The use of composite materials has seen many new innovations for a large variety of applications. The area of reinforcement in composites is also rapidly evolving with many new discoveries, including the use of hybrid fibers, sustainable materials, and nanocellulose. In this review, studies on hybrid fiber reinforcement, the use of nanocellulose, the use of nanocellulose in hybrid forms, the use of nanocellulose with other nanomaterials, the applications of these materials, and finally, the challenges and opportunities (including safety issues) of their use are thoroughly discussed. This review will point out new prospects for the composite materials world, enabling the use of nano- and micron-sized materials together and creating value-added products at the industrial scale. Furthermore, the use of hybrid structures consisting of two different nano-materials creates many novel solutions for applications in electronics and sensors.

Reinforcing natural fibers to polymer matrices provides an increase in mechanical properties. In addition, bio composite materials contribute to the sustainable ecosystem with its ease of recyclability. The effect of accelerated aging on the mechanical properties of PLA matrix bio composite specimens has been observed in previous research, but the effect of accelerated aging on the mechanical properties and the resulting mass loss of the material produced with fused filament fabrication (FFF) has been discussed for the first time in this study. Aging was applied to the bio composite consisted of 10% hemp and PLA matrix produced at a constant rate, parallel to the tensile direction and cross (+/– 45°) angle, and the results were examined as tensile stress and mass loss. The aging effect has been observed even from the first week. Specimens with parallel printing to tensile direction showed a lower tensile performance than cross printing one, since the structure in the laminates is quite durable, the adhesion performance in the laminate or through thickness direction has been low. Natural fibers are found so highly hygroscopic that chemical treatments will improve the interface and increase the mechanical properties.

Reinforcement of polymer matrix with natural fiber can provide an increase in mechanical properties of the related composite. Since thermoplastics, especially bio composite materials are recyclable, they contribute to a sustainable ecosystem. In this study, 10% by weight hemp reinforced polylactic acid (PLA) matrix compounds were produced. Tensile test specimens were performed in two different infill patterns, parallel and +/- 45° cross, using the Fused Filament Fabrication (FFF) method from the developed bio composite filaments. Ultimate tensile stress increases approximately 20%. It has been observed that the geometry of the infill pattern greatly affects the tensile strength. In addition, through optical and scanning electron microscopy (SEM) the the produced composite filaments were examined. Surface interactions and homogeneous fiber distribution between PLA and hemp were investigated. As a result, hemp is used as a reinforcement material in related studies, its homogeneous distribution is very important. Although the compounds were produced by twin-screw extrusion. Weakness in the form of the surface bonding is observed. This situation affects the structural performance negatively. Addition of hemp decreases the thermal resistance and melting temperature and increases the glass transition temperature comparing to pure PLA.

In today's modern world, composite materials play a crucial role in various areas. But still, the main important application of the composite materials is in the transportation industry; in automotive, aerospace, and marine applications. With recent concerns about CO₂ emissions, the use of high specific strength materials has become more and more important and this chapter deals with the recent trends in the developments in the composite materials that are used in the transportation sector. We believe that this important book on recent technologies in composite materials will open many dimensions for people and this chapter in the book will highlight the recent innovations in the composite industry for the transportation industry. The sailing boats and motorboats have become fancier with the recent developments in the composites. The automotive is having a revolution by being converted to electrical cars and there is a great demand to reduce the weight of the cars with composite chassis materials. The airplanes can now fly much faster with the developments in the composites. We have summarized all these findings in this chapter. We hope it can be helpful for the reader.

In recent years, there has been an outbreak of research on natural fiber-reinforced materials to reduce non-recycled material effects and produce environmentally friendly products. In parallel with the increasing popularity of additive manufacturing, the development of new natural fiber-reinforced materials in this field has also increased to improve pure material characteristics and reduce raw materials usage. This study presents the manufacturing process of %5 waste jute-reinforced PLA filaments and the characteristics of 3D printed parts. For the production of jute-reinforced filaments, polylactic acid (PLA) granules were pulverized to increase the material surface for better bonding between materials in the composite matrix structure. The effectiveness of pulverizing PLA granules was exposed by comparing it with the production of the same composite matrix with PLA granules. Both matrices were formed into filaments to produce 3D parts in Fused Filament Fabrication technology. Thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) will be presented in filament form. Besides, the mechanical properties of 3D parts will also be presented. Within the scope of the study, it is aimed to reveal the material size effect for producing natural fiber-reinforced filaments for additive manufacturing.