Moisture and Flammability Behaviour of flax Fibre and Natural Fillers-Based Hybrid Epoxy Composites Sudhir Kumar Chaudhary , Hitesh Sharma , and Gaurav Kumar 1 Introduction Two or more different materials with different physical and chemical properties are combined to form a new material which possesses properties entirely different from main constituents are acknowledged as composite materials. There has been striking growth of composites as they provide the materials with stiffness and tough- ness. The biggest advantage associated with composites is that their properties can be customized and manipulated. Natural fibre-based composite has been used in the fabrication of aircraft parts, submarine structure, production of sports good and medical instruments [1, 2]. Natural fibre-based composites found its uses in many applications. However, they are still vulnerable to fire and moisture and limited studies have been reported. As they found their application in aircraft parts, construc- tion works, hence, the risk of catching fire can be dangerous [3]. However, natural fillers-based composites have found their various applications against the synthetic fillers-based composites as they are abundant in nature and relatively low cost associ- ated with them. Several properties of the natural fibre-based composite are superior to those of glass fibre-based composite [4]. Initially, these composites are used in indoor application as they are very vulnerable to moisture and fire, but as more research has been done on these natural fibres-based composites, they have also found their use in outdoor applications. Different types of parts are manufactured using natural fibres without compromising the mechanical strength of the material. Natural filler and fibre-based composites are also seen as alternatives for synthetic materials as they do less harm to nature and easily biodegradable as compared with those of synthetic composite. S. K. Chaudhary (B ) · H. Sharma · G. Kumar Department of Mechanical Engineering, National Institute of Technology Uttarakhand, Srinagar Garhwal 246174, India e-mail: sudhir.mechmt18@nituk.ac.in © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 P. K. Rakesh et al. (eds.), Advances in Engineering Design, Lecture Notes in Mechanical Engineering, https://doi.org/10.1007/978-981-33-4018-3_36 385