Production And Structural Analysis Of Variable Thckness 3-D Woven Fabrics

As a perform of textile structural reinforced composites, the warp and weft of 3-D woven fabric possess an inplane distribution as well as a distribution along thickness-direction, forming an interspace reticulate structure which overcomes the fatal disadvantage of low interlaminar strength of laminates and significantly improves the interlaminar properties and damage tolerance while maintaining the advantages of high specific rigidity, high specific strength, corrosion resisting and anti-fatigue, etc. In addition, its overall formability and designability endow the 3-D woven fabric with incomparable advantages, which is irreplaceably utilized in protection works fields such as aviation, spaceflight, shipping, construction, and so forth.With the deep exploration into the various properties of 3-D woven fabric reinforced composites, the research focus turns to the structure design and formation of various of 3-D woven fabric with Shaped cross-section. Variable thickness 3-D woven fabric is also of Shaped cross-section, which is applied practically in a wide range such as propellers of planes,blade of sails and so on. Traditionally, the blade is manufactured in a moulding way, whose low interlaminar properties limit its utilization. Furthermore, since blade would bare an enormous stress effect when it functions, it is significant to construct a comparably precise mechanical model to predict the materials' mechanical properties. The construction of mechanical model should be based on an objective and reasonable representation of the fabric's geometric construction, yet the existing geometric construction is too general and ideal. Therefore, the present thesis firstly designs and produces several kinds of basic-structured 3-D woven fabric, represents the geometric structure based on the real fabric structure, chooses the reasonable basic structure subsequently and further designs a 3-D woven fabric with even thickness of continuous change.Based on multi-layer stitched (including stitched itself and stitched by weft), angle-interlock tissue and orthogonal tissue, the thesis successfully realizes the accomplishment of designing and producing the 3-D woven fabric and achieves the three-dimensional constant thickness woven fabric with stable structure and uniform appearance through a whole process of structure-design, weaving-machine transformation, technique design and weaving. Fixed the structure of the achieved 3-D woven fabric by collodion, sliced it along the warp and weft directions respectively and observed the distribution of the yarns'longitudinal form and section pattern of real structure through a combination of slice graphics and image processing techniques, the thesis found the structure of warp yarns of multilayer stitched was characterized as that stitched itself prohibited sinusoidal distribution longitudinally and raceway-shaped transversally and the stiched by weft prohibited sinusoidal distribution longitudinally and convex lens-shaped transversally; and the structure of weft yarns of multi-layer stitched was characterized as that its stitched itself prohibited linear distribution longitudinally and crescent-shaped transversally and the stitched by weft prohibited linear distribution longitudinally and convex lens-shaped transversally. The structure of warp yarns of angle-interlock tissue was characterized as that angle-interlock tissue prohibited a form of curves and straight lines combined longitudinally and convex lens-shaped transversally; and the structure of weft yarns of angle-interlock tissue was characterized as linear distributed and the cross-section was parallelogram-shaped and fan-shaped. The structure of warp yarns of orthogonal tissue was characterized as straight-linear distributed and the cross-section was rectangle-shaped. The hanging yarn structure of orthogonal tissue was shaped like a combination of curves and straight lines with a raceway-shaped cross-section. The structure of weft yarns of orthogonal tissue was characterized as straight-linear distributed and the cross-section was rectangle-shaped and arch-shaped. These findings will provide a significantly reliable basis for the structure design of the fabric with variable thickness and the construction of successive geometric model and even the mechanic model.In the light of the findings mentioned above, during the design and production of variable thickness 3-D woven fabric, with the adoption of the stitched by weft which holds a higher designablity in the direction of weft as the basic stitch, the design in factors such as tapered structure, weave construction, changes in the structure of the program, thickness, weft density and fabric appearance, and further exploration into the loom mechanism, technological parameter and weaving, a set of completely new and practical weaving techniques and skills of 3-D constant thickness woven fabric was achieved.After the fixing of the structure of variable thickness 3-D woven fabric after下机, the thickness and structure of different sections were examined. The results showed, the structure design of variable thickness 3-D woven fabric is reasonable, the technique parameters are practical and the techniques adopted are effective, which would shed light on the more complex design and production with high performance fiber in the future.