Fibre architecture

In the following paragraphs an overview of damage due to thermal shock and its effect on the mechanical properties of CMCs with different fibre architectures is provided for a number of different reinforcement architectures. Subsequently, the effect of thermal shock on interfacial properties is discussed, followed by a description of attempts to analyse and model the thermal shock behaviour of these materials. 

Preform fibre architecture for ceramic-matrix composites, Ko, 1989 [139]... 

The losses per junction are between 0.4 and 0.2 dB. In practical fibre architectures optical splitting is also very important, e.g. [177]. 

F. K. Ko, Preform Fibre Architecture for Ceramic-Matrix Composites, Am. Ceram. Soc. Bull. 68, 401-414 (1989). 

Yang and Chou " have shown schematically the change in these moduli, E and E, for a carbon fibre-reinforced epoxy laminate with a range of fibre architectures, but the same fibre volume fraction of 60% (Fig. 1.3). Such a diagram provides a good starting point for the discussion of textile-reinforced composites. The cross-ply composite has... 

Authors who have investigated damage development in three-dimensional composites of all types have commented on the complexity of the damage,which is a reflection of the complexity of the fibre architecture. For example. Fig. 1.12 shows a schematic diagram of a three-dimensional non-crimp orthogonal weave composite... 

Potluri P, Hogg P, Arshad M, Jetavat D, Jamshidi P. Influence of fibre architecture on impact damage tolerance in 3D woven composites. Appl Compos Mater 2012 19(5) 799-812. 

Brookstein DS, Interlocked fibre architecture, braided and woven, 35th Int SAMPE Symp, Apr 1990. 

Braiding procedures to produce braids with various cross sections have already been developed for the Ist-generation hexagonal braider. It was shown that a wide range of cross-section geometries as well as fibre architectures are feasible (Schreiber et ah, 2009). 

Potluri, P., Hogg, P., Arshad, M., Jetavat, D., 2012. Influence of fibre architecture on impact... 

Pull-off forces typically vary between 30 kN and 235 kN (Shaw-Stewart and Sumerak, 2000) and the pultrasion speed varies between 0.02 and 3.0 m/min, depending on the type of machine used, the wall thickness and the complexity of the cross-section and fibre architecture. In general, mechanical properties increase with decreasing pulling speed, basically because the resin stays longer in the die at slower speeds, and achieves a higher degree of polymerisation. Cross-sections made up of thicker laminates must be produced at slower speeds so that the matrix cures properly inside the die. Thermoplastic matrices allow much faster production and speeds of up to 20 m/min have been recorded (Devlin et al., 1991). 

Typical fibre architecture of the laminates of pultruded profiles (courtesy of Strongwell). 

Most FRP bars exhibit relatively low interlaminar shear strength, as there is generally no reinforcement between layers of axial fibres. Therefore, the performance of FRP bars for shear loads relies mainly on the matrix properties. Shear resistance can be improved by braiding or winding fibres in the transverse direction of the bar or by introducing continuous strand mats in the fibre architecture (ACI Committee 440, 2006). 

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