Chapter III Experimental Program
4.2 Aluminum Honeycomb Structure Fatigue Test Result
Fatigue test conducted after all static tests finished. Fatigue test also conducted with the same condition as static test conditions.
4.2.1 Aluminum Honeycomb Structure Fatigue Test Result for 100%RH and 10 weeks of immersion
In each condition of fatigue test conducted in several load, such as in 100%RH in 10 weeks immersion time, experiment were conducted in five differences load level those are 50%, 55%, 60%, 65% and 70% and the results were obtained from the experiments for this condition: in 50% load level is
2151.707 N of the load value and 1,000,000 number of cycle, in 55% load level the aluminum honeycomb specimen fractured is 2366.877 N at 468,117 cycles. In 60% load level the aluminum honeycomb specimen fractured is 2582.048 N at 100.824 cycles. In 65% load level the aluminum honeycomb specimen fractured is 2797.219 at 44.765 cycles. In 70% load level the aluminum honeycomb specimen fractured is 3012.39 N at 26,150 cycles. These results could be seen in Table 4.3 and as shown in S-N curve in Figure 4.10. In this condition some of the specimen fracture due to adhesive debonding, as shown in Figure 4.11, which shows sample of the photograph of the aluminum honeycomb structures damaged.
4.2.2. Aluminum Honeycomb Structure Fatigue Test Result for 100%RH and 12 weeks of immersion
In condition 100%RH and 12 weeks of immersion, fatigue tests were also conducted in five differences load level, in 55%, 60%, 65%, 70% and 75%. In 55% load level at maximum load 2117.66 N, the specimen did not fracture until 1,000,000 cycles. For 60% load level, aluminum honeycomb structure fractures at load 2541.192 N and at 425,879 cycles. At 65% load level, aluminum honeycomb structure fracture is 2752.958 N at 410,712 cycles. At 70% load level, the aluminum honeycomb structure fracture is 2964.724 N at 122,228 cycles. At 75%
load level, the aluminum honeycomb structure fracture is 3176.49 N at 43,882 cycles. This fatigue data also could be seen in Table 4.4 and also as shown in Figure 4.12. This figure shows graph of S-N curve of the aluminum honeycomb structure in condition 100%RH and 12 weeks immersion. In this condition, most of aluminum honeycomb structure fracture due to core shear failure as shown in Figure 4.13, which shows a sample of the photograph of fractured aluminum honeycomb structure.
4.2.3 Aluminum Honeycomb Structure Fatigue Test Result for 100%RH and 14 weeks of immersion
For conditions 100%RH and 14 weeks immersion time, fatigue tests were also conducted in five differences load level as same as with 100%RH and 12 weeks immersion conditions, those are 55%, 60%, 65%, 70% and 75% of load level. At 55% of load level, aluminum honeycomb structure did not fracture until 1,000,000 cycles at 2302.299 N. At 60% load level, aluminum honeycomb structure fracture at 2511.597 N at 263,982 cycles. At 65% load level, aluminum honeycomb structure fracture at 2720.897 N at 175,085 cycles. At 70% load level, aluminum honeycomb structure fracture at 2930.197 N at 72,139 cycles. At 75%
load level, aluminum honeycomb structure fracture at 3139.494 N at 64,341 cycles. This fatigue results also could be seen in Table 4.5. In Figure 4.14, shows S-N curve of fatigue data of the aluminum honeycomb structure in condition 100%RH and 14 weeks immersion and in Figure 4.15 shows the photograph of an aluminum honeycomb structure specimen, which is show the consequence of the fractured to aluminum honeycomb structure in 100%RH and 14 weeks immersion time conditions. It shows that core shear failure caused fracture to aluminum honeycomb structure in conditions 100%RH and 14 weeks immersion.
In Figure 4.16 shows the combination graphs of the S-N curve for the aluminum honeycomb structure. In these graphs show the differences of the fatigue test results from different conditions 100%RH and 10 weeks, 100%RH and 12 weeks and 100%RH and 14 weeks. It shows significant changes occur on the strength of the aluminum honeycomb structures in the range of conditions 100%RH for 10 weeks and 14 weeks immersion time.
Figure 4.17 shows the combination of the load level and cycles to failure of the aluminum honeycomb structure. The graph looks similar with the graph in figure 4.16, but in this graph shows the differences of the load level at difference conditions. Figure 4.18 shows the differences of the stroke range () against cycles to failure (Nf) of the aluminum honeycomb structure.
