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The values obtained from the force histories (X + Sx).

Table 4 The values obtained from the force histories (X + Sx).

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Fig. 1. Production process and geometry of hybrid pipes a) filament winding process b) sample dimensions c) stacking sequence.
Fig. 1. Production process and geometry of hybrid pipes a) filament winding process b) sample dimensions c) stacking sequence.
Properties of fibers and matrix material. Table 1
Properties of fibers and matrix material. Table 1
Fig. 3. Open ended internal pressure test apparatus [73]. “It is seen in Table 3 that, bending stiffness values is approximately equal for each energy level until first damage formation as Hertzian [t is seen in Fig. 7 that when the impact energy level is 5J, th
Fig. 3. Open ended internal pressure test apparatus [73]. “It is seen in Table 3 that, bending stiffness values is approximately equal for each energy level until first damage formation as Hertzian [t is seen in Fig. 7 that when the impact energy level is 5J, th
Fig. 2. Low velocity impact test rig and hydraulic pump [74].
Fig. 2. Low velocity impact test rig and hydraulic pump [74].
As for the second regime, it is seen that the highest resistance to bending is shown by CGG samples while the lowest response in shown by GGC samples. As explained before, placing the carbon fibers at the inner surface of the pipe leads to increase in stiffness of the pipe. On the other hand, Table 3 shows that the slope of the second regime obtained for all specimens increase with increasing impact energy level. How- ever, it is seen that when the impact energy level reaches to 20 J, the slope of the second regime decreases considerably. This is a clear in- dication of damage formation which results in decrease in material's resistance. Fig. 5. Impact force-time variations for different impact energy levels as 5, 10, 15, 20 J. It is seen in Fig. 8 that the lowest rebound energy is measured for GGC specimens. This situation is a clear indication that serious amount of damage has formed within GGC specimens. This situation is also evaluated and verified in damage formation section. It is seen in this figure that kinetic energy transferring characteristics of other
As for the second regime, it is seen that the highest resistance to bending is shown by CGG samples while the lowest response in shown by GGC samples. As explained before, placing the carbon fibers at the inner surface of the pipe leads to increase in stiffness of the pipe. On the other hand, Table 3 shows that the slope of the second regime obtained for all specimens increase with increasing impact energy level. How- ever, it is seen that when the impact energy level reaches to 20 J, the slope of the second regime decreases considerably. This is a clear in- dication of damage formation which results in decrease in material's resistance. Fig. 5. Impact force-time variations for different impact energy levels as 5, 10, 15, 20 J. It is seen in Fig. 8 that the lowest rebound energy is measured for GGC specimens. This situation is a clear indication that serious amount of damage has formed within GGC specimens. This situation is also evaluated and verified in damage formation section. It is seen in this figure that kinetic energy transferring characteristics of other
Fig. 4. Images of hybrid pipes after burn-off test.
Fig. 4. Images of hybrid pipes after burn-off test.
Fig. 6. Maximum contact forces for different impact energies.
Fig. 6. Maximum contact forces for different impact energies.
Fig. 7. Variation of contact force versus displacement for hybrid pipes subjected to different impacts energy levels as 5, 10, 15, 20J A clear delaminated zone around the impact point is seen in Fig. 10. Bending stiffnesses of successive layers are different due to the differ- ence in fiber directions. This situation is the main reason of delami- nation formation with the help of shear stresses as a result of bending [19,100]. It is seen that, the delaminated zone seen at inner surface is larger than that observed at outer surface. The compression/tension The maximum contact force, contact duration, maximum displace- ment, impulse force and absorbed energy values for different experi- mental parameters are presented in Table 4. It is seen in this table that; all quantities increase with increasing impact energy level.
Fig. 7. Variation of contact force versus displacement for hybrid pipes subjected to different impacts energy levels as 5, 10, 15, 20J A clear delaminated zone around the impact point is seen in Fig. 10. Bending stiffnesses of successive layers are different due to the differ- ence in fiber directions. This situation is the main reason of delami- nation formation with the help of shear stresses as a result of bending [19,100]. It is seen that, the delaminated zone seen at inner surface is larger than that observed at outer surface. The compression/tension The maximum contact force, contact duration, maximum displace- ment, impulse force and absorbed energy values for different experi- mental parameters are presented in Table 4. It is seen in this table that; all quantities increase with increasing impact energy level.
Fig. 9. Variation of energy absorption for different impact energies. Fig. 8. Variation of energy transfer versus time under 32 bar internal pressure for different impact energies as 5, 10, 15, 20 J.
Fig. 9. Variation of energy absorption for different impact energies. Fig. 8. Variation of energy transfer versus time under 32 bar internal pressure for different impact energies as 5, 10, 15, 20 J.
Fiber volume fractions of hybrid pipes.
Fiber volume fractions of hybrid pipes.
Bending stiffness values for different regimes (N/m).
Bending stiffness values for different regimes (N/m).
Fig. 10. Low velocity impact macro damage zone formed at GGC hybrid pipe.
Fig. 10. Low velocity impact macro damage zone formed at GGC hybrid pipe.
Fig. 11. SEM images taken from radial cross-sections of specimens tested undet 20 J impact energy a) CGG b) GCG c) GGC.
Fig. 11. SEM images taken from radial cross-sections of specimens tested undet 20 J impact energy a) CGG b) GCG c) GGC.
Fig. 12. SEM images of damage formations at hybrid pipes with CGG stacking sequence.
Fig. 12. SEM images of damage formations at hybrid pipes with CGG stacking sequence.
Fig. 13. SEM images of internal surface matrix cracks formed at CGG hybrid pipes.
Fig. 13. SEM images of internal surface matrix cracks formed at CGG hybrid pipes.
Fig. 16. SEM images of internal surface matrix cracks formed at GGC hybrid pipes.
Fig. 16. SEM images of internal surface matrix cracks formed at GGC hybrid pipes.
Fig. 17. Internal surface matrix cracking and delamination formed during low velocity impact on GGC hybrid pipes.
Fig. 17. Internal surface matrix cracking and delamination formed during low velocity impact on GGC hybrid pipes.
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