ROUND ROBIN FORMABILITY STUDY

Transcription

1 ROUND ROBIN FORMABILITY STUDY Characterisation of glass/polypropylene fabrics Tzvetelina Stoilova Stepan Lomov Leuven, April 2004

2 2 Abstract Thiereport presents results of measuring geometrical and mechanical properties of three types of glass/polypropilene fabrics (balanced and unbalanced fabrics, plain and twill 2/2 weaves).

3 3 CONTENTS 1 INTRODUCTION SPECIFICATION OF THE FABRICS GEOMETRY OF THE FABRICS MEASUREMENT TECHNIQUE RESULTS COMPRESSION TESTS ON THE FABRICS MEASUREMENT TECHNIQUE RESULTS FABRIC FABRIC FABRIC MECHANICS OF THE YARNS TENSION BENDING EXPERIMENTAL TECHNIQUE RESULTS COMPRESSION EXPERIMENTAL TECHNIQUE RESULTS... 20

4 4 LIST OF FIGURES Figure 1 Fabric Figure 2 Fabic Figure 3 Fabric Figure 4 Measurement of the yarn width... 9 Figure 5 Cross-section of a fabric. Measurements of the dimensions d 1 and d 2, the spacing p and the crimp height h... 9 Figure 6 Cross-sections of Fabric 1: warp (above), weft (below) Figure 7 Cross-sections of Fabric 2: warp (above), weft (below) Figure 8 Cross-sections of Fabric 3: warp (above), weft (below) Figure 9 Force-displacement diagram without a sample (Instron), x0 corresponds to the moment of first contact of the upper and bottom plates (changed from series to series of tests) Figure 10 Compression diagrams, 1 st, 2 nd and 3 rd cycles, fabric 1. Arrow shows the fabric thickness, measured on the cross-sections Figure 11 Fabric 1. Compression diagrams: Comparison of the compression cycles Figure 12 Fabric 1. Compression diagrams: Nesting effect: almost non-existent Figure 13 Fabric 2. Compression diagrams: Comparison of the compression cycles Figure 14 Fabric 2. Compression diagrams: Nesting effect: approximately 0.1 mm at the highest compression Figure 15 Fabric 3. Compression diagrams: Comparison of the compression cycles Figure 16 Fabric 3. Compression diagrams: Nesting effect: approximately 0.05 mm at the highest compression Figure 17 Tensile diagram of yarns from the fabric 1(one strand 2400 tex) Figure 18 Tensile diagram of yarns from fabric 2 (one strand 1870 tex) Figure 19 Tensile diagram of yarns from fabric 3 (1870 tex) Figure 20 Comparison of the average tensile diagrams of the yarns Figure 21 KES-F bending diagrams of the yarns. Settings of the KES-F: SW1=5, SW2=1, X=0.2, Y=0.5. Yarns from (a) fabric 1; (b) fabric 2, x2; (c) fabric Figure 22 Compression diagrams, yarns from fabric 1: Raw data. Scale of the thickness axis is 1:5 (0.1 mm on the axis = 0.5 mm in reality) Figure 23 Compression diagram, yarns from fabric 1. Points measurements, thick line averaged diagram Figure 24 Compression diagrams, yarns from fabric 2: Raw data. Scale of the thickness axis is 1:5 (0.1 mm on the axis = 0.5 mm in reality) Figure 25 Compression diagram, yarns from fabric 2. Points measurements, thick line averaged diagram Figure 26 Compression diagrams, yarns from fabric 2: Raw data. Scale of the thickness axis is 1:5 (0.1 mm on the axis = 0.5 mm in reality) Figure 27 Compression diagram, yarns from fabric 3. Points measurements, thick line averaged diagram... 22

