Fabrication And Characterization Of Natural Cellulose Fabric/Epoxy Composites And Their Application In National Percussion Instruments

The unique mechanical and acoustical properties of wood make it the material of choice for national percussion instruments.However,in recent years,for musical instruments,due to the requirement of environmental protection and depletion of wood recourses,availability of wood is no longer sustainable.Besides,wood could be rotten and is easily deformable by changes of temperature and humidity,which could affect the sound quality and reassembly of the instrument as well as its service life.Ordinary polymeric materials are not a suitable alternative because their acoustic properties are not close to those of wood.Therefore,it is necessary to find new alternative materials for national percussion instruments.Natural cellulose fibers such as ramie,jute,flax and hemp,are composed of mostly cellulose with much better mechanical properties than wood.Natural cellulose fiber reinforced polymer matrix composites are not only light-weight,environmentally friendly,biodegradable,and regeneratable but also have excellent and tailorable mechanical properties,making them an ideal alternative for national percussion instruments.In this work,four different natural cellulose plain woven fabrics were employed to reinforce epoxy composites.In order to alter interfacial properties between the fibers and the matrix,the natural cellulose fabrics were all alkali-treated with Na OH solutions.Natural cellulose fabric/epoxy composites were prepared by vacuum assisted resin transfer molding(VARTM).The tensile and flexural properties of the four natural cellulose fabric/epoxy composites before and after the alkali treatment were tested and analyzed.The acoustic properties of the composites were tested using transverse free vibration method.The effects of alkali treatment on the acoustic properties of the composites were studied by acoustic spectrum analysis and comprehensive scoring method.In addition,the mechanical properties and acoustic properties of the composites were compared with wood eucalyptus often used in the national percussion instrument.The results showed that alkali treatment lowered the mechanical properties of the four kinds of natural cellulose fabrics.The fabric counts and yarn crimps in warp and weft directions were all increased.However,the mechanical properties of the ramie and jute reinforced composites after alkali modification were improved.Compared with the untreated composites,the warp tensile strength and modulus of the alkali treated ramie composites increased by 23% and 17%,the warp flexural strength and modulus were increased by 11% and 10%,while in the weft,there is no difference.After the alkali treatment,the warp flexural strength and modulus of the jute composites were increased by 6% and 29%,respectively.while their weft flexural strength and modulus were increased by 15% and 26%,respectively.However,their tensile properties were not significantly changed.The tensile properties and flexural properties of the hemp and flax composites after the alkali treatment were somewhat decreased.By observing the surface morphology of the fibers and the tensile fracture failure morphology of the composites before and after alkali modification,it was found that the impurities attached to the fiber surface of ramie and jute were removed by the treatment,while the surfaces of hemp and flax fibers show not much impurities before and after the alkali treatment and their surfaces became smoother.Post mortem analysis for the composite showed that the alkali treatment improved the interface in the ramie and jute composites but weakened the interface in hemp and flax composites.The mechanical properties of the composites were determined by the crimp of the yarns which influence the orientation of the fibers as well as the fiber/matrix interfacial properties.The outcome of the composite property change was resulted from the balance of the two factors.Through acoustic spectrum analysis,it was found that after the alkali treatment,the natural frequencies of the hemp and flax composites decreased,while those of the ramie and jute composites increased.The comprehensive evaluation of the acoustic vibration performance of the composites was carried out by comprehensive scoring method.The results showed that the alkali treatment raised the acoustic comprehensive scores of the ramie and jute composites while those of the hemp and flax composites were lowered.The changes of the acoustic properties of the composites after the alkali treatment were likely resulted from the changes of the interfaces between the fibers and the epoxy resin as shown in the post mortem analysis.Comparing the mechanical properties and acoustic properties of natural cellulose fabric/epoxy composites and eucalyptus,the results showed that,except for the flexural strength of hemp composites,which is superior to eucalyptus.The mechanical and acoustic properties of the composites are in between the horizontal and vertical stripes of eucalyptus,and the composites have similar acoustic spectra to eucalyptus.Due to the similarity in the warp and weft structures of the fabrics adopted in the study,the composites showed similar properties in the two directions or almost planar square-symmetric properties.It is therefore possible to alter the fiber volume fraction,fabric weave,yarn crimps and fabric counts in warp and weft directions in the composite to simulate the mechanical and acoustic properties of eucalyptus.