Materials and Structures (2008)41: 879-890 Fig. 5 Dimensions of glass fiber strap specimens a)Specimens of glass fiber straps without epoxy coating b)specimen of glass fiber strap with poxy coating at grip areas prepared for tensile testin 100mm 100mm 15.8mm c)Specim d)Specime 40 mm 40 mm evenly stretched and evenly held by jaws. However, it 200 mm width is shown in Fig. 8b. At the maximum was difficult to place evenly stretched fibers of wider stress specimen fibers started to fail successively and straps in the testing machine jaws. In the beginning of therefore the stress decreased and the strain increased the stretching, only a few fibers started to stretch, and (see Fig. 6a, b). At the place of specimens failure the "force-strain" diagram had a smaller force most fibers remained stretched and broken but they growth, but a larger growth of the strain. Only after were not broken at the strait cross-section line. The I the fibers were stretched, i.e., above strain of breaking area of fibers in fabric was several centi- approximately 0.3%, the"force-strain" curve meters wide showed a larger force growth and a smaller growth of the strain. Therefore two modules of elasticity were determined, first E. -o3% for strains between 6 Influence of deformation speed on the tensile 0. 1% and 0.3%o as recommended by ASTM [3], and strength and the modulus of elasticity of glass 1-0.5% for strains between 0.1% and 0.5%0 fiber straps The secant stiffness Jo.ax.%(kN/m)according to EN Iso 10319 [5] was measured too. When most of the The second testing was done for the specimen straps fibers broke the extensometer was turned off. after width of 15. 8 mm in order to determine the influence that, the deformation was(automatically)determined of deformation speed on the tensile strength of glass from the distance between the apparatus jaws. fiber straps. The tensile strength was determined for However, the value of deformation resulted from three deformation speeds: (a)2,(b)5, and(c)10 mm the real deformation of a strap to which a small strap min. The results are shown in Table 5. The test slipping in the jaws was added. The measured values results showed that differences of tensile strengths were presented in Table 4. The"force-strain"dia- (max) obtained by different deformation speeds were AsS ams of the 15.8 mm wide specimens are shown in small. It could be concluded that different testing 6a. Figure 6b shows the"force-strain"diagrams speeds did not have a significant influence on the of the specimens with 200 mm width. a photo of the value of the tensile strength of the fabric. The speed specimen of the 15.8 mm wide strap, which was put of deformation of 5 mm/min resulted in the highest in the testing machine, is shown in Fig. 7a. Figure 7b strength of the straps, i.e., 2.6% above average shows a photo of the same specimen(15.8 mm) after strength(see Table 5). This speed also resulted in the failure. A photo of a specimen after failure in Fig. &a most equalized values of the strength, which is of 50 mm width and that of evident from the smallest value of the coefficient ofevenly stretched and evenly held by jaws. However, it was difficult to place evenly stretched fibers of wider straps in the testing machine jaws. In the beginning of the stretching, only a few fibers started to stretch, and the ‘‘force–strain’’ diagram had a smaller force growth, but a larger growth of the strain. Only after all the fibers were stretched, i.e., above strain of approximately 0.3%, the ‘‘force–strain’’ curve showed a larger force growth and a smaller growth of the strain. Therefore two modules of elasticity were determined, first E0.1–0.3% for strains between 0.1% and 0.3% as recommended by ASTM [3], and second E0.1–0.5% for strains between 0.1% and 0.5%. The secant stiffness Jmax 0.1–0.5% (kN/m) according to EN ISO 10319 [5] was measured too. When most of the fibers broke, the extensometer was turned off. After that, the deformation was (automatically) determined from the distance between the apparatus jaws. However, the value of deformation resulted from the real deformation of a strap to which a small strap slipping in the jaws was added. The measured values were presented in Table 4. The ‘‘force–strain’’ dia￾grams of the 15.8 mm wide specimens are shown in Fig. 6a. Figure 6b shows the ‘‘force–strain’’ diagrams of the specimens with 200 mm width. A photo of the specimen of the 15.8 mm wide strap, which was put in the testing machine, is shown in Fig. 7a. Figure 7b shows a photo of the same specimen (15.8 mm) after failure. A photo of a specimen after failure in Fig. 8a shows a specimen of 50 mm width and that of 200 mm width is shown in Fig. 8b. At the maximum stress specimen fibers started to fail successively and therefore the stress decreased and the strain increased (see Fig. 6a, b). At the place of specimen’s failure most fibers remained stretched and broken but they were not broken at the strait cross-section line. The breaking area of fibers in fabric was several centi￾meters wide. 6 Influence of deformation speed on the tensile strength and the modulus of elasticity of glass fiber straps The second testing was done for the specimen straps width of 15.8 mm in order to determine the influence of deformation speed on the tensile strength of glass fiber straps. The tensile strength was determined for three deformation speeds: (a) 2, (b) 5, and (c) 10 mm/ min. The results are shown in Table 5. The test results showed that differences of tensile strengths (fmax) obtained by different deformation speeds were small. It could be concluded that different testing speeds did not have a significant influence on the value of the tensile strength of the fabric. The speed of deformation of 5 mm/min resulted in the highest strength of the straps, i.e., 2.6% above average strength (see Table 5). This speed also resulted in the most equalized values of the strength, which is evident from the smallest value of the coefficient of a) Specimens of glass fiber straps without epoxy coating 2.63 mm 15.8 mm 50 mm 100 mm 450 mm 15.8 mm c) Specimen of glass fiber strap with epoxy coating at its total length 450 mm strengthened with 2 straps and epoxy coating 200 mm 15.8 mm 3 x 50 mm 40 mm ekstensometer 100 mm Direction of the stretching d) Specimen in machine jaws 40 mm 100 mm b) Specimen of glass fiber strap with epoxy coating at grip areas 100 mm 100 mm 150 mm 50 mm 50 mm Fig. 5 Dimensions of glass fiber strap specimens prepared for tensile testing Materials and Structures (2008) 41:879–890 885