Study On Preparation And Mechanical Properties Of PLA Composites Reinforced By Silk Woven Fabric

Natural fiber reinforced composite materials have become a hot research topic because of their good regenerability and biodegradability.Silk is a kind of natural animal fiber.The composite material prepared by the reinforcing body has good biocompatibility,light weight and high stress and strainability in addition to the characteristics of regenerability and biodegradability.Researchers at home and abroad usually use silk fiber or silk fibroin to prepare biocomposites,while there are relatively few studies on the preparation and mechanical properties of silk woven fabric reinforced biocomposites.Based on silk fiber reinforced polylactic acid composite material,with polylactic acid as the matrix,silk plain weave fabric as reinforcement,we optimized the process from three aspects(degumming with different alkali amount,proportion of different fabric quality and hot pressing forming parameters)and select the optimal compound condition.On this basis,three-dimensional woven fabrics of silk three-dimensional woven fabrics were prepared by weaving three kinds of silk three-dimensional woven fabrics,and the effects of three-dimensional woven fabrics on the mechanical properties of composites were studied.The research can provide some experimental references for the preparation of silk fabric reinforced composites,in order to provide new ideas for the development of silk composite materials.The main research contents and conclusions are as follows:(1)The mechanical properties of silk fabric reinforced composites were determined by testing different alkali dosages.The optimum alkali dosage was selected by scanning electron microscopy(SEM).The thermal properties of the composites were investigated by thermogravimetric analysis(TG).Studies have shown that when the mass fraction of alkali is 1%,the tensile properties and impact resistance of the composites are the best,reaching 48.58 MPa and 26.67 kJ/m~2 respectively,compared with the tensile properties and resistance of undebonded silk composites.The impact performance was enhanced by 51.38%and 84.70%respectively.At the same time,it was characterized by scanning electron microscopy(SEM)and thermogravimetric analysis(TG).It was found that after degumming with 1%alkali,the silk fiber and polylactic acid matrix were more tightly combined.The bonding performance was greatly improved,and it was found that the thermal properties of the composite after the degumming treatment were improved.(2)The effects of different silk fabric quality ratio on the mechanical properties of composites were studied by means of 3D video microscope and mechanical properties test.The orthogonal test method was used to select the L9(3~4)orthogonal table to enhance the polylactic acid composites of silk fabrics.The hot press forming process is optimized.The research shows that when the silk fabric has a mass ratio of 15%in the composite material,the mechanical properties reach the highest values of 51.85MPa and 42.46kJ/m~2,and the cross-sectional morphology of the composite material is analyzed by three-dimensional video microscope.At15%,a transition layer of a certain thickness can be formed between the silk fabric and the polylactic acid matrix,thereby effectively improving the mechanical properties of the silk-reinforced polylactic acid composite material.Using the range analysis method,combined with the composite surface and section morphology analysis,the optimal conditions for hot pressing were determined as follows:hot pressing temperature 165°C,hot pressing pressure 5MPa,hot pressing time 35 min.(3)Using low-twist silk yarn as raw material,three-dimensional orthogonal structure with the same number of layers,three-dimensional quasi-orthogonal structure,three-dimensional enhanced orthogonal angle interlocking structure,and symmetric joint with air gap are woven on ordinary small sample loom.Five kinds of three-dimensional woven fabrics with angular interlocking and inter-layer skew angle interlocking structure,tensile performance tests on five kinds of silk three-dimensional woven fabrics,followed by comparison of silk laminated plain woven fabrics and five different three-dimensional woven fabrics to enhance polylactic acid The mechanical properties of the composite.The results show that the mechanical properties of the three-dimensional woven fabric reinforced composites are higher than that of the same layer of plain woven composites,and the three-dimensional woven fabric reinforcement structure has a great influence on the mechanical properties of the composites.The interlaced state and the straightening state of the force direction yarn affect the tensile strength and impact resistance of the three-dimensional woven fabric reinforced composite material,wherein the three-dimensional orthogonal structure woven fabric reinforced composite material has the best tensile strength,and the symmetric connection with air interface The corner joint interlocking composite has the best impact resistance.