Study on the Permeability of Woven Reinforcement with Fractal Theory
|Keywords||woven performs permeability pore structure fractal geometry RTM fractal model|
In the process of manufacturing composites, permeability is the important Parameter for describing the resin flow, it can be used to token the hardness of resin flowing fiber aggregation. Permeability is also the important Parameter for computer simulation; it helps to design the fibrous reinforcements. The permeability decides the composite’s quality and efficiency. So, it can drive the quality and efficiency of composites if we can study the permeability of fibrous reinforcements and control the factor.As the main processing of composites, the woven processing has many advantages, such as quick development of equipment, faster production, and higher efficiency of cost. Multi-axial fabric, multiply fabric and three-dimensional fabric can be get by reforming for traditional two-dimensional weaving machine, furthermore, woven composites have batter dimensional stability, At present, fabric-reinforce materials had been developed into 2.5D and three-dimensional fabric from single fabric.In the study of permeability for woven-reinforce materials were scaled by experiment measure and ideal model. The experiment measure method was tangle some and affected by objective factor. At the same time, permeability had obvious difference between ideal model and actual. Consequently, looking for a math model for permeability transportation property which was resolved by theory is a problem, which was the most attractive and the most challenging in "perforated medium permeability transportation property" field.The formula of fractal dimension was deduced according to the amended model of plain weave, twills, 2.5 D woven performs then the pore area dimension and curved dimension were calculated based on the structural Parameters of them.Firstly, woven preform pore structural theory model revisionThe woven reinforced material in weaves compound with takes shape in the process, as a result of the external force function, it has the very big change, the former simplification model has not been able to attribute its real structure, this article uses the theoretical model as well as the picture gathering method has analyzed the woven reinforced material structure characteristic. Through the experimental observation and to weaves the reinforced material weaving with to take shape the process analysis, to weaves the reinforced material the hole structural model to carry on the revision, establishes to take shape the structural model with the compound material which in the process tallies. In the middle of the revision model, did not have in the former model regular pore, moreover obtains in the reinforced material the resin mobile channel is continuously changes. After the revision model fiber on the weave reinforced material section is the random distribution.Secondly, woven reinforced material fractal characteristic confirmationIn after the revision model has not been allowed simply to calculate the hole, its interior is chaotic, therefore already could not canyon accurate indicating with the traditional analysis method to it, then we have introduced one emerging science and the research technique - fractal geometry. First elaborated the fractal theory basic principle, and has inferred the object fractal characteristic judgement basis, then the use counts the box law principle, to weaves the reinforced material the section picture to carry on processing, and confirms the weave reinforced material using the VC++6.0 programming language compilation procedure the hole structure to conform to the fractal characteristic, proved the weave reinforced material the hole structure may apply the fractal theory to conduct the research.Using the fractal geometry fundamental research textile fiber reinforced material structure, has provided one kind of quite good research mentality and the method for the research reinforced material penetrating quality, microscopically causes the quota description textile fiber reinforced material, the macroscopic complexity to become possibly, for the precise portray reinforced material mechanical physical property, promulgated and simulates the textile fiber reinforced material the sufficient mold rule to provide the reliable Parameter and the theory support.Thirdly, Weave reinforced material fractal dimension solutionThe fractal dimension has measured the fractal object packing space ability; it discussed from the measure with the symmetrical theory aspect has portrayed the fractal. Because in the weave reinforced material cellular construction the different position hole structure has differently, section surface integral shape dimension because of position difference and difference, object randomness, was the description fractal object most basic characteristic Parameter. Therefore, this article separately extracts the different position the fractal dimension, causes to weave the reinforced material fractal characteristic the attribute to be more accurate. This article according to revises after the even grain, twills, the2.5D weave reinforced material model infers three kind of weaves reinforced materials the fractal dimension solution, and then extracts its area dimension and the curving dimension through the design Parameter.Fourthly, Weave reinforced material permeability fractal model establishment.Then use this model separately to calculate the even grain, twills as well as the 2.5D woven reinforced material permeability theory value on the two representative sections. The compound material permeability calculates which this model forecast was a range.Fifthly, Theoretical model experimental confirmationThe permeability survey mainly uses the RTM principle, its main principle for uses injects the equipment to pour into the special-purpose injection resin system the closed cavity, in the cavity has set takes shape in advance according to the performance and the structure request design weave reinforced material the body, the mold peripheral seal and the fastening, according to Darcy’s law, recording pressure, resin viscosity, as well as resin mobile front, thus determines the weave reinforced material the permeability observed value. And carries on basically the contrast, the measurement result is in the range of the fractal model computation result, finally has analyzed between the computed result and the experimental observed value the difference reason.In summary, this article according to the capillary vessel fractal model, unifies the Darcy law, establishes the permeability fractal model, may forecast the permeability well, moreover the Kozeny-Carman equation which knew very well with the people compares, eliminated the empirical constant. Therefore, the application is divided the shape theory and the method studies weave reinforced material the permeability to have the obvious superiority compared to the Kozeny-Carman equation.