Braid angle is a key factor associated with the mechanical properties of braided composites, so accurate prediction of this angle is of vital importance for the design and manufacture of braided preforms. This paper presents a theoretical model for the prediction of braid angle at any point of a mandrel with constant arbitrary cross-section by taking into account the kinematic parameters of circular braiding machine. The proposed theoretical model pays particular attention to two parameters that strongly affect the braid angle, namely the position of fell point on the mandrel’s surface and the yarn length between this point and the carrier. Both of these parameters undergo continuous change during braiding and thus should be calculated on a point-to-point basis. The model was validated by a series of braiding experiments conducted, using a circular braiding machine, on mandrels with circular, elliptical, and oval cross-sections and then determining the resulting braid angles over the mandrel’s surface by an image processing method. The experimental results showed the high accuracy of the proposed theoretical model in predicting the braid angle for mandrels with constant arbitrary cross-section. Thus, the proposed model can contribute to faster and more accurate design and manufacture of braided composite preforms.

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Bed sheet fabric as a kind of home textile has been used since many years ago. Bed sheet is very significant because of being in direct contact with body consecutively for a long period of time. Bed sheet surplus qualitative parameters such as fiber substance, method of printing, finishing, etc., have a significant parameter called handle. In this paper, we proceeded to consider the relationship between fabric handle as a qualitative parameter and physical parameters which influenced the fabric handle using statistical modeling. The statistical model used was ordinal regression model. The modeling was done by SPSS V.19 software. We used 15 bed sheet fabrics. For subjective evaluation of 15 bed sheet fabrics, we selected 55 persons randomly as sample members according to Cochran's formula. Population was selected from senior BS students and MS students at Isfahan University of Technology (IUT). We asked persons to classify bed sheet fabrics based on their preference of fabric handle from 1 (lowest) to 5 (highest). Physical parameters values were obtained through standard experiments. Finally, we analyzed obtained data through SPSS V.19 using ordinal regression model. Results showed a satisfying match between extracted data from the software and the real data from person's evaluation.

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Reinforcement of the thin-wall structures under internal pressure by braiding method has many applications in different industries. In this way, the effective braid angle determination will be important in achieving a stable and resistant structure. The main aim of this work was finite element modeling and experimental validation of these structures under internal pressure. Therefore, a thin silicon pipe as the core was covered with different braid angles in braiding machine and then was subjected to internal pressure. After that, a finite element model was implemented for a repeatable part of the samples as a unit cell using ANSYS software to calculate the pressure-diameter diagram of the samples. Finally, in order to verify the accuracy of the finite element models was recorded the increase in braided pipes diameter up to rupture by camera and prepared pressure-diameter diagram for all samples by image processing method. The comparison of the finite element method results and image processing showed a good agreement with high accuracy. Also was observed in finite element modeling that the relationship between diameter-pressure in 55 degrees was rather linear, generating forces in the pipe surface of thin silicon due to internal pressure along braid strands direction as confirmed by image analysis.