| Plant fiber textile structural composite is the excellent product as developing and interacting with each other between textile science and composite disciplines. It will be better to understand the mechanical properties of material by establishing complete evaluation system from uniaxial, biaxial, bursting to 3-D,because of the orthotropic property. Meanwhile, exploration in preparing plant fiber woven structure composite will further help to expand using of plant fiber in engineering application. Firstly this paper verified accuracy of 3-D composite materials evaluation system by comparing with the Instron mechanical testing machine 5800. Strain-field of ramie woven under biaxial loading was characterized by using digital speckle correlation method. Interactive effect between warp and weft were found, exchange mechanism with different value of loading thresholds and different angles were investigated.By comparison and analysis mechanical properties of woven fabrics from multi-angles, namely uniaxial, biaxial, bursting,3-dimensional loadings, providing a new idea for multi-dimensional evaluation and experimental method. Then, the water-based epoxy resin, phenolic resin and isocyanate textile structural composites were prepared. Their mechanical properties under uniaxial, biaxial and three-point bending along with anti-light discoloration were also compared, obtaining a optimum matrix for textile structural composites. Multi-factor single-level evaluation model of the preparation technology, which is according mechanical properties of natural fiber fabric composite, is established by using theory of fuzzy comprehensive evaluation. At last, mechanical behavior of natural ramie/isocyanate laminate composite with holes was investigated by biaxial tensile method. Radial and circumferential strain near different size of holes were presented, and mechanical properties with different loading ways were also characterized. The study's main results are summarized as follows:1. Accuracy of the system and measuring of strain-filedAccuracy of 3-D Composite Material Analysis System the system can meet the experiental need. It is available for DSCM to measure the plant fiber fabric' displacement-filed and strain-filed under biaxial tension.2. Experimental method of biaxial tension Pre-tension (≤10N), tensile rate (<0.125mm/s); cross-shaped specimen with gentle arc connecting transition are more appropriate as ramie fabric biaxial tensile test parameters; This factors can better meet the experimental conditions that the maxim stain happened at the center, and strain spread uniformly.3. Interactive effect between warp and weft of ramie wovenInteractive effect between warp and weft existed and the influence of load at weft to warp were larger than warp to weft; as the load at warp direction linear increased, force values at warp direction nonlinear increased and load ratio, the absolute value of strain at warp and weft direction decreased.4. Mechanical properties of woven fiber woven under multidimensional loadingsThe results indicated that biaxial tension had lower breaking strength in the warp direction and larger in weft as compared to uniaxial tension but with larger CVs in both directions under biaxial tension. Under 3-D loadings, there was a significant linear relationship between breaking strengths of warp and weft. The degree of linear correlation determined by synergism of bursting strength was over 12.53%.5. Properties of composites with different resins and preparation technologyBoth water-based epoxy resin plate and isocyanate resin plate showed orthotropy and elastoplasticity, while the performance of phenolic resin board is linearity and simultaneous brittle-fracture on both X and Y direction; load changes in fracture direction have a negative impact on other direction at the moment of breaking and impact degree has a positive correlation with the loading values in fracture direction. Anti-light color properties for phenolic resin plate is better than others, and light stability on apparent color for isocyanate plate has been enhanced by boiling and alkali treatment.Multi-factor single-level evaluation model of the preparation technology, which is according mechanical properties of natural fiber fabric composite, is established by using theory of fuzzy comprehensive evaluation; three elements of hot-pressing and paving way are evaluated by using comprehensive fuzzy model, obtaining sorts of the best preparation technology. The results show that:the best technique follows:hot-pressure, hot-pressing temperature, pressing time and paving way are respectively 3MPa,120°,5min, [(0/90)]7.6. Mechanical properties of natural fiber textiles laminate with holeDistribution of displacement field around the hole is uniform with load changes in linea, while the load was closing to failure, non-linear distribution and high strain points appeared,. As the radius of the pore increased, average strains in X,Y direction reduced within the same area around the hole under biaxial loads and fluctuation of strain decreased slightly. Strength under biaxial load is lower than the one under uniaxial tensile and the reduction ratio, which increased with the size of pore radius raised is about 14%～27% of the uniaxial load.The results show that:using multi-dimensional method to evaluate mechanical properties is a novel and fine approach which can be more objective and comprehensive to response the properties of anisotropic materials. Both fuzzy comprehensive evaluation for composite'preparation and the using of digital speckle correlation method to characterize strain-filed are exactly accurate and effective methods. Plant fiber textile structural composite have unparalleled research and application'value, with its mechanical properties meeting the requirements of composite materials used in general engineering. |
PDF Full Text Request