표제지
목차
ABSTRACT 9
Ⅰ. 서론 10
1. 연구 배경 10
2. 연구 목적 및 논문 구성 12
1) 연구 목적 12
2) 논문 구성 13
Ⅱ. I-fiber 스티칭 공법 및 시편 제작 13
1. I-fiber 스티칭 공법 13
2. 시편 제작 15
Ⅲ. 파손 모니터링 시스템 제작 19
1. AE를 통한 파손 신호 검출 회로 제작 19
2. 전기저항법을 통한 파손 신호 검출 회로 제작 21
3. 모니터링 시스템 제작 22
Ⅳ. 시험 및 파손 모니터링 결과 23
1. 시험 set-up 23
2. 시험 결과 24
1) 16ply 시험 결과 24
2) 32ply 시험 결과 26
3) 64ply 시험 결과 28
4) 시험 결과 분석 30
3. 파손 모니터링 결과 31
1) 16ply 파손 모니터링 결과 31
2) 32ply 파손 모니터링 결과 32
3) 64ply 파손 모니터링 결과 33
4) 파손 모니터링 결과 분석 34
Ⅴ. 유한요소해석 35
1. 유한요소 모델링 35
2. 경계조건 부여 36
3. 해석 결과 37
1) Ref 해석 결과 37
2) 64ply_45° 스티칭 해석 결과 38
Ⅵ. 결론 41
참고문헌 42
Table 1. Material properties of USN-125B and H2550 16
Table 2. Test matrix 17
Table 3. Material properties of epoxy resin in FEM 36
Table 4. Substep and CZM parameter 38
Fig. 1. Composite material 10
Fig. 2. Composite material appliance 10
Fig. 3. Conventional stitching method 14
Fig. 4. Process of I-fiber stitching method 14
Fig. 5. Before and after curing I-fiber 14
Fig. 6. I-fiber stitching machine 15
Fig. 7. Specimen geometry 16
Fig. 8. Stitching pattern 17
Fig. 9. Mold for each thickness of single-lap joint specimen 18
Fig. 10. Schematics of autoclave vacuum bag process 18
Fig. 11. Stitched angle of I-fiber 19
Fig. 12. Filter of each channel 20
Fig. 13. Schematics and electric circuit of AE 20
Fig. 14. Schematic of applied electrical resistance method 21
Fig. 15. Schematics and electric circuit of electrical resistance method 22
Fig. 16. Code of failure monitoring system 22
Fig. 17. AE sensor with pre-amp and data acquisition device 23
Fig. 18. Test set-up 24
Fig. 19. Load-displacement curve of 16ply_Ref specimens 24
Fig. 20. Load-displacement curve of 16ply_0° specimens 25
Fig. 21. Load-displacement curve of 16ply_45° specimens 25
Fig. 22. Reinforcing effect of the new stitching process in 16ply cases 26
Fig. 23. Load-displacement curve of 32ply_Ref specimens 26
Fig. 24. Load-displacement curve of 32ply_0° specimens 27
Fig. 25. Load-displacement curve of 32ply_45° specimens 27
Fig. 26. Reinforcing effect of the new stitching process in 32ply cases 28
Fig. 27. Load-displacement curve of 64ply_Ref specimens 28
Fig. 28. Load-displacement curve of 64ply_0° specimens 29
Fig. 29. Load-displacement curve of 64ply_45° specimens 29
Fig. 30. Reinforcing effect of the new stitching process in 64ply cases 30
Fig. 31. Load transfer concentration of single-lap joint specimens 30
Fig. 32. Failure mode of stitched specimens 31
Fig. 33. Failure monitoring result of 16ply cases with AE method 32
Fig. 34. Failure monitoring result of 16ply cases with electrical resistance method 32
Fig. 35. Failure monitoring result of 32ply cases with AE method 33
Fig. 36. Failure monitoring result of 32ply cases with electrical resistance method 33
Fig. 37. Failure monitoring result of 64ply cases with AE method 34
Fig. 38. Failure monitoring result of 64ply cases with electrical resistance method 34
Fig. 39. Schematics of 1/8 modeling 35
Fig. 40. Modeling for FEM 36
Fig. 41. Boundary condition of single-lap joint FEM 37
Fig. 42. Load-displacement curve of 64ply_Ref test and FEM 37
Fig. 43. Mode I test result and stiffness 38
Fig. 44. Spring element connection and node coupling 39
Fig. 45. Load-displacement curve of 64ply_45° test and FEM 40