5 Figure 28 Comparison of the compression coefficients of the yarns from the different fabrics. The behaviour is very similar LIST OF TABLES Table 1 Overview of characterisation of the fabrics... 6 Table 2 Parameters of the fabric, specified by the manufacturer... 7 Table 3 Geometrical parameters of the fabrics Table 4 Tensile diagrams of the yarns from fabrics Table 5 Bending rigidity and bending histeresis of the yarns... 19

6 6 1 INTRODUCTION The work reported in this document, is a part of a round-robin deformability study of glass/pp fabrics, initiated at the ESAFORM 2002 conference in Krakow. This report describes measurements of the shear behaviour of woven fabrics produced by Saint Gobain. The fabrics are woven with commingled yarns, which contain glass/pp in relation 60/40, in twill and plain weave. The tests were performed by Tzvetelina Stoilova, a Marie-Curie Fellow at the MTM department of the KUleuven (from the Technical University of Sofia in Bulgaria) under supervision of Prof. Stepan Lomov. Specifications of the fabrics were sent from Saint-Gobain Vetrotex (USA) by Ms Marcie Williford. Characterisation of the yarns was done in Centexbel Laboratory in Gent, thereby using the KES-F and INSTRON model 6025 with the help of Mr Van de Welde and Dr Jan Laperre. Table 1 Overview of characterisation of the fabrics Fabrics Yarns Specifications Geometrical measurements Mechanical tests Areal density Surface Internal (on crosssections) 1/2/4-layers Picks/ends [yarn/cm] Spacing Compression Areal density Crimp height Thickness Linear density Glass fibre diameter Linear density Width Width Thickness - Bending - Tension - Compression

7 7 2 SPECIFICATION OF THE FABRICS Table 2 Parameters of the fabric, specified by the manufacturer Fabric 1 Fabric 2 Fabric 3 Manufacturer s style TPECU53XXX TPEET44XXX TPEET22XXX* yarns Glass/PP Glass/PP Glass/PP Glass fibre diameter, µm 21 18, Weave Twill 2/2 Twill 2/2 Plain Areal density, g/sq. m Yarns linear density, tex 2x warp 2x1870 weft 1870 Figure 1 Fabric 1

8 8 Figure 2 Fabic 2 Figure 3 Fabric 3

9 9 3 GEOMETRY OF THE FABRICS 3.1 Measurement technique Areal density of the fabrics was measured by weighting the samples ~0.5x0.5 m, linear density of the yarns by weighting the length of ~1.5 m. Surface measurements used scanned (1200 dpi) images of the fabrics: - Picks/ends count was measured at the base of 20 yarns. - Width of the yarns was measured as the distance between points P1 and P2 (Figure 4), averaged for 20 measurements. Figure 4 Measurement of the yarn width Measurements on the cross-sections of the fabrics, both in warp and weft direction, were used to measure: - dimensions of the yarns - spacing - crimp height. Cross-sections were prepared on samples of the fabrics, impregnated with epoxy resin without any pressure. Measurements were done on scanned (1200 dpi) images of the cross-sections (Figure 5). Figure 5 Cross-section of a fabric. Measurements of the dimensions d 1 and d 2, the spacing p and the crimp height h

10 Results Table 3 Geometrical parameters of the fabrics Fabric 1 Fabric 2 Fabric 3 Warp Linear density, tex (one strand) d1, mm 1.20 ± ± ± 0.27 d2, mm, in cross-sections 2.29 ± ± ± 0.59 on the surface 2.72± ± ±0.14 End count, yarns/cm Spacing p, mm, in cross ± ± ± 0.46 sections from the end count Crimp height h, mm 1.84 ± ± ± 0.30 Weft Linear density, tex (one strand) d1, mm 0.78 ± ± ± 0.16 d2, mm, in cross-sections 3.92 ± ± ± 0.33 on the surface 3.58± ± ± 0.15 Pick count, yarns/cm Spacing p, mm, in crosssections 6.78 ± ± ± 0.35 from the picks count Crimp height, mm 0.25 ± ± ± 0.33 Fabric Thickness of the fabric 3.8 ± ± ± 0.2 Areal density, g/sq m Note: ± gives standard deviation of 10 measurements Figure 6 Cross-sections of Fabric 1: warp (above), weft (below)

