Natural fibres will take a major role in the emerging "green" economy based on energy efficiency, the use of renewable materials in polymer products, industrial processes that reduce carbon emissions and recyclable materials that minimize waste. Natural fibres are a kind of renewable resources, which have been renewed by nature and human ingenuity for thousands of years. They are also carbon neutral; they absorb the equal amount of carbon dioxide they produce. These fibers are completely renewable, environmental friendly, high specific strength, non-abrasive, low cost, and bio-degradability. Due to these characteristics, natural fibers have recently become attractive to researchers and scientists as an alternative method for fibers reinforced composites. This review paper summarized the history of natural fibers and its applications. Also, this paper focused on different properties of natural fibers (such as hemp, jute, bamboo and sisal) and its applications which were used to substitute glass fiber.

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Natural fiber reinforced composites are progressively used in a variety of commercial applications such as automotive, aerospace and marine. Many technologies demand materials with unusual mixture of properties such as high strength to weight ratio, high stiffness, high corrosion resistance, high fatigue strength, high dimensional stability, etc. These can't be met by conventional metal alloys, due to comparable properties the scope of for natural fibers became enormous. More research work is done on natural fiber composites. But, woven jute fiber and epoxy resin matrix is not used for research studies. Literature review shows that composite made of combination of these constituents is not studied in order to know its properties. Present study focus on the effect of nano silicon dioxide as filler on tensile, flexural and fatigue properties of jute reinforced epoxy composites with three different combinations of filler material and two different orientations. The three different compositions were 0 % nano silicon dioxide, 5 % nano silicon dioxide, 10 % nano silicon dioxide. The two different orientations were 0/90 and +45/-45 orientation. Tensile and flexural strength of all the compositions of the composites reveled that ultimate tensile strength, peak load and young's modulus were more in case of 5 % silica filled jute epoxy composite compared to other two compositions. Similarly fatigue test to determine the number of cycles up to 50 % stiffness degradation of laminates reveals that specimens loaded with 5 % nano silicon dioxide shows higher number of cycles. The study concludes that the combination of filler and fiber composite material is competitive to synthetic composites.

The growth in practical applications of sandwich constructions in high performance vehicles, aerospace, marine, automobile, and electronic packaging industries needs a thorough investigation of all vibration modes of the structure. This is to ensure that debonding between facings and core in the through-thickness vibration mode does not occur during service. In the present work, experimental modal analysis on sandwich panels of different densities and core thicknesses have been carried out under three different boundary conditions. The influence of rigid inserts of different volume fractions on the dynamic behavior has also been examined. A non-dimensional parameter representing the ratio of core density and core thickness to face density and face thickness has been established, which correlates excellently with measured fundamental natural frequency. The corresponding mode shapes and modal damping have also been evaluated.

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