Automatic Measurement Of Surface Parameters Of 3D Braided Fabric Based On Image Processing

Three dimensional braided composite is a new type of composite material, which is made up of preform. It is widely used in medical, automotive, aviation, aerospace, military and other fields. The braided angle and pitch length have an important influence on the mechanical properties of the composite material. In order to meet the requirement of the mechanical properties of the composites, the braided angle and pitch length must be measured and controlled. In textile industry, the surface parameters of 3D braided composite material still relies on manual operations with the help of magnifier and micrometer, which wastes much time and manpower. And large measurement error is easily caused. The technique of automatic measurement of the surface parameters of 3D braided composite based on image processing technique is essential to improve the level of automatic measurement of textile industry.In this thesis, the measuring method of surface parameters of 3D braided composite material is studied. A method for measuring the surface braided angle of 3D braided composites preform based on Hough transform is proposed. Firstly, the deviated image is corrected. The flower pitch of each row is segmented according to the position of the peaks and troughs of the horizontal gray projection curve, and the direction of texture of the preform is calculated. The first incomplete flower pitch of each row is deleted based on Hough transform so that all the flower pitches are segmented. Then, the straight line of each flower pitch is detected based on Hough transform, and the braided angle is calculated according to the slopes of the two cross straight lines. According to the periodicity of surface texture of 3D braided composites, a method for measuring the pitch length based on gray projection is proposed. Firstly, the number of flower pitch of each row is calculated, and the length of the first flower pitch of each row is calculated based on Hough transform so that the projective area can be segmented. Finally, all the pitch length can be calculated based on the horizontal gray projection.Experimental results show that the method can overcome the influence of noise. The flower pitch and the projective area can still be segmented from the incomplete edge of image. The proposed method can effectively measure the surface braided angle and pitch length of the preform.