Table 4.1 Data of Static Strength for Aluminum Honeycomb Specimen in 50%
Humidity (as-received) Ultimate Static Strength,
F (N)
Mean Ultimate Static Strength, F (N)
2094.435 2231.775 2172.915 2192.535
Table 4.2 Data of Static Strength of Aluminum Honeycomb Structure in 100%RH Time of
Immersion, (weeks)
Static Ultimate Strength, F (N)
Mean of Static Ultimate Strength, F (N) 2164.82
2142.44 10
2192.87
2166.71 2013.65
2110.89 12
2228.45
2117.64 2013.54
2194.55 14
2070.91
2092.99
Table 4.3 Fatigue Data of Aluminum Honeycomb Structure in Conditions 100%RH and 10 Weeks Immersion Time
Load level Maximum Load, F (N)
Cycle to failure, Nf (cycle)
50% 2151.707 > 1,000,000
55% 2366.877 468,117
60% 2582.048 100,824
65% 2797.219 44,765 70% 3012.39 26,150
Table 4.4 Fatigue Data of Aluminum Honeycomb Structure in Conditions 100%RH and 12 Weeks Immersion Time
Load level Maximum Load, F (N)
Cycle to failure, Nf
(cycle)
55% 2117.66 > 1,000,000
60% 2541.192 425,879
65% 2752.958 410,712
70% 2964.724 122,228
75% 3176.49 43,882
Table 4.5 Fatigue Data of Aluminum Honeycomb Structure in Conditions 100%RH and 14 Weeks Immersion Time
Load level Maximum Load, F (N)
Cycle to failure, Nf (cycle)
55% 2302.299 > 1,000,000
60% 2511.597 263,982
65% 2720.897 175,085
70% 2930.197 72,139 75% 3139.494 64,341
Different Levels of Humidity and Immersion Time
0 500 1000 1500 2000 2500
Maen U ltim a te Stren gt h , F (N )
2172.92 2166.71
2117.64 2092.99
as-recieved 100%RH, 10 weeks
100%RH,
12 weeks 100%RH, 14 weeks
Figure 4.1 Graphs of the different of mean ultimate static strength.
Figure 4.2 Aluminum Honeycomb Structure in different condition. Front view:
(a) 50%RH 0 week immersion, (b) 100%RH 10 weeks immersion, (c) 100%RH 12 weeks immersion, (d) 100%RH 14 weeks immersion.
Side view: (e) 50%RH 0 week immersion, (f) 100%RH 10 weeks immersion, (g) 100%RH 12 weeks immersion, (h) 100%RH 14 weeks immersion.
d
a b c
e f g h
Figure 4.3 Damaged Aluminum honeycomb structure in conditions 100%RH and 10 weeks of immersion time after static test.
Figure 4.4 Damaged Aluminum honeycomb structure in conditions 100%RH and 12 weeks of immersion time after static test.
Figure 4.5 Damaged aluminum honeycomb structure in conditions 100%RH and 14 weeks of immersion time after static test.
Figure 4.6 Graph of static strength of aluminum honeycomb structure in 100%RH and 10 weeks immersion time.
0 500 1000 1500 2000 2500
Lo ad ; F (N )
0 0.4 0.8
Displace
1.2 1.6 2
ment; (mm)
Figure 4.7 Graph of static strength of aluminum honeycomb structure in 100%RH and 12 weeks immersion time.
0 0.4 0.8 1.2 1.6
Displacement;
2
(mm)
0 500 1000 1500 2000 2500
Lo ad ; F (N )
Figure 4.8 Graph of static strength of aluminum honeycomb structure in 100%RH and 14 weeks immersion time.
0 0.4 0.8 1.2 1.6
Displacement;
2
(mm)
0 500 1000 1500 2000 2500
Lo ad ; F (N )
Figure 4.9 Graph of static strength of aluminum honeycomb structure in 100%RH in10 weeks, 12 weeks and 14 weeks immersion time.
0 0.4 0.8 1.2 1.6
Displacement; (mm)
2 0
500 1000 1500 2000 2500
Loa d; F (N )
100%RH 10 weeks 100%RH 12 weeks 100%RH 14 weeks
Figure 4.10 S-N curve of aluminum honeycomb structure in 100%RH and 10 weeks immersion time.
1x105 1x106
Cycles to Failure; Nf (Cycles)
1000
Maximum Load; Fmax (N)
1800
100%RH-10 Weeks
Figure 4.11 Damaged aluminum honeycomb structure in conditions 100%RH and 10 weeks of immersion time after fatigue test.
Figure 4.12 S-N curve of aluminum honeycomb structure in 100%RH and 12 weeks immersion time.
1x105 1x106
Cycles to Failure; Nf (Cycles)
1000
FMaximum Load; max (N)
1800
100%RH-12 Weeks
Figure 4.13 Damaged aluminum honeycomb structure in conditions 100%RH and 12 weeks of immersion time after fatigue test.
Figure 4.14 S-N curve of aluminum honeycomb structure in 100%RH and 14 weeks immersion time.
1x105 1x106
Cycles to Failure; Nf (cycles)
1000
Ma x im u m Lo ad; F
max(N )
1800
100%RH - 14 weeks
Figure 4.15 Damaged aluminum honeycomb structure in conditions 100%RH and 14 weeks of immersion time after fatigue test.
Figure 4.16 S-N curves of aluminum honeycomb structures with various immersion times.
1x105 1x106
Cycles to Failure; N
f(Cycles)
1000
Ma xim u m Lo ad; F
max(N)
1800
100%RH - 10 weeks 100%RH - 14 weeks 100%RH - 12 weeks
1x105 1x106
Cycles to Failure; N
f(cycles)
L oa d Le v e l (% )
75
70
65
60
55
50
100%RH 10 weeks 100%RH 12 weeks 100%RH 14 weeks
Figure 4.17 Graph of the influence of load level (%) on the cycles to failure (cycles) of aluminum honeycomb structures with different immersion times.
Figure 4.18 Graph of relationships between the stroke range (∆) and cycles to failure (Nf) of aluminum honeycomb structures with different immersion times.
0 0.4 0.8 1.2 1.6
Str o k e Range ; (mm )
1x105 2x1
Cycles to
05 3x105 4x105 5x105
Failure; N
f(cycles)
100%RH 1 100%RH 12 100%RH 1
0 weeks weeks 4 weeks
Load level = 60%
CHAPTER V
CONCLUSIONS, CONTRIBUTIONS AND SUGGESTIONS