Modeling the Processing of Natural Fiber Composites Made Using Liquid Composite Molding

Abstract

Natural fi bers are being used increasingly to substitute artifi cial glass and carbon fi bers in polymer composites. Liquid Composite Molding (LCM) processes are an important set of “liquid molding” technologies to manufacture net-shaped composites parts that involve fi lling a dry, fi ber-packed mold with a thermosetting resin. However, not much is known about the fl ow of resins, bio-resins and test liquids through a preform made from natural fi bers. The swelling of natural fi bers due to liquid absorption adds a new dimension to the conventional mold-fi lling simulation in LCM conducted to optimize mold-design. Unlike the glass or carbon fi ber mats, the swelling of natural fi bers causes the permeability and porosity of the LCM fi ber mats to reduce with time during the mold-fi lling process. This chapter presents some recent developments in the science of LCM fl ow-modeling with natural fi bers used as reinforcements. Some studies on measuring the permeability of naturalfi ber preforms using the conventional LCM fl ow model using organic and inorganic test liquids are presented fi rst. Later some recent attempts to include the swelling and absorption into the LCM fl ow physics are also discussed where some analytical solutions for simple 1-D fl ows under constant pressure and constant fl ow-rate conditions are discussed. Some recent approaches to numerically simulate the LCM mold-fi lling type processes in swelling, natural-fi ber based materials are presented.