Polymer hybrid composites are materials which are made by combining two or more different types of fillers in a common polymer matrix. Hybrid materials are one of the fastest developing classes of new materials and have led to numerous technological innovations. Reinforcement by two or more fillers (natural/natural, natural/synthetic, and micro/nano) in a single matrix leads to hybrid composites with a great diversity of material properties. Hybridization of two different fibers has proved to be an effective method to design materials suited for various requirements.

Incorporation of fibers (natural/synthetic, micro/nano) into a polymer is known to cause substantial changes in the physical and mechanical properties of composites, and in some cases the strength of the hybrid exceeds the rule of mixtures (synergistic strengthening). The combination of the unique properties that emerge as a consequence of the particular arrangement and interactions between the different constituents provides immense opportunities for advanced material technologies. The concept of hybridization provides flexibility for the design engineer to tailor the material properties according to the requirements, which is one of the major advantages of the composite materials.

The aim of this special issue is to present the latest original research and review articles in all areas of natural/synthetic fiber based hybrid composites, focusing on novel experimental techniques for their preparation and developed theories for predicting their different properties. This special issue will aim to provide a more detailed understanding of the relationship between synthesis, structure, characterization, processing, applications, and performance of these advanced materials.

Potential topics include but are not limited to the following:

• Natural/synthetic fiber hybrid composites
• Natural/synthetic fiber hybrid nanocomposites
• Additives in hybrid polymer composites
• Green hybrid polymer composites
• Natural/synthetic fiber hybrid composites applications
• Novel techniques of processing and fabricating various types of natural/synthetic fiber hybrid polymer composites
• Testing and characterization of natural/synthetic fiber hybrid polymer composites
• Mechanics theory of hybrid polymer composites
• Modelling and simulation of hybrid polymer composites
• Future directions for developing hybrid polymer composites