C orrelations between damage initiation thresholds in textile - PowerPoint PPT Presentation

C orrelations between damage initiation thresholds in textile composites and fatigue life limits Stepan V. Lomov, Valter Carvelli, Ignaas Verpoest Department MTM – Katholieke Universiteit Leuven Department of Structural Engineering – Politecnico di Milano TexComp 10 - 25 October 2010 1 1

C ontents 1. Tension-tension fatigue of textile composites 2. Acoustic emission monitoring of damage in textile composites 3. Relation between the static damage thresholds and fatigue limit 4. Conclusion TexComp 10 - 25 October 2010 2 2

1. Tension-tension fatigue of textile composites 2. Acoustic emission monitoring of damage in textile composites 3. Relation between the static damage thresholds and fatigue limit 4. Conclusion TexComp 10 - 25 October 2010 3 3

Test methods: tension-tension fatigue F Load-controlled (MTS, Schenk) R = 10 f = 6…10 Hz TexComp 10 - 25 October 2010 4

S -N curve stress, MPa 500 450 glass/epoxy plain weave laminate 400 I 350 300 250 II 200 150 III 100 50 0 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 number of cycles TexComp 10 - 25 October 2010 5

P rogressive damage fatigue at load 140 MPa TexComp 10 - 25 October 2010 6

1. Tension-tension fatigue of textile composites 2. Acoustic emission monitoring of damage in textile composites 3. Relation between the static damage thresholds and fatigue limit 4. Conclusion TexComp 10 - 25 October 2010 7 7

Q uasi static tension 500 1.E+10 2D-24 1.E+09 400 1.E+08 1.E+07 stress, MPa 300 1.E+06 AE 1.E+05 200 1.E+04 stress-strain 1.E+03 100 AE events 1.E+02 AE cumulative 0 1.E+01 0 0.5 1 1.5 2 2.5 3 3.5 strain, % � 1 � 2 1.E+04 1.E+09 cumulative AE energy energy 1.E+08 energy of 5.E+03 events 1.E+07 b AE energy 0.E+00 1.E+06 strain, % Displacement-controlled � 1 0 0.2 0.4 0.6 0.8 1 1.E+05 1.E+08 tension (Instron) � min 1.E+04 � 2 AE energy Acoustic emission (Vallen) 1.E+03 5.E+07 1.E+02 Strain-mapping (LIMESS) 0 0.2 0.4 0.6 0.8 1 c 0.E+00 strain, % a strain, % 0 0.2 0.4 0.6 0.8 1 TexComp 10 - 25 October 2010 8

D amage at the threshold loads 500 1.E+10 2D-24 1.E+09 400 1.E+08 1.E+07 stress, MPa 300 1.E+06 AE 1.E+05 200 1.E+04 stress-strain 1.E+03 100 AE events � 1 1.E+02 AE cumulative 0 1.E+01 0 0.5 1 1.5 2 2.5 3 3.5 strain, % � 2 TexComp 10 - 25 October 2010 9

A re the damage thresholds and the fatigue life connected? stress, MPa 500 450 400 350 300 250 200 150 100 50 0 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 number of cycles TexComp 10 - 25 October 2010 10

1. Tension-tension fatigue of textile composites 2. Acoustic emission monitoring of damage in textile composites 3. Relation between the static damage thresholds and fatigue limit 4. Conclusion TexComp 10 - 25 October 2010 11 11

G lass/epoxy composites TexComp 10 - 25 October 2010 12

P lain weave glass/epoxy Fatigue life limit corresponds to the initiation of the AE events [Lomov, Bogdanovich et al, Comp A, 2009] [Carvelli, Lomov, Bogdanovich et al, CSTE, 2010] TexComp 10 - 25 October 2010 13

3D woven glass/epoxy Fatigue life limit corresponds to the initiation of the AE events [Lomov, Bogdanovich et al, Comp A, 2009] [Carvelli, Lomov, Bogdanovich et al, CSTE, 2010] TexComp 10 - 25 October 2010 14

C arbon/epoxy composites TexComp 10 - 25 October 2010 15

3D woven carbon/epoxy 1000 maximum fatigue stress, MPa 900 800 700 600 500 400 300 200 100 0 1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 fatigue cycles Fatigue life limit corresponds to the onset of strong AE events [Karahan, Lomov, Bogdanovich et al, Comp A, 2009] TexComp 10 - 25 October 2010 16

N C F carbon/epoxy Fatigue life limit is well above the onset of strong AE events [Vallons, Lomov et al, Comp A, 2009] TexComp 10 - 25 October 2010 17

N C F carbon/epoxy, structurally stitched Fatigue life limit is well above the onset of strong AE events [Carvelli, Lomov et al, CSTE, 2010] TexComp 10 - 25 October 2010 18

3D carbon/epoxy braid 1400 1.00E+08 1.00E+07 1200 1.00E+06 1000 1.00E+05 stress, MPa 800 1.00E+04 600 1.00E+03 400 1.00E+02 200 1.00E+01 0 1.00E+00 0 0.002 0.004 0.006 0.008 0.01 0.012 strain Fatigue life limit is well above the onset of strong AE events [Carvelli, Lomov, Bogdanovich et al] TexComp 10 - 25 October 2010 19

1. Tension-tension fatigue of textile composites 2. Acoustic emission monitoring of damage in textile composites 3. Relation between the static damage thresholds and fatigue limit 4. Conclusion TexComp 10 - 25 October 2010 20 20

S ummary: fatigue limit vsdamage initiation threshold � _ULT: failure carbon/epoxy braid NCF carbon/epoxy, 3D carbon/epoxy stitched � _2: initiation NCF carbon/epoxy, unstitched of high energy damage NCF carbon/epoxy events � _1: damage initiation plain weave glass/epoxy � _min: first 3D glass/epoxy AE event TexComp 10 - 25 October 2010 21