Effect of Cure Temp Variations

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Effect of Cure Temperature Variations on Moisture Absorption and Hygrothermal-Mechanical Properties for Out-of-Autoclave Polymer Composites ADMRC Project Year-End Presentation 12-20-10 PI: Bob Minaie, Ph.D. Department of Mechanical Engineering

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Slide230: 

EFFECT OF CURE TEMPERATURE VARIATIONS ON MOISTURE ABSORPTION AND HYGROTHERMAL-MECHANICAL PROPERTIES FOR OUT-OF-AUTOCLAVE POLYMER COMPOSITES ADMRC Project Year-End Presentation 12-20-10 PI: Bob Minaie, Ph.D. Department of Mechanical Engineering Wichita State University (316) 978-5613 bob.minaie@wichita.edu

Outline of the Presentation: 

2 Outline of the Presentation Introduction Material and cure cycles Viscoelastic properties of 5320 8HS Mechanical properties of 5320 8HS Thermal properties of 5320 8HS Physical properties of 5320 8HS Void morphology Correlations and observations Summary Future work

Objective: 

3 Objective

Technical Approach: 

4 Technical Approach [1] Cure Samples in Rheometer and DSC Select Materials and Cure Cycles Obtain Hot/Wet and Dry Mechanical Properties and Tg Find Correlation Between State of Cure and Mechanical Properties Develop Quality Control Guidelines Cure Panels in Oven Obtain State of Cure Based on Thermal and Rheological Properties

Material: 

Material 5

Cytec Recommended Cure Cycle for 5320 8HS: 

Cytec Recommended Cure Cycle for 5320 8HS 6

Cure Cycle Design for 5320 8HS: 

Cure Cycle Design for 5320 8HS 7

Degree of Cure (DOC) for Different Cure Cycles for 5320 8HS: 

Degree of Cure (DOC) for Different Cure Cycles for 5320 8HS 8

Viscoelastic Properties: 

Viscoelastic Properties

Cure Cycles Used for Curing Samples in Rheometer for 5320 8HS: 

Cure Cycles Used for Curing Samples in Rheometer for 5320 8HS 10

Storage Modulus during Cure for Different Cure Cycles for 5320 8HS: 

Storage Modulus during Cure for Different Cure Cycles for 5320 8HS 11 Plateau was achieved for the samples post cured at 290F, 260F, and 240F Low Viscosity Region

Loss Modulus and Tanδ during Cure for Different Cure Cycles for 5320 8HS: 

Loss Modulus and Tanδ during Cure for Different Cure Cycles for 5320 8HS 12 Vitrification Point Gel Point

Gel Time and Vitrification Time for Different Cure Cycles for 5320 8HS: 

Gel Time and Vitrification Time for Different Cure Cycles for 5320 8HS 13

Dry and Wet Glass Transition Temperature (Tg) for Different Cure Cycles for 5320 8HS: 

Dry and Wet Glass Transition Temperature (Tg) for Different Cure Cycles for 5320 8HS 14 Wet Tg Samples were exposed to boiling water for 48 hours.

Mechanical Properties: 

Mechanical Properties

Panel Layup for 5320 8HS: 

Panel Layup for 5320 8HS 16 y x z

Cure Cycles for 5320 8HS Panels: 

Cure Cycles for 5320 8HS Panels 17 Cure Cycles for Post Cure Temperature Variation Study Cure Cycles for Debulking Time Variation Study

Mechanical and Physical Properties of 5320 8HS: 

Mechanical and Physical Properties of 5320 8HS 18

Machining Layout and Vacuum Bag Scheme for 5320 8HS: 

Machining Layout and Vacuum Bag Scheme for 5320 8HS 19

C-Scan of the Panels for 5320 8HS:Effect of Debulking Time Variation: 

C-Scan of the Panels for 5320 8HS: Effect of Debulking Time Variation 20

C-Scan of the Panels for 5320 8HS:Effect of Post Cure Temperature Variation: 

C-Scan of the Panels for 5320 8HS: Effect of Post Cure Temperature Variation 21

Room Temperature Short Beam Shear (SBS) Strength and Failure Modes for Different Cure Cycles for 5320 8HS: 

Room Temperature Short Beam Shear (SBS) Strength and Failure Modes for Different Cure Cycles for 5320 8HS 22 Failure mode for specimens post cured at 290oF: Interlaminar Shear and Compression Failure mode for all other specimens post cured from 210oF to 260oF: Interlaminar Shear

Room Temperature Combined Loading Compression (CLC) Strength and Failure Modes for Different Cure Cycles for 5320 8HS: 

Room Temperature Combined Loading Compression (CLC) Strength and Failure Modes for Different Cure Cycles for 5320 8HS 23 Failure mode for specimens post cured at 210oF: Long Splitting in the Gage Section (SGV) Failure mode for all other specimens post cured from 220oF to 290oF: Delamination in the Gage Section (DGV) and Kink Bands in the Gage Section (KGV)

