Papers by Keyword: Stitch

Abstract: In this paper static analysis of a cantilever functionally graded sandwich beam under uniform distributed loads is carried out numerically. The beam is composed of two glass fiber reinforced plastic (GFRP) facesheets and a graded Corecell A-series foam core. The composite skins and foam core are stitched together using the same glass fiber. A finite element (FE) model is developed employing a FE commercial code to determine the stresses and deflections. To find the effect of quality of foam gradation through the thickness of the core on the deflections and stresses numerical experiments are performed. Results revealed that the quality of gradation of the foam core affected the displacements and stresses significantly so that an optimal gradation of foam can minimize the deflection, stresses and weight of the sandwich beam.

Abstract: Non-Crimp Carbon Fabric (NCF) consists of unidirectional plies which are kept together by stitching yarns arranged in a number of different orientations relative to the fabric production direction. It is reported that NCF possesses excellent drape performance compared to woven fabrics. However there is not a clear criterion of a drape evaluation on the drape characteristic of the NCF. In addition, it is not clarify that stitch pattern and stitch tension influence on the drape characteristic of the NCF. Moreover, in existing bias extension test, measurement of shear angle is based on the pin-jointed net (PJN) approximation. The PJN approximation doesnt takes into consideration the fiber sliding and the effect of the stitched parameters of the NCF. In this study, the bias extension test based on the measurement of shear angle by non-contact 3D deformation measurement system was conducted to evaluate the drape performance of the NCF. We made a proposal of the formability evaluation index based on the measurement results. Moreover, the 3D draping tests were conducted onto hemisphere geometry and regular tetrahedron, in order to verify availability of the formability evaluation index. The availability of the formability evaluation index was verified.

Abstract: The stitched composite T-joints and Z-pinned ones subject to bending load were investigated in this paper. A simple theoretical model characterizing the failure process of through the thickness reinforcement (TTR) during mode I delamination was presented. The experimental results showed that the initial damage load and maximum load of stitched specimens are higher than that of Z-pinned ones, while the energy absorption of stitched specimens during delamination is lower than that of Z-pinned ones. The energy absorption values predicted by the present model meet the experiments reasonably well. High friction force at the interface between TTR tow and matrix, with a long pull-out displacement of the tow, helps to improve the delamination resistance.

Abstract: The non-crimp fabric (NCF) have an advantageous combination of high material properties and low cost for processing, and overcomes the disadvantages of the crimp factor of woven fabrics, providing full use of modulus and strength of reinforcing fibre. For using NCF, different stitching tension and thread of non-crimp fabrics may cause the mechanical properties of CFRTP. In this study, it is aimed to clarify the effect of stitching tension and thread of non-crimp fabrics on tensile strength of CFRTP. The disorder degree of the thickness direction in the fibre bundle and the ratio of resin rich area were examined by the SEM image analysis. There is the inverse correlation between tensile strength and the disorder degree to the thickness direction in the fibre bundle.

Abstract: A novel algorithm and experiment using phase retrieval to test aspheric mirror without auxiliary optical elements has been developed. To test aspheric mirror without auxiliary optical elements, a new algorithm has been invented to overcome the calculation difficulty due to the significant departure of aspheric surface from a sphere. In this algorithm, the aspheric surface is fitted into several annular ellipse sub-apertures, and each sub-aperture aberration can be retrieved the same as ball mirror testing. The whole aspheric surface can be retrieved by stitching all the subapertures together. An experiment has been carried out to test the validity of this algorithm.