11 11 Figure 7 Cross-sections of Fabric 2: warp (above), weft (below) Figure 8 Cross-sections of Fabric 3: warp (above), weft (below)

12 12 4 COMPRESSION TESTS ON THE FABRICS 4.1 Measurement technique Tests were done on the Instron machine, under the speed of 1 mm/min. The sample was placed on a special adjustment table to ensure the alignment of the compressing plates (diameter 35 mm). The stiffness of the machine was accounted for using a force-displacement diagram without the sample (Figure 9). Three compression cycles were tested for each sample. One, two (and four for the fabric 3) layers of each fabric were tested y = x R 2 = F, kn x-x0, mm Figure 9 Force-displacement diagram without a sample (Instron), x0 corresponds to the moment of first contact of the upper and bottom plates (changed from series to series of tests) The fabrics cannot be laid absolutely flat on the plates of the machine. This leads to the fact that the machine registers compressive force well before the distance between the plates reaches the fabric thickness, shown in Table 3 (Figure 10). If this happens, then in the presentation of the results below, only data below the fabric thickness are retained. h, mm layer st 2nd 3rd Figure 10 Compression diagrams, 1 st, 2 nd and 3 rd cycles, fabric 1. Arrow shows the fabric thickness, measured on the cross-sections

13 Results Fabric 1 h, mm layer 1st 2nd 3rd h, mm layers 1st 2nd 3rd Figure 11 Fabric 1. Compression diagrams: Comparison of the compression cycles nd cycle h, mm, per layer nd cycle 1 layer 2nd 2 layers 2nd h, mm, per layer layer 2nd 2 layers 2nd Figure 12 Fabric 1. Compression diagrams: Nesting effect: almost non-existent

14 Fabric 2 h, mm layer 1st 2nd 3rd h, mm layers 1st 2nd 3rd Figure 13 Fabric 2. Compression diagrams: Comparison of the compression cycles h, mm, per layer layer 2nd 2 layers 2nd 2nd cycle h, mm, per layer layer 2nd 2 layers 2nd 2nd cycle Figure 14 Fabric 2. Compression diagrams: Nesting effect: approximately 0.1 mm at the highest compression

15 Fabric 3 h, mm layer 1st 2nd 3rd h, mm layers 1st 2nd 3rd layers 1st 2nd 3rd h, mm Figure 15 Fabric 3. Compression diagrams: Comparison of the compression cycles h, mm, per layer layer 2nd 2 layers 2nd 4 layers 2nd 2nd cycle h, mm, per layer layer 2nd 2 layers 2nd 4 layers 2nd 2nd cycle Figure 16 Fabric 3. Compression diagrams: Nesting effect: approximately 0.05 mm at the highest compression

16 16 5 MECHANICS OF THE YARNS 5.1 Tension Tensile tests were performed in Centexbel lab on the Instron machine at a speed of 10 mm/min and maximum force 200 N. Samples of length 200 mm were used. The diagrams are averages of 3 5 tests on each yarn. The results are shown in Table 4 and Figure 17, Figure 18, Figure 19. Comparison of the tensile diagrams reveals an interesting result (Figure 20): thicker (2400 tex) yarns from fabric 1 show lower initial resistance then the thinner (1870 tex) yarns from fabrics 2 and 3. This might be explained by the higher misalignment and crimp of the fibres in the former case; however, the scatter of the data is quite large, and the difference between the curves lies inside the scatter. Table 4 Tensile diagrams of the yarns from fabrics 1-3 Fabric 1, 2400 tex Fabric 2, 1870 tex Fabric 3, 1870 tex ε, % F, N ε, % F, N ε, % F, N Fabric ave 3 excluded F, N eps, % Figure 17 Tensile diagram of yarns from the fabric 1(one strand 2400 tex).