CLC Failure Modes for Samples Post Cured at 210oF and 290oF for 5320 8HS: 

24 CLC Failure Modes for Samples Post Cured at 210oF and 290oF for 5320 8HS Specimen Post Cured at 210oF Specimen Post Cured at 290oF

Room Temperature CLC Modulus and Poisson’s Ratio for Different Cure Cycles for 5320 8HS: 

Room Temperature CLC Modulus and Poisson’s Ratio for Different Cure Cycles for 5320 8HS 25

Thermal Properties: 

Thermal Properties

Thermal Properties of Cured Prepreg for Different Cure Cycles for 5320 8HS: 

Thermal Properties of Cured Prepreg for Different Cure Cycles for 5320 8HS 27

Thermal Stability Obtained with Thermogravimetric Analysis (TGA) for Different Cure Cycles for 5320 8HS: 

28 Thermal Stability Obtained with Thermogravimetric Analysis (TGA) for Different Cure Cycles for 5320 8HS

Physical Properties: 

Physical Properties

Cured Prepreg Physical Properties for Different Cure Cycles for 5320 8HS: 

30 Cured Prepreg Physical Properties for Different Cure Cycles for 5320 8HS

Void Morphology: 

Void Morphology

Void Morphology for the Panel Post Cured at 290oF for 5320 8HS: 

Void Morphology for the Panel Post Cured at 290oF for 5320 8HS 32

Void Morphology for the Panel Post Cured at 210oF for 5320 8HS: 

Void Morphology for the Panel Post Cured at 210oF for 5320 8HS 33

Correlations and Observations: 

Correlations and Observations

Normalized CLC Strength, SBS Strength, Dry Tg and DOC vs. Post Cure Temperature for 5320 8HS: 

35 Normalized CLC Strength, SBS Strength, Dry Tg and DOC vs. Post Cure Temperature for 5320 8HS

Normalized CLC Strength, SBS Strength, and Dry Tg vs. DOC for 5320 8HS: 

36 Normalized CLC Strength, SBS Strength, and Dry Tg vs. DOC for 5320 8HS

Summary (I): 

37 Summary (I) To study the effect of post cure temperature variation on properties of 5320 8HS, the post cure temperature was varied from 210oF to 290oF while the intermediate cure temperature was kept at 200oF. Five 13'x13' panels with stacking sequence of [0,+45]3s were cured in an oven at different post cure temperatures. The same cure cycles were used to cure prepreg samples in the DSC and rheometer. Viscoelastic, thermal, physical and room temperature mechanical properties were obtained for the studied cure cycles for 5320 8HS. To obtain room temperature mechanical properties of 5320 8HS, short beam shear (SBS) and combined loading compression (CLC) tests were performed. The average SBS and CLC strength gradually decreased as the post cure temperature decreased. The average CLC modulus and Poisson’s ratio did not vary significantly with post cure temperature. Dry Tg and degree of cure of the samples also gradually decreased as the post cure temperature decreased.

Summary (II): 

38 Summary (II) A good correlation was observed among CLC Strength, SBS Strength, Dry Tg, and DOC. Room temperature SBS failure mode was different for different cure cycles: For specimens post cured at 290oF: Interlaminar Shear and Compression. For all other specimens: Interlaminar Shear. Room temperature CLC failure mode was different for different cure cycles: For specimens post cured at 210oF: Long Splitting in the Gage Section. For all other specimens: Delamination and Kink Bands in the Gage Section. Porosity of the panels was studied with c-scan and acid digestion. Void morphology was studied with an optical microscope: The panel post cured at 290oF had the least porosity. The observed voids in the panel were both spherical and cylindrical. All panels had acceptable porosity. The observed cylindrical voids were more than the spherical voids for the panels post cured at lower temperatures. The test coupons for moisture diffusivity, wet Tg, and hot/wet mechanical testing are currently being conditioned at 160oF and 85% relative humidity.

Future Work (I): 

39 Future Work (I) Obtain hot/wet mechanical properties of 5320 8HS using short beam shear (SBS), combined loading compression (CLC), and open hole compression (OHC) tests. Obtain moisture diffusivity for different cure cycles for 5320 8HS. Study hot/wet failure mode for SBS specimens and hot/wet and dry failure modes for CLC specimens cured at different cure cycles for 5320 8HS. Study correlation between the viscoelastic properties and the hot/wet mechanical properties of 5320 8HS. Develop quality control guidelines that assure obtaining the required material properties for out-of-autoclave polymer composites.

Future Work (II): 

40 Future Work (II) Study the effect of intermediate cure temperature and heat-up rate variation on moisture absorption and hygrothermal properties of out-of-autoclave prepreg laminates. Study the effect of laminate thickness and lay-up on moisture absorption and hygrothermal properties of out-of-autoclave prepreg laminates. Study the effect of core design on porosity of sandwich panels fabricated with honeycomb core and prepreg face-sheets.

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