TOOLED THICK COMPOSITES by ARVEN H. SAUNDERS III ...

More documents

Recommendations

Info

Temperature (C) 250 200 150 100 50 8552 Flexbeam Typical Cure Cycle with 0.25C/min ramp rates 0 0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960 Time (min) 54 ToolTemp ThickMid MidMid ThinMid MaxTDelta Figure 4.3. Conventional Approach using Two Temperature Dwells. In the second attempt, additional dwell temperatures were added at 100, 120, 140, prior to the 177°C dwell. This attempt, summarized in Fig ure 4.4, yielded obvious violations of the constraints: a maximum temperature of 175°C, with a maximum temperature difference within the laminate of 54°C. Again, this was an unacceptab le cure process. 4.4 Thermal Cycle Optimization Approach The second objective of this research was to apply the model within an optimization scheme to determine the most time-efficient cure cycle processes. Optimizing the cure of a thick laminate differs considerably from a thin laminate often cited in the literature, for which the conduct of its cure is relatively straightforward. The interactions of temperature ramp rates, current laminate degree of cure and its resulting reaction rate were found to be highly complex. Given the thickness of the 8552 flexbeam, in seeking to increase temperature as rapidly as possible in order to shorten overall cure process time, significant temperature differences were
Temperature (C) 200 180 160 140 120 100 80 60 40 20 0 8552 Flexbeam Typical Cure Cycle 0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 960 1020 1080 Time (min) 55 ToolTemp ThickMid MidMid ThinMid MaxTDelta Figure 4.4. Second Attempt at Thermal Cycle Using Multiple Dwells. incurred within the laminate. Therefore there can exist major differences in degree of cure and cure rate within local regions of the laminate. At the thick end, the maximum temperature difference exists. The thinner other end has the 2 nd most temperature difference, followed <strong>by</strong> the thinnest mid-length region. Keeping the maximum temperature within the laminate within a few degrees requires that the temperature ramp rate be small, significantly extending the overall cure cycle time. Because of the sensitivity of the material to exotherm and loss of control, a self-directed approach using the cure rate was selected to seek optimization of this process. This approach varies the tool temperature rate, upon which the laminate temperature depends, subject to the maximum temperature difference within the part. A future cure rate was assessed for various future times before settling on 90 minutes ahead as the most useful. The algorithm projects out into the future the current temperature rate to arrive at a future laminate temperature. A
Page 1 and 2:
PROCESS MODELING SYSTEM FOR PRESS C
Page 3 and 4:
ACKNOWLEDGEMENTS This dissertation
Page 5 and 6:
TABLE OF CONTENTS ACKNOWLEDGEMENTS
Page 7 and 8:
4. RESULTS ........................
Page 9 and 10:
4.7 Acceptable IM7/3501-6 Flexbeam
Page 11 and 12:
CHAPTER 1 INTRODUCTION 1.1 Backgrou
Page 13 and 14: Inspection and evaluation technique
Page 15 and 16: Figure 1.3. Fiber/Layer Waviness in
Page 17 and 18: CHAPTER 2 REVIEW OF RELATED RESEARC
Page 19 and 20: greatly lag in temperature. As a re
Page 21 and 22: Physics-based models are often used
Page 23 and 24: equation above can be solved by wri
Page 25 and 26: keep the cure on track. Examples of
Page 27 and 28: (Chen, 2002). However, because they
Page 29 and 30: during cure and consolidation. In a
Page 31 and 32: initially in the cure process but w
Page 33 and 34: Figure 3.1. Generic Flexbeam with T
Page 35 and 36: Permeability describes the resistan
Page 37 and 38: patterns velocity and timing during
Page 39 and 40: S ii 2 f r = 4k ii ( 1− V where r
Page 41 and 42: proportion of the applied pressure
Page 43 and 44: At any timestep in the simulation,
Page 45 and 46: constant displacement ramp followed
Page 47 and 48: 6 5 4 3 2 1 0 Figure 3.8. Model Con
Page 49 and 50: decrease for CVs that were previous
Page 51 and 52: total resin volume rate for the lam
Page 53 and 54: series electrical circuits—a left
Page 55 and 56: hold these values, with R(k) being
Page 57 and 58: • Resin pressure causes resin flo
Page 59 and 60: where α is cure, An is the pre-exp
Page 61 and 62: temperature conditions. The princip
Page 63: cycle. The ability to optimize temp
Page 67 and 68: Temperature (C) 200 180 160 140 120
Page 69 and 70: useful; as pointed out by Cirisciol
Page 71 and 72: Flexbeam (z) Height and Tool Lid Po
Page 73 and 74: 55 minutes into the S2/8552 cycle,
Page 75 and 76: Resin Pressure (Pa) 1.2E+06 1.0E+06
Page 77 and 78: -7.138E-12 -7.138E-12 -6.517E-12 -5
Page 79 and 80: keeping the level below a certain t
Page 81 and 82: feedback to set the temperature cur
Page 83 and 84: (Chen, 2002) Chen, Y., "Modeling of
Page 85 and 86: (Mitra, 2009) Mitra, K., Majumder,
Page 87 and 88: (Walia, 2006) Walia, R., Shan, H.,
show all

TOOLED THICK COMPOSITES by ARVEN H. SAUNDERS III ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?