Optimization and mechanical response of modular infusion compaction and normalization

Figures & data

Figure 1. Bagging scheme for producing MI compaction barrier, (a) outer bag and (b) inner bag.

Figure 2. Compaction tooling (a) CAD model with front beam hidden and (b) actual set-up.

Figure 3. Set-up in XCT (a) photograph of installation on rotary stage and (b) schematic of vacuum flow.

Figure 4. Sample midplane slices at given process steps (a) inner vacuum: 9.4mbar, outer vacuum: 1013mbar, (b) Inner vacuum: 9.4mbar, outer vacuum: 9.43mbar (c) Inner vacuum: 800mbar, outer vacuum: 9.4mbar, (d) Inner vacuum: 1013mbar, outer vacuum: 9.4mbar, (e) Inner vacuum: 9.4mbar, outer vacuum: 9.4mbar, (f) Inner vacuum: 9.4mbar, outer vacuum: 1013mbar.

Table 1. Sample thickness and void volume measurements at given process steps.

Inner vacuum (mbar)	Outer vacuum (mbar)	Average left thickness (mm)	Average mid thickness (mm)	Average right thickness (mm)	Average void volume (%)
9.4	1013	5.55	4.72	5.84	0.11%
9.4	9.4	5.11	5.24	5.33	0.34%
200	9.4	5.16	5.13	5.32	0.33%
400	9.4	5.10	5.21	5.32	0.34%
600	9.4	5.12	5.12	5.28	0.35%
800	9.4	5.20	5.12	5.29	0.33%
1013	9.4	5.18	4.87	5.33	0.25%
9.4	9.4	5.22	5.20	5.25	1.52%
9.4	1013	5.38	4.94	5.41	1.00%

Figure 5. Significant void volume transitions, (a) volume reference rendering, (b) initial state scan, (c) first notable void volume change, (d) large void pocket presented under the laminate, (e) void volume upon restoration of vacuum pressure, (f) void volume when caul p[late actuating outer bag vacuum is released.

Figure 6. Flexural test parent panel, (a) non-optimized process C-scan, (b) optimized process C-scan, and (c) optimized process time of flight thickness analysis.

Figure 7. Time of flight thicknesses across the center of the optimized panel.

Table 2. Flexural test sample measurements.

Sample	Test	Length (mm)	Width (mm)	Thickness (mm)	Support span (mm)	Support ratio
Compacted 1	3PB	176.5	13.01	3.94	124.8	32:1
Compacted 2	3PB	176.5	13.02	3.94	124.8	32:1
Compacted 3	3PB	176.5	13.02	3.95	124.8	32:1
Compacted 4	3PB	176.5	13.02	3.97	124.8	32:1
Compacted 5	3PB	176.5	13.02	3.98	124.8	32:1
Compacted 7	4PB	176.5	13.04	4.01	156	40:1
Compacted 8	4PB	176.5	13.02	3.99	156	40:1
Compacted 9	4PB	176.5	13.03	3.99	156	40:1
Compacted 10	4PB	176.5	13.06	3.96	156	40:1
Compacted 11	4PB	176.5	13.04	3.95	156	40:1
Baseline 1	3PB	176.5	13.02	4.01	124.8	32:1
Baseline 2	3PB	176.5	13.02	4.02	124.8	32:1
Baseline 3	3PB	176.5	13.01	4.03	124.8	32:1
Baseline 4	3PB	176.5	13	4.02	124.8	32:1
Baseline 5	3PB	176.5	13.02	4.01	124.8	32:1
Baseline 7	4PB	176.5	13	4.02	156	40:1
Baseline 8	4PB	176.5	13.02	4.01	156	40:1
Baseline 9	4PB	176.5	13.04	4.03	156	40:1
Baseline 10	4PB	176.5	13.03	4.02	156	40:1
Baseline 11	4PB	176.5	13.03	4.04	156	40:1

Figure 8. Flexural test set-up.

Figure 9. Three-point bend flexural strength results.

