Ultrasound inspections on glass fiber/phenolicresin and on carbon fiber/epoxy resin composites during flexural fatigue. V. G. García

534 views

Published on

Published in: Business, Lifestyle
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
534
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
8
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Ultrasound inspections on glass fiber/phenolicresin and on carbon fiber/epoxy resin composites during flexural fatigue. V. G. García

  1. 1. Ultrasound inspections on glass fiber/phenolicresin and on carbon fiber/epoxy resin composites during flexural fatigueV.G. García, J. Sala, L. Crispí, J.M. Cabrera, A. Istúriz, A. Sàez, M. Millán, C. Comes, D. Trias Composites
  2. 2. 1. Introduction: Outline2. Experimental Procedure: Materials inspected and tested Ultrasound equipment Ultrasound visualization software 4-Point bending fatigue tests3. Results: Wöhler plot Ultrasound scans at N=10,000 cycles Ultrasound scans at N=12,000 cycles A fracture at N=13,344 cycles4. Conclusions 2/18
  3. 3. 2. Experimental Procedure Fig. 1. Dimensions of the glass fiber/phenolic resin bars Fig. 3. Ultrasound inspections every 2,000 cycles. Until 20,000 Fig. 2. Dimensions carbon fiber/epoxy resin bars cycles. Fig. 4. 4-Point bending flexural fatigue. 3/18
  4. 4. 2. Experimental Procedure: Materials inspected and tested The Glass Fiber Reinforced Polymer (GFRP) was Isovid G-3 manufactured by Composites Ate. -Isovid G-3 consists of 200g/m2 plain weave E-glass, and a modified phenolic resin that enhances flame retardant characteristics. -Layers are 0.10 to 0.11mm thick. -All plies were stacked to match 0º and 90º. -Composite was high speed milled to reach dimensions. Fig. 5. GFRP samples. Fig. 6. GFRP sample after Fig. 7. Woven appearance. exposure to sun light. 4/18
  5. 5. 2. Experimental Procedure: Materials inspected and testedThe Carbon Fiber Reinforced Polymer (CFRP) was manufactured using Hexcel 8552/32%/134/IM7(12K) at the INTA Materials and Structures Department. -The 8552/32%/134/IM7(12K) pre-impregnated carbon fiber plies consisted of tows of 12,000 individual fibers of IM7 intermediate modulus carbon. Fig. 8. CFRP samples. -The pre-preg contained 32% of 8552, an amine cured, toughened epoxy resin system. -The nominal ply thickness was 134µm. -Measured ply thickness was 129µm to 134µm. Table 1. Stacking sequences and percentages of layers oriented 90º, 0º or ±45º. % % % % # Specimens Stacking sequence 90º 0º 45º -45º layers [(0/±45/02/±45/02/90) / ( CFRP-P011 8.8 54.4 18.4 18.4 283 02/±45/02/±45/02/90)12]S [(0/90) / ( Fig. 9. Smooth, rough, and CFRP-P021 9.5 54.7 17.9 17.9 201 02/±45/02/±45/02/90)9]S machined surfaces of CFRP [(0/90/0/±45/02/90) / ( samples. CFRP-P041 11.9 54.2 16.9 16.9 59 02/±45/02/±45/02/90)2]S 5/18
  6. 6. 2. Experimental Procedure: Ultrasound equipment -A single crystal longitudinal wave transducer of 1MHz and 13mm diameter was used for most inspections. -The gain was set at 5dB. -Specimens CFRP-P041 were inspected using a 5MHz (10mm diameter) transducer at 5dB. -Acoustic wave propagation was set at 3275m/s. -Mapro developed a software, based on LabView, to process the pulse-echo signals and visualize A-scans,Fig. 10. Ultrasound equipment built by Mapro B-scans, C-scans, plus optional ∫-scans. using a Socomate USPC3100LA card. Y (Index) X (scan) Fig. 11. A pulse-echo inspection in an Fig. 12. Before an inspection the Fig. 13. Inspection of immersion bath. transducer is positioned at the (0,0) a GFRP specimen. origin. 6/18
  7. 7. 2. Experimental Procedure: Ultrasound visualization software Fig. 14. Screen image of the visualization software, after loading the ultrasound signal data. 7/18
  8. 8. 2. Experimental Procedure: Ultrasound visualization softwareFig. 15. Screen image after: digitally aligning the first peak, positioning the cut off lines, and setting a color range. 8/18
  9. 9. 2. Experimental Procedure: Ultrasound visualization software Fig. 16. In this study the scale of the signal intensity (potence %) and cut off lines were set as shown above. 9/18
