moulds and cured in an autoclave [3]. With RTM, the fibre that forms in dry state is preassembled to form the preform reinforcement and it is used for complex shapes that can be more readily made than other moulding techniques. With these methods covered, it is thought that the majority of composite production technologies for aerospace industry are addressed. Pre-impregnated composite manufacturing route This method is considered the most entrusted for producing high performance aerospace structures. Prepregs are very flexible, being able to cover various material needs given proper selection of the matrix and the fibre. Currently, due to the well-established prepregs, autoclave and automated laminating manufacturing industries, it is crucial to find methods that allow the incorporation of nanotechnology in prepregs without changing already developed steps in composite manufacturing. The conventional process for Autoclave Cured Prepreg Composite Manufacturing is mapped in Fig. 3. The process starts with the preparation of the available materials which are then manually or automatically laid-up with the required layers cut to the shape and size from the roll, based on the composite component requirements. Vacuum, combined with high temperature and pressure is used to assist a controlled resin flow in the elimination of entrapped air until the final cure of the part. Afterwards, when t he temperature and pressure are brought to ambient levels, the part is demolded and tempering and finishing is applied. In some cases (for example high performance polymers), a post-curing cycle may be required. Resin transfer molding composite manufacturing route RTM can be used to describe various techniques in aerospace industry [10, 11], such as Vacuum Assisted RTM (VARTM) and Resin Film Infusion (RFI). Generally, RTM is a process that belongs to out-of-autoclave manufacturing, where liquid resin is injected in a dry fibrous enclosed preform until the final curing of the part. RTM is a cost effective process when the component production numbers are high (