**6. Conclusion**

The natural fiber polymer composites have gained a lot of ground in terms of acceptance and applications. For these interests to increase continuously, the materials must be designed to meet certain requirements for their specific applicability. For structural applications, the most important property that is of concern is the mechanical properties as they help to predict the behavior of the materials under stress. As discussed in this chapter, NFPCs are being applied in the building and construction works, automobiles, aerospace, packaging, electronics and biomedical devices. The mechanical strength and toughness require by these various industries are quite different and can vary widely from one application to another. Even though the mechanical requirement varies, the factors that determine the mechanical properties are the same. These factors include type of fibers used, source of the fibers, surface treatment and modification carried out on the fibers, type of polymer matrix used (pristine and blended), type of fiber-matrix bond formed, and the internal arrangement which depends on the type of curing treatment after processing or annealing. In addition to this list are the fiber length, fiber orientation and distribution, fiber loading or volume faction, the type of functionality present and the extent of modification. All these factors can be manipulated to give a combination of the right measure of mechanical strength and stiffness or toughness required for the application it is being designed for. The use of compatibilizers and nanoparticles to modify the composites for specific purpose has been widely reported to improve the mechanical properties as well, but proper integrations must be considered. Furthermore, the use of hybrid fibers has also gained wide acceptance because of the improved stiffness and strength owing to the synergy observed in such fiber combination. The possibilities of NFPCs can be best imagined with the right improvement in their mechanical properties and this chapter has highlighted some of these benefits as presented by numerous research investigations across diverse fields.