  10. 10. 2. Experimental Procedure: Ultrasound visualization software Interface (I) echo Back-wall (B) echo Fig. 17. In this study the A-scans was passed through different algorithms to create alternative scan images. 10/18
  11. 11. 2. Experimental Procedure: Ultrasound visualization software C-scan minus I & B ∫-scan with I&B ∫-scan minus I & B ∫-scan with I & B minus mean ∫-scan minus I & B minus mean Fig. 18. A menu in the C-scan label allows processing the A-scan to create different ∫-scans. 11/18
  12. 12. 2. Experimental Procedure: Ultrasound visualization software Fig. 19. Filtered A-scan has less peaks. 12/18
  13. 13. 2. Experimental Procedure: 4-Point bending fatigue tests Flexural Stress The maximum strength σ0 σ = (3FL)/(4Wh2) for the GFRP was F→ force, 391MPa, and for the L → support length, CFRP was 1135MPa. W → specimen width, h → specimen thickness. Normalized fatigue stresses L for GFRP specimens was F F set at 0.2 to 0.9 and for the Fig. 21. GFRP specimen tested until 2 2 CFRP specimens at 0.36 to fracture to determine σ0. 0.60. F L S L F Normalized fatigue stress is 2 4 4 2 defined as σ0 / σmax where LFig. 20. Loading diagram σmax is the maximum flexural according to ASTM fatigue stress in the outer D6272-02 (2008). layers. L Fig. 22. CFRP specimen tested until fracture to determine σ0. 13/18
  14. 14. 3. Results: Wöhler plot 600 400 Maximum stress, σmax (MPa) GFRP-P011-40-1000-38_1/3 GFRP-P031-40-710-16_2/6 CFRP-P011-40-1440-38_1/2 Maximum stress, σmax (MPa) 400 CFRP-P011-40-1440-38_2/2 300 GFRP-P011-40-1000-38_2/3 GFRP-P011-40-1000-38_3/3 GFRP-P031-40-710-16_3/6 GFRP-P031-40-710-16_4/6 CFRP-PO21-40-1040-27_1/2 GFRP-P021-40-1000-27_1/3 GFRP-P031-40-710-16_5/6 200 GFRP-P021-40-1000-27_2/3 GFRP-P031-40-710-16_6/6 200 f = 0,8 Hz CFRP-P021-40-1040-27_2/2 GFRP-P021-40-1000-27_3/3 GFRP-P041-40-307-8_1/2 R=0,1 CFRP-P041-40-307-8_2/2 100 GFRP-P031-40-710-16_1/6 GFRP-P041-40-307-8_2/2 0 0 2 4 6 8 10 12 14 16 18 20 0 0 2 4 6 8 10 12 14 16 18 20 Number of cycles (x1000) -200 Number of cycles (x1000) -100 4-point bending tests -400 -200 -600 -300 4-point bending tests f = 0,8 Hz -400 R = 0,1 -800 Fig. 23. Maximum stresses during fatigue Fig. 24. Maximum stresses during fatigue every 2,000 cycles for the CFRP specimens. every 2,000 cycles for the GFRP specimens. 400 Maximum stress, σmax (MPa) 350 300 4-point bending 250 fatigue tests, 235 MPa 200 R=0,1 150 f=0,8Hz 13,344 cycles 100 Isovid G-3: 50 Plain weave 200g/m2 fiber glass with flame retardant phenolic resin 0 101 102 103 100104 105 Number of cycles to failure, N Fig. 25. Maximum stresses versus cycles to failure of Isovid G-3 GFRP. 14/18
  15. 15. 3. Results: Ultrasound scans at N=10,000 cycles Fig. 26. Specimen GFRP-P031-40-710-16_4/6 inspected only between the white lines. A-scan with the interface (I) and back-wall (B) echoes. C-scan minus I & B ∫-scan with I & B ∫-scan minus I & B ∫-scan with I & B minus mean ∫-scan minus I & B minus Fig. 27. At N=10,000 cycles. Fig. 28. At N=10,000 cycles with mean signal filter. Without filtering the A-scan. After filtering the A-scan. 15/18
  16. 16. 3. Results: Ultrasound scans at N=12,000 cycles Fig. 29. The triangle in specimen GFRP-P031-40-710-16_4/6 points to the damaged area found in the scans. C-scan minus I & B ∫-scan with I & B ∫-scan minus I & B ∫-scan with I & B minus mean ∫-scan minus I & B minus Fig. 30. At N=12,000 cycles. Fig. 31. At N=12,000 cycles with mean signal filter. Without filtering the A-scan. After filtering the A-scan. 16/18
  17. 17. 3. Results: A failure at N=13,344 cycles (a) (b) (c) (d) Fig. 32. Specimen GFRP-P031-40-710-16_4/6 after fracture at N=13,344 cycles. 17/18
  18. 18. 4. Conclusions -The additional information (i. e. newer spots) provided by the ∫-scans still require further corroboration with the actual internal damage. -However, these algorithms allow revealing both superficial and internal damage in one single scan, and ultimately may improve damage detection of composite materials. -The fatigue behavior of a glass fiber/phenolic resin composite was characterized by means of a partial Wöhler plot. -CFRP specimens only showed superficial damage after the fatigue tests of this study. 18/18
  19. 19. Thank you for your attention.

×