17 F, N Fabric ave eps, % 4 Figure 18 Tensile diagram of yarns from fabric 2 (one strand 1870 tex). 200 F, N Fabric ave eps, % 4 Figure 19 Tensile diagram of yarns from fabric 3 (1870 tex).

18 yarns from fabric 1, 2400 tex yarns from fabric 2, 1870 tex 200 yarns from fabric 3, 1870 tex 150 F, N eps, % Figure 20 Comparison of the average tensile diagrams of the yarns 5.2 Bending Experimental technique The measurement of the bending resistance is a measurement of dependence of bending moment on curvature of the sample. The KES-F equipment, which has been used, provides paper plots of the bending curves (see Appendix). The plots are processed using the following formula of the KES-F manual: B = a Y SW1 SW 2 where B is the bending rigidity of the sample, N mm 2 ; a, cm is the difference of the vertical readings of the plot at curvatures 0.5 and 1.5 cm -1 (a characterises the corresponding difference in the bending moment; the plot scale is maintained by the equipment in a way which makes the formula valid); Y, SW1 and SW2 are the settings of switches on the machine and the plotter. Measurement of heavy rovings presents some difficulties. To cope with them, measurements were performed on the second bending cycle. The behaviour in the first cycle shows large abnormalities, which are explained by the process of adjustment of a heavy roving to the deformation. Notably the third cycle is very close to the second. The second cycle data is felt to describe the actual behaviour of the rovings inside a fabric more adequately, as the yarn is subject to bending deformations of changing sign prior to the moment when it acquires the final shape.

19 Results a b c Figure 21 KES-F bending diagrams of the yarns. Settings of the KES-F: SW1=5, SW2=1, X=0.2, Y=0.5. Yarns from (a) fabric 1; (b) fabric 2, x2; (c) fabric 3 Table 5 Bending rigidity and bending histeresis of the yarns Yarns from the fabric Linear density, tex B, N mm 2 HB, N mm 5.3 Compression ± ± ± ± ± ± Experimental technique The measurement of the compression resistance is a measurement of dependence of the compression load on the position of the compression head. The maximum load used on KES-F equipment is 100 gf. The compression head is rectangular 4x4 mm. The equipment provides a paper plot of the compression curve.

20 Based on the same reasoning as for bending measurements, the second compression cycle was used. The readings of the sample thickness (position of the compression head vis-à-vis the bottom plate) were read from the plot for the load values 2.5, 5, 10, 20, 40, 60, 80 and 100 gf, and the obtained values were averaged for all the samples of a fabric/roving. As it is evident from the compression curves below, it is impossible to directly read the value of the thickness at zero load. It was computed for each curve by linear extrapolation for the thickness values for the load of 2.5 and 5 gf Results 20 Figure 22 Compression diagrams, yarns from fabric 1: Raw data. Scale of the thickness axis is 1:5 (0.1 mm on the axis = 0.5 mm in reality) d1, mm P, kpa Figure 23 Compression diagram, yarns from fabric 1. Points measurements, thick line averaged diagram

21 21 Figure 24 Compression diagrams, yarns from fabric 2: Raw data. Scale of the thickness axis is 1:5 (0.1 mm on the axis = 0.5 mm in reality) d1, mm P, kpa Figure 25 Compression diagram, yarns from fabric 2. Points measurements, thick line averaged diagram.

22 22 Figure 26 Compression diagrams, yarns from fabric 2: Raw data. Scale of the thickness axis is 1:5 (0.1 mm on the axis = 0.5 mm in reality) d1, mm P, kpa Figure 27 Compression diagram, yarns from fabric 3. Points measurements, thick line averaged diagram.

23 eta1 = d1/d Fabric 1 Fabric 2 Fabric Figure 28 Comparison of the compression coefficients of the yarns from the different fabrics. The behaviour is very similar