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This study presents an experimental study of the quasi-static axial compression and compression–compression fatigue behavior of a three-dimensional braided carbon/epoxy composite tube. Three kinds of tubes with different braiding angles, i.e. 25º, 35º, and 45º were used to examine the dependence of fatigue behavior on the braiding parameters. Quasi-static compression and compression–compression cyclic loadings were carried out on the braided composite samples. The S–N [stress and number of cycles to failure] curves, strain–N (number) curves, and damage observation were used to evaluate the behavior of the braided tubes under fatigue loading. The test results showed that braiding angle had significant effect on the ultimate compression strength (UCS) and the number of cycles per stress level that the sample could withstand. The tube with 25º braiding angle had the highest UCS while the tube with 45º braiding angle accumulates high number of cycles for the same stress level as compared to other samples. Damage occurred along the braid angle for 25º tubes while matrix crack plus bulging occurred in the tubes with 35º and 45º braiding angles. [ABSTRACT FROM AUTHOR]

Studies of numerical simulation and experimental validation are carried out on the planar orthogonal braided composites cantilever beam. On the basis of single-cell model, the model of 1 × 1 orthogonal braided fibre structure is established with the SolidWorks engineering drawing software. Six different loading models are analysed using the finite element software ANSYS. The effective elastic constants are obtained with the homogenisation theory. The finite element model of a cantilever beam is then established, which is made of orthogonal braided composites, where the angle between fibre orientation and periphery varies from 0° to 90°. The experiment is carried out and the natural frequencies are obtained using the free vibration measuring method. The effects caused by the additional mass of sensor are eliminated according to vibration theory, and the results are consistent with those obtained by numerical simulation. [ABSTRACT FROM AUTHOR]

Three dimensional braided composite materials exhibit better performance in terms of structural integrity, through-thickness strength and impact resistance, than laminated composites. Other advantages regarding production are the ability to produce composite structures with intricate geometries close to the near-net-shape, and also with continuous changes in its cross-section. These properties are a consequence of the internal geometry of the 3D braided composites, in which yarns are interlaced following specific patterns programmed on a braiding machine. In this article, the operation of a typical rotary braiding machine is emulated in order to automatically obtain the geometry of a braiding unit cell. Once the geometrical description is obtained, a finite element model has been developed in order to carry out virtual testing of 3D composite materials. An AS4/epoxy braided material system has been virtually tested and a theory-experimental correlation has been performed for the longitudinal modulus and yield strength compression, using a failure criterion based on constituents and interface failures. [ABSTRACT FROM AUTHOR]

Fibers are the basic structure in yarns, and yarns are the basic structure for fabrics. Although the approach described can be applied easily and naturally to fibers, especially when dealing with composite-material fabrics, the applications presented are thought of primarily as yarn-based assemblies. Hence, when talking about the developed model, 'yarn' and 'fiber' can be thought of as interchangeable. In general, fabric models assume underlying yarns to be of zero thickness. Those who have looked at yarns as three-dimensional structures have limited themselves to simple geometric arrangements of the yarns or have used assumptions which are non-geometric in order to simplify the model. A basic model is proposed which treats a yarn as a true three-dimensional solid object. This approach is first applied to three yarns twisted together to form a rope-like bundle. Next, the technique is used to model a woven fabric; the Peirce geometry is analyzed, and then the model is extended to look at fabric shear. An approach for a three-yam braid is presented as the most recent work. [ABSTRACT FROM AUTHOR]

This paper demonstrates a unified approach to the design, analysis, and manufacturing of three-dimensional braids for structural composites. The linkage between manufacturing and performance is accomplished through a processing-science model. By combining a topological model of the braiding process with geometrical and mechanical models, a process structure/properties relationship for 3-D braid-reinforced composites is created to form a communication link between structural-design engineers and textile-materials engineers. [ABSTRACT FROM AUTHOR]

Developments in fibres* matrices, and composites manufacturing are reviewed, with particular attention to textile methods. Although the textile manufacturing processes are more complex than injection moulding and laminating, they have advantages in greater control of fibre placement and in ease of handling preforms. 3-D shell structures can he made by various methods, including knitting, weaving, and braiding, but the most important development is in 3-D integrated structures. The methods include false interlacing by winding, stitching, and the true textile interlacing of 3-D weaving and braiding. The research challenge involves problems of topology and geometry, structural mechanics, engineering machinery, and software. [ABSTRACT FROM AUTHOR]