Liquid composite molding (LCM) processes are widely used to manufacture composite parts for the automotive industry. An appropriate selection of the materials and proper optimization of the manufacturing parameters are keys to produce parts with improved mechanical properties. This paper reports on a study of biobased composites reinforced with nanoclay particles. A soy-based unsaturated polyester resin was used as synthetic matrix, and glass and flax fiber fabrics were used as reinforcement. This paper aims to improve mechanical and flammability properties of reinforced composites by introducing nanoclay particles in the unsaturated polyester resin. Four different mixing techniques were investigated to improve the dispersion of nanoclay particles in the bioresin in order to obtain intercalated or exfoliated structures. An experimental study was carried out to define the adequate parameter combinations between vacuum pressure, filling time, and resin viscosity. Two manufacturing methods were investigated and compared: RTM and SCRIMP. Mechanical properties, such as flexural modulus and ultimate strength, were evaluated and compared for conventional glass fiber composites (GFC) and flax fiber biocomposites (GFBiores-C). Finally, smoke density analysis was performed to demonstrate the effects and advantages of using an environment-friendly resin combined with nanoclay particles. 1. Introduction Recent advances in the composites field are related to the addition of nanoparticles such as carbon nanotubes, nanoclays, or silicates nanoparticles to improve the thermal, mechanical, and electrical properties. Nanoparticle additives, like nanoclay, are widely used in various industries such as cable coatings, adhesives, inks, pharmaceutical and automotive [1, 2]. One of the most common nanoclay forms is montmorillonite (MMT) with a particle thickness of 1？nm and 70 to 100？nm crosswise silica platelets [3, 4]. The choice and extensive use of montmorillonite nanoparticles in previous research is mainly due to the fact that they are commonly available and inexpensive [5]. Minimal content (1–5%？wt) of such additives can improve the reinforcement of the polymer matrix by increasing flexural modulus by up to 31% and lowering the coefficient of linear thermal expansion [6–8]. However, the incorporation of nanoparticles into the liquid matrix is still a challenge, because it requires proper dispersion and exfoliation of the nanoclay. Since they are hydrophilic in their natural state and unevenly distributed, they must be organically modified to avoid agglomeration between
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