The Preparation And Properties Of Continuous Fiber Reinforced PA6composites

Thermoplastic composites have been successfully used in aerospace, transportation, electronics, building materials and other fields due to their high toughness, good impact resistance, short molding cycle, excellent chemical resistance and repeatableprocessing. Because of the high meltviscosity of the thermoplastic resin, the critical points of preparation of the thermoplastic composites are the impregnation problems.In this paper, the glass fiber and PA6fiber were evenly mixed into a bundle of fibers for better impregnation. Firstly, the fiber bundle was knitted to apreform,then the preform was heated under a certain pressure to form a prepreg. With a certain plies design, the prepreg were heated again in a certain pressure to form composite laminates. The molding parameters (pressure, temperature, time), crystallization kinetics andheat treatment process were studied.The research provides a new approach and theoretical guidance for the preparation of the thermoplastic composite laminates.This dissertation addresses the following work:1. Orthogonal experimental method was usedto explore the influence of pressing temperature, pressure, time on mechanical properties of composite laminates, fixing the optimal hot pressing process parameters as follows:temperature250℃, hot pressure3.5MPa, pressing time10min. Composite laminates exhibit optimal mechanical properties under this condition:tensile strength, tensile modulus are476MPa,20.61GPa respectively, flexural strength is445MPa and flexural modulus is16.37GPa, interlaminar shear strength is25.66MPa. PA6resin and fibers havea good impregnation under this processing condition by fracture morphology analysisof the samples.2. Non-isothermal crystallization behavior of pure PA6resin composites and GF/PA6were analyzed by using differential scanning calorimetry (DSC). The crystallization exotherm of PA6and GF/PA6composites were analyzed. It is found that with the cooling rate increases, the crystallization starting point and crystallization peak moved to the low temperature, crystallization peak broadened, crystallinity degree of perfection lower. The crystallization starting temperature improved by adding fiber and this implied that the fibers contribute to the generation of crystal nucleus; but the peak temperature, the crystallization enthalpy of GF/PA6were lower than pure PA6, indicating that the addition of fiber hinder the movement of the polymer molecular chain, affecting the crystallization and eventually reduced the crystallization degree of GF/PA6. Avrami, Ozwa, Mo methods were used to simulate the non-isothermal crystallization kinetics of GF/PA6and found that Avami, Mo equation could describe their non-isothermal crystallization kinetics behavior.3. The composites wereannealed at180℃under vacuum to study the effect of heat time on GF/PA6composite properties. The results show that crystallinity ratio of PA6in the composite samples increases10%after10h heat-treatedcompared tothe untreated samples, makingflexural strength and shear strength of the specimen increase18%and20%respectively.