T Ogasawara et al. Composites Science and Technology 65(2005)2541-2549 110-125 Mirror a Thickness: 1=4 *:k Fixed end Mirror positio Width: b=6or 9 Thickness: t=4.5 Half mirror He-Ne laser Fig 4. Specimen configuration and dimensions used for the experi- ments:(a)tensile test, (b) torsional test. Mirror a strain gauges(gauge length 5 mm)which were bonded on both of the specimen surfaces. The displacement rate Scale a was 0.5 mm/min Matrix cracking characteristics under on-axis loading Fig. 5. Schematic configuration of a torsional test: (a)torsional test were investigated for a specimen using the replica film setting,(b)optical lever system( top view) method with surface replicas being taken under load at various stages of the loading cycle 3.3. Torsional test Pulley 1 Specimen configuration and dimensions used for tor- sional tests are shown in Fig. 4(b). Two kinds of speci- mens with different width b(b=6 and 9 mm)were Mirror prepared. The thickness, h, was 4.5 mm. Note that the pecimen width is 2 or 3 times in the size of a fabric unit cell (3 mm) Schematic drawings and photograph of torsional te configuration are shown in Figs. 5 and 6, respectively One end of a specimen was fixed to a base fixture, and Specimen a torsion arm was attached at another end. torsional moment was applied through the torsion arm to the pecimen as shown in Figs 5(a) and 6. A weight (F1) Fig. 6. Photograph showing the torsional test setting. was directly hung at one end of the torsion arm, and weight (F2, FI= F2) was subjected at another end through the pulley 1. Own weight (w)of the specimen determined by measuring the distance between the and torsion arm was cancelled using a weight (w) flected beams. The locations of the mirror points shown through the pulley 2. in Fig. 5(a) reflect the constraint of 0.25 <x/L <0.75 An optical lever system was used for measuring the obtained by the FEA simulation. Torsional rigidity GJ twist angle of the specimen. An optical lever is a conve- is defined as follows make possible an accurate measurement of the displace- G/=M:/o, O=(0A-OB)/d, ment. Two small mirrors were put at the point A and b where d is the distance between two mirrors(50 mm) on the specimen upper surface as shown in Figs. 5(a) Applied torsion moment was between 0. 2 and 0. 8 Nm. and 6 He-Ne laser beams were irradiated to the mirrors It was preliminarily confirmed that microcrack propaga as shown in Fig. 5(b), and torsion angles 0a, OB were tion never occur under the torsional momentstrain gauges (gauge length 5 mm) which were bonded on both of the specimen surfaces. The displacement rate was 0.5 mm/min. Matrix cracking characteristics under on-axis loading were investigated for a specimen using the replica film method with surface replicas being taken under load at various stages of the loading cycle. 3.3. Torsional test Specimen configuration and dimensions used for tor￾sional tests are shown in Fig. 4(b). Two kinds of speci￾mens with different width b (b = 6 and 9 mm) were prepared. The thickness, h, was 4.5 mm. Note that the specimen width is 2 or 3 times in the size of a fabric unit cell (3 mm). Schematic drawings and photograph of torsional test configuration are shown in Figs. 5 and 6, respectively. One end of a specimen was fixed to a base fixture, and a torsion arm was attached at another end. Torsional moment was applied through the torsion arm to the specimen as shown in Figs 5(a) and 6. A weight (F1) was directly hung at one end of the torsion arm, and a weight (F2, F1 = F2) was subjected at another end through the pulley 1. Own weight (w) of the specimen and torsion arm was cancelled using a weight (w) through the pulley 2. An optical lever system was used for measuring the twist angle of the specimen. An optical lever is a conve￾nient device to magnify a small displacement and thus to make possible an accurate measurement of the displace￾ment. Two small mirrors were put at the point A and B on the specimen upper surface as shown in Figs. 5(a) and 6. He–Ne laser beams were irradiated to the mirrors as shown in Fig. 5(b), and torsion angles hA, hB were determined by measuring the distance between the re- flected beams. The locations of the mirror points shown in Fig. 5(a) reflect the constraint of 0.25 < x/L < 0.75 obtained by the FEA simulation. Torsional rigidity GJ is defined as follows: GJ ¼ Mt=x; x ¼ ðhA
hBÞ=d; ð4Þ where d is the distance between two mirrors (50 mm). Applied torsion moment was between 0.2 and 0.8 N m. It was preliminarily confirmed that microcrack propaga￾tion never occur under the torsional moment. Mirror A Mirror B Specimen Fixed end Gxy Mt Gzx h F1 F2 b be d θ A θ B A B Half mirror He-Ne laser Mirror B Mirror A Scale B Scale A a b Fig. 5. Schematic configuration of a torsional test: (a) torsional test setting, (b) optical lever system (top view). 120 b Width: b = 6 or 9 Thickness: t = 4.5 (mm) Mirror position 35 Fiber orientation: 110 ∼ 125 10 Thickness: t = 4 (mm) Fiber orientation 0 /90 : ±45 : a b Fig. 4. Specimen configuration and dimensions used for the experi￾ments: (a) tensile test, (b) torsional test. Fig. 6. Photograph showing the torsional test setting. 2544 T. Ogasawara et al. / Composites Science and Technology 65 (2005) 2541–2549