Braiding Simulation and Prediction of Mechanical Properties

Abstract

Rotary braiding is a cost effective method to manufacture near net shaped preforms that generally have a closed section and may have an arbitrary shape if braiding is performed over a shaped mandrel. The reinforcement architecture can be varied by the number and spacing of active bobbins, and by the speeds used to 'take-up' the braid and move the circumferential bobbins. Analytical methods are available that can reliably predict yarn paths and the final braid meso-structure for simple regular sections, and further analytical methods have been proposed to estimate composite braid elastic mechanical properties. A full simulation chain using the explicit Finite Element (FE) technique is presented for composite braid manufacture and mechanical stiffness prediction of the final composite. First simulation of the braiding process provides detailed information on yarns paths and braid meso-structure, from which Representative Volume Elements (RVE) of the braid may be constructed for analysis of stiffness properties. The techniques are general and can be applied to any braid geometry. A specific problem of meshing the yarn structure and interspersed resin volumes is overcome using conventional solid elements for the yarns and Smooth Particle Hydrodynamics for the resin, with link element to join the two constituents. Details of the background theory, braid simulation methods, meso-model analysis and validation again analytical and test measurements are presented.

Numerical modelling of 3D woven preform deformations

“…A novel technique was developed by Pickett et al [19] whereby an initial reference geometry with solid, non-interpenetrating, circular cross-section beams was generated alongside a 'pre-stressed' reference geometry with more realistic elliptical cross-sections attributed to the yarns. The 'initial metric method' in FE code PAM-CRASH was then used to deform the initial mesh towards the reference mesh whilst being bounded by moulding plates and preventing any yarn interpenetration.…”

Computational Prediction of the Mechanical Properties of a 2D Triaxially Braided Composite

“…With the aim of covering the influence of braiding and forming on the stiffness and strength, a meso-scale FEM model was created and analyzed using ESI's Pamcrash Explicit solver. The model utilizes the output of braiding process simulation [1], performed with a 1D representation of the yarns. These yarn trajectories are transformed into a shell of yarns with width and thickness corresponding to the fiber diameter (7 μm) and its content in the yarn (24 K).…”

Experimental and numerical studies on the braiding of carbon fibres over structured end-fittings for the design and manufacture of high performance hybrid shafts

“…The studies however used single chains of beam or bar elements to represent each yarn, and were limited to smooth (i.e. non-structured) mandrels [20][21][22]. It should be noted that some complex phenomena observed in reality, such as yarn cross-sectional deformation and yarn splitting around surface protrusions, could not be fully captured.…”

“…It should be noted that some complex phenomena observed in reality, such as yarn cross-sectional deformation and yarn splitting around surface protrusions, could not be fully captured. In addition, these analyses [20][21][22] appear to have been tailored to the manufacture of specific components, and as such would lack the versatility and scalability required for a more general use. For example, yarns had to be modelled in their entire lengths from the very beginning of the analysis, with several thousands of beam elements stretching out radially away from the guide ring, as if attached to an immense braiding wheel.…”

“…In this way, all factors influencing braid quality, such as friction between yarns, sliding contact against the guide ring, and frictional contact against the mandrel are considered as individual variables [20][21][22]. The studies however used single chains of beam or bar elements to represent each yarn, and were limited to smooth (i.e.…”