New method on the elastic properties of stitched composites ———Flowf ield modelⅠ: Elastic constants calculation of the stitched laminar

Based on the similarity between the orientation of the fiber in the stitched laminates and the st ream inthe flow around a cylinder , a flow field model is built for the elastic constant s of the stitched laminar , which is asteady 2D non-compressible non-viscous ideal flow without swirl in a finite space. The boundaries of the flow fieldand the unit cell of the stitched laminates are identical , and the surface of the body in the flow field is the same as thesection shape of the stitch thread. The velocity variation in the flow field describes the fiber volume f raction variationin the unit cell of the stitched laminar , and the st reamline shape describes the fiber orientation. Using the flow fieldmodel , the elastic properties of the stitched laminar are calculated by the micromechanics and the homogenizationmethod , and the result s are in good agreement with those of the test . Finally , the effect s of the stitch parameters onthe laminar elastic constant s are discussed.