Flax Fiber / Low Melting Point Polyester Non-woven Preform Reinforced Composites Research

In this research , the method of compression moulding flax reinforced low melt point PET (LMPET) composite and the properties of composites are studied. The preforming is in the form of nonwovens.Fiber content decides the modulus and strength of composites, so in the study the different ratio of blending of flax and LMPET are combed to webs and manufactured into composites. The results shows that composites, which the wt% of flax range around 40%, have better mechanical properties. Because of the differences between longitudinal direction and transversal direction in nonwovens, the strength in the longitudinal direction exceeds the strength in the transversal direction. The laminated composite are manufactured and analyzed, the results show longitudinal tensile strength in laminated composite increases by 40% according to that in transversal direction, and decreases 46% according to that in longitudinal direction, also flexural strength in laminated composite increases by 50% according to that in transversal direction, and decreases 10% according to that in longitudinal direction. Flat carding machine has higher strength producuts than roller carding machineThe moulding parameters have great affluences on properties of composites. The research shows that the higher moulding pressure accompanies by more densified composites and larger strength. And in this paper the moulding pressure is 9MPa Composites have larger tensile strength and flexural strength when the moulding temperature is about 180℃ and moulding time is around 30 minutes. It is also founded that the longitudinal mechanical properties drop when the preforming are preheated. The reason is the curving of LMPET fibers when they are heated.The interface between flax fiber and LMPET is very important to the properties of composites. The results show having been treated by alkali the cohesion between the flax and LMPET is improved. The longitudinal tensile strength increases by 10% and the longitudinal bending strength increases by 22%, the lateral tensile strength increases by 2% and lateral bending strength increases by 14%. Accordingly the impact resistance drops and rigidity improves. The SEM is used to analyze the effectof alkali treating.The moulding ability and properties of complex composites are also discussed. The mould is devised and manufactured, which is used to mould complex composites. The research shows this method has many advantages, such as less moulding time, easy to mould, suit for large scale production and complex composite.