Figure 10. Four-point bend flexural strength results.

Figure 11. Three-point bend chord moduli.

Figure 12. Four-point bend chord moduli.

Figure 13. Three-point bend strain fields at 481 N loading (a) compacted example, (b) baseline example, (c) average strain and standard deviation at given position.

Figure 14. Four-point bend strain fields at 481 N loading (a) compacted example, (b) baseline example, (c) average strain and standard deviation at given position.

Table A1. XCT parameters and explanation of settings.

Setting	Value	Explanation
Energy (kVp)	210	Higher energy X-rays penetrate samples with greater ease, at the cost of image contrast. Lower energy may result in noisier images as fewer X-rays arrive at the detector because of attenuation within the sample.
Current (µA)	176	High currents provide a greater X-ray photon count with less noise but also increases focal spot size which reduces image resolution.
Exposure per frame (ms)	67	Short exposure leads to increased noise, however, short exposures are critical to minimizing scan time.
Frames per projection	1	Several frames can be acquired and averaged but at the penalty of longer scan times.
Number of projections	1571	The total number of radiographs recorded during scanning, one per angular position.
Projection size (px)	1000 × 1000	Results from the 2 × 2 times binning of the detector elements; binning can enable faster detector speeds manifesting as shorter exposure time per frame [36].
Source to sample distance (mm)	315.12	The focus to object distance (FOD) and focus to detector distance (FDD) distances control geometrical magnification (M) and therefore resolution. Given M = FDD/FOD and FDD should be minimized to reduce noise, it is desirable to have the smallest FOD possible.
Source to detector distance (mm)	1572.56
Reconstructed voxel size (mm)	0.08	The resolution achieved by the chosen scan settings.
Scan time (seconds)	105.26	Time required to acquire data for a 3D image reconstruction.

DIC setup parameters are shown in Table A2.

Table A2. DIC parameters.

Experiments	Three-point bend		Four-point bend
Technique used	3D digital image correlation
	Camera 1	Camera 2	Camera 1	Camera 2
Sensor and digitization	2448 × 2050, 12-bit
Camera noise (% of range)	0.021%	0.021%	0.021%	0.021%
Lens and imaging distance	100mm F2.8 Tokina ATI-X lens, 0.53 m
Frame rate	1 Hz
Pixel to mm conversion	1 pixel = 0.014 mm		1 pixel = 0.014 mm
ROI (mm)	30 × 13 mm		30 × 13 mm
Subset, step	69, 45
Interpolation, shape functions, correlation criterion	Bicubic (6^th order spline), affine, ZNSSD
Pre-smoothing	None
Displacement resolution	9.33E-04mm		1.1E-03mm
Strain
Smoothing technique	Local polynomial – affine least-squares fit
Strain window	1 data point
Window area	353,682 pixels
Strain resolution	33.69µε		32.62µε

DIC camera noise floor study Tables A3 and A4.

Table A3. Three-point bend noise floor study.

Sample	Image 1 (µε)	Image 2 (µε)
B1	25.29	25.38
B2	31.28	31.26
B3	28.30	28.26
B4	36.71	36.30
B5	75.36	75.25
C1	28.29	28.45
C2	24.11	24.08
C3	23.67	23.73
C4	25.76	35.59
C5	33.31	33.39
Average	33.69

Table A4. Four-point bend noise floor study.

Sample	Image 1 (µε)	Image 2 (µε)
B10	46.18	46.09
B11	39.78	39.92
B6	41.85	42.07
B7	30.39	30.39
B8	37.80	37.92
B9	35.88	36.01
C10	30.64	29.99
C11	22.67	22.71
C6	29.70	29.93
C7	26.14	26.16
C8	25.69	25.73
C9	24.68	24.69
Average	32.63

Baek J, Pineda AR, Pelc NJ. To bin or not to bin? The effect of CT system limiting resolution on noise and detectability. Phys Med Biol. 2013;58(5):1433–1446. doi: 10.1088/0031-9155/58/5/1433.

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