Preparation And Properties Of3D Cellular Composites Constructed By Ramie/Pla Co-Wrapped Yarn

Ramie fiber is one of the most common reinforced fibers of composites due to its advantages in light-weighted, strength and modulus etc. PLA filament finished its polymerization before impregnation, so the hot-pressing of composites is a physical process. Three-dimensional woven fabric is an ideal reinforcement structure with good integrity, relatively high in-plane mechanical properties, and outstanding damage tolerance.This project selected ramie as the reinforced fiber, PLA filament as resin system. Firstly, the co-wrapped yarns were prepared and three orthogonal fabrics were woven using co-wrapped yams. Then Cellular composites reinforced with three dimensional ramie fabrics woven with ramie/PLA co-wrapped yarns in different structures are successfully manufactured by compression molding.The co-wrapped yarns in this project are produced by wrapping PLA filament yarns around ramie core staple yarns in a fancy twisting machine, achieving more even resin distribution in the composite preform and thus better resin impregnation for3D thermoplastic composites. The research details are as follows:First of all, co-wrapped yarns with the PLA filaments distributing more uniformly on ramie staple yarn were produced by optimizing parameter and improving co-wrapping equipment.(1)6kinds of co-wrapped yarns were prepared with the output roller parameter being1.54Hz,1.74Hz,1.94Hz,2.14Hz,2.34Hz, and2.54Hz. The results showed that ramie staple yarn was co-wrapped evenly by PLA filament and had few uncovered parts when the parameter was2. MHz.(2) The results of ramie staple yarn were co-wrapped by PLA filaments in unidirectional and bidirectional showed that co-wrapped yarn in unidirectional could avoid the slippage of outer PLA filament as the result of lower friction. This method can reduce the warp and reed abrasion in weaving process. The warp properties of composites could be improved. (3) In this work, the yarn gather component was placed on the hollow spindle, which can which can achieve even resin distribution in the composite perform and thus better resin impregnation for composites. The yarn gather component could make the PLA filaments co-wrap ramie staple yarn in an angle of not less than60°.(4) Compared with the co-wrapped yarn with the single PLA filaments around ramie staple yarn, the PLA filaments with larger diameter could cover ramie staple yarn completely. This method could get higher resin content and reduce hairiness which was beneficial to weaving and impregnation of preform.Then, the plain woven fabric and three-dimensional orthogonal woven fabric were fabricated using the co-wrapped yarn which linear density is234.6tex. The weight ratio of ramie and PLA in this co-wrapped yarn is5.3to4.7. The composites were produced by hot-pressing. The results of mechanical test indicated the strength and modulus of tensile and flexural of3D orthogonal woven fabric reinforced composites were higher than2D laminated composites with close thickness, and the failure modes were also quite different. For the impact property in weft direction,3D orthogonal composites shower higher total absorbed energy and ductility index (DI). These results suggested that the cellular composites reinforced with3D woven fabric using ramie/PLA co-wrapped yarn were a good reinforcement structure.Finally, the weight content of PLA filaments for the co-wrapped yarns and warp yarn density for3D woven fabrics are varied to produce three kinds of light-weight composites with different fiber volume fractions and void content. The fiber volume content of three composite samples (C-1, C-2, C-3) is54.5%,47.5%,45.6%respectively. And the porosity increased with the larger of co-wrapped yarn diameter, is17.2%,20.9%,22.4%corresponding to the fiber volume content. The results of surface morphology and internal structure of3D composites samples showed that there were Z-yarn distortion in all the samples although the integrity of3D composite was still maintained, the sample with the highest resin content was found the best resin impregnation. The results of mechanical properties test showed that the tensile strength and Young’s modulus of the composite samples C-1, C-2and C-3increased with the increasing void content and decreasing fiber volume fraction. The sample which fiber content is45.6%had the best tensile and impact properties, attributed to the fact that cellular composites reinforced with three-dimensional orthogonal woven fabric using ramie/PLA co-wrapped yarn had good mechanical properties, and was light-weighted. And the cellular PLA composites reinforced with ramie woven fabric have good sound absorb property in the low frequency range.This research work can provide an important experimental thesis for the development of composites which is environmentally, light-weighted and high-strength.