3D warp interlock fabrics

Cuong H, Boussu F, Kanit T, Crdpin D, Imad A. Effect of frictions on the ballistic performance of a 3D warp interlock fabric numerical analysis. Appl Compos Mater 2012 19(3-4) 333 7. 

Taking into account all these research results done on the forming process, the forming bench used in our laboratory (Najjar et ah, 2013) to obtain the final preform from a 3D warp interlock fabric in the automotive production requirements has been adapted to a fast, safe and ambient temperature stamping process, as shown in Figure 10.1. 

The hemispherical punch has been first used to analyse the forming behaviour of the 3D warp interlock fabric both in the warp and weft directions and then check the estimated anisotropy. The box shape has been used to analyse more precisely the forming behaviour on a shape with the same concerns as in the final parts. 

Using the same 3D warp interlock fabric for the two different shapes of punch, local and global deformations of the two preformed samples can be checked following the different path of yams inside the stmcture and checking the resulted locations of initially equidistant red points marked in the fabric surface (Figure 10.4). 

To sum up, the realistic as-woven geometry of the 3D warp interlock fabrics should be well represented in numerical model, and the variation of the cross-sectional shape of the yams should be taken into account. The identification of a material s mechanical behaviour law is often difficult to achieve for a 3D warp interlock structure. It should highlight here that the computational cost of the forming simulation of the thick warp interlock preform is more important as compared to the 2D fabric therefore, it should find a good balance between forming simulation accuracy and computational efficiency. 

D warp interlock fabrics, constituted by commingled yams, can be preformed at room temperature and this cool forming tends to be better controlled and seems to be more economical (Vanclooster et al., 2009a,b Padvaki et al., 2010 Thomanny and Ermanni, 2004 Zhu et al., 2011). The increase of temperature and the resin consolidation phases after the forming can be achieved under isothermal conditions thanks to a closed mould. By this way, it appears easier to avoid defects during the non-isothermal thermoforming process, especially for thick preform. 

All the thickness variation values measured at the seven selected points (see Figure 10.8) of the three types of 3D warp interlock fabrics are summarized in Table 10.2. 

Figure 10.9 Thickness variation after forming of the three different 3D warp interlock fabric architectures.

Figure 10.11 Material draw-in measured values in warp and weft directions of the three different types of 3D warp interlock fabrics.

Due to the higher thickness value of 3D warp interlock, the exact positions of warp and weft yams, respectively, located oti the top and bottom of the 3D fabric, have to be checked during the forming process. To measure the slippage between the external layers, coloured yams have been woven on the two external surfaces of the 3D warp interlock fabric to create symmetrical and regular grids (Figure 10.12). Fifty locations have been chosen and marked vis-a-vis oti upper and bottom surfaces. 

The crossing of these yams creates different points at which spatial positions are compared once the forming step is done. Then the interlayer sliding is determined by the distance between the orthogonal projections of the two external points on the middle plan (Bel et al., 2012). For instance, the measurement of the interlayer sliding value for the point number 3 located in the two external 3D warp interlock fabric layers is represented in Figure 10.13. 

Figure 10.12 Grid construction of coloured yams inserted on top and bottom surfaces of the 3D warp interlock fabric.

A first comparison of the three different types of 3D warp interlock fabrics using the four measured parameters can be done and helps to highlight the influence of the weave diagram on the global behaviour of the final preform in both warp and weft directiOTis after the forming process using a semi-hemispherical punch. 

A second comparison of the three types of 3D warp interlock fabric helps to reveal a more local behaviour at each point of the final preform due to their different weave diagrams. 

However, using new commingled yams and new gusset shape leads to a higher and non-equilibrated consumption of 3D warp interlock fabrics during the forming process. 

However, a better knowledge of the forming behaviour of 3D warp interlock fabrics has been obtained and will soon be used for a simulation step. 

Thus, the research work of Trifigny (2013) has consisted of observing the kinematics of the weaving process by checking aU the contacts and dynamic loads applied on yams. Based on these observations, the design of electrically sensitive and mechanically resistant sensor yams has been achieved, tested and calibrated. Then, dynamic measurements on the different loom locations have been conducted to detect the local distribution of elongation on different warp yams, especially applied on two different tow counts of continuous E-glass yams inserted into 3D warp interlock fabrics. 

Videos have been made using a high-speed camera, Photron APX, with a maximum resolution of 1024 x 1024 pixels at 2000 pictures/s (Fig. 17.3), positioned at different locations of the industrial weaving loom with a speed production of 100 picks/min and a fabric width of 140 cm for the production of the 3D warp interlock fabrics with E-glass yams. 

Two different 3D warp interlock fabric architectures have been produced using, respectively, each of the two yam s count separately with the product parameters described in Table 17.3. Sensor yams have been used as binding warp yarns inside the two 3D warp interlock architectures. 

We would also like to warmly acknowledge Professor Stepan Lxrmov and his team for providing us the Wisetex software (Lomov et al., 2000), helping us to represent 3D warp interlock fabrics geometry in all the 3D views. 

Boussu, F., Cristian, 1., Nauman, S., July 22, 2015a. General definition of 3D warp interlock fabric architecture. Composites Part B 81, 171 — 188. 

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