AUTOMATED SOLUTION TO HIGH VOLUME MANUFACTURING USING LOW-COST PCM TOWPREG

Transcription

1 AUTOMATED SOLUTION TO HIGH VOLUME MANUFACTURING USING LOW-COST PCM TOWPREG

2 Prepreg Compression Molding Process (PCM) Automation-ready molding process Preforming by press operation Compression molding removes the necessity for expensive autoclave Laminate Heating Preforming Net Shape Charge Compression Preform Molding Demold Use standard hot presses already used in the industry 2

3 Material development Rapid cure prepreg Reduce cure time as low as 3 minutes at 150 C (300 F) Viscosity vs Temperature Resin optimized for match metal compression molding High viscosity at molding temperature Tg higher than tool temperature High molding pressure Porosity-free Possible Class-A surface finish 3

4 Commercial Application of PCM GT-R 2014 (Factory option) GT-R NISMO Awarded SPE 2014 Most Innovative Composite Part SPE Plastics 2015 Quality of Life Award 4

5 Prepreg Limitations Laminate Heating Preforming Net Shape Charge Compression Preform Molding Demold 5

6 What is AFP/ATL? Automated Fiber Placement Automated Tape Layup Computer controlled robots capable of depositing dry or pre-impregnated fibers on a tool to replace hand layup. Repeatable Scalable Minimize Waste Tailored fiber orientation Slow rates High capital Expensive raw material 6

7 New machine developments High Speed Flat Laminate Builder Low cost, High output Automotive Industry Requirements - Production friendly - Small foot print - 2m x 2m layup area - Manageable capital investment - Minimum 30 kg/hr - 16 lanes BA Composite s STAXX Compact

8 Conventional AFP Raw Material Traditionally use SLIT TAPE made from prepreg Precise width (+/- 0.13mm) Any areal weight Extra processing Increased waste Increased cost $$ 30%+ 8

9 Towpreg alternative Same requirements as PCM - Epoxy resin system optimized for compression molding - Press curable with minimum flow - 3-5min cure cycle C Tg Additionally - Use low cost 24K or 50K dry fiber - Available in 6.3mm (1/4 ) and 12.6mm (1/2 ) bandwidths - Width control +/-0.3mm - Cost competitive - Rigid, dry resin at room temperature - Easily tackyfies under heat - Volatile free resin system Traditional Towpreg process 9

10 First Towpreg Placement Trial Towpreg (34-700; 24K/NX092713) FAW (gsm) 256 R.C. (%) 34.0 RAW (gsm) 132 PAW (gsm) 388 Vf (%) 56.4 Thickness (mm)

11 Preforming Flat Laminate Heat the laminate to 70 for 1 minute The laminate becomes drapable. Press forming to near-net shape. Pressure of 0.2 MPa Immediately cool down the preform (1 minute) Net Shape Preform 11

12 Scrap Rate Reduction Fabric or Prepreg >20% Waste Reduction Towpreg Placement Near Net Shape Laminate 12

13 Compression Molding Molding Condition Tool temperature; 150 Molding pressure; 4MPa Cure time; 7 minutes Highest molding pressure created dry lines in the final part Up to 9% flow observed at 4MPa molding. Want ~2% Limiting molding pressure using stops gave better looking parts Must reduce resin flow should to achieve PCM quality part 13

14 Limiting the resin flow Aging in oven prior to molding Laminated towpreg Make preform Aging in a oven at 80 After aging 14

15 Limiting the resin flow Aging in oven prior to molding #1: no Aging Resin flow : 6.1% Too much resin flow #2: Aging : 80 x 1 hr Resin flow : 2.1% Optimized resin flow #3: Aging : 80 x 3 hr Resin flow : 0.2% Aged too much Aging in a oven reduced surface defects and resin flow 1 hour at 80 reduced flow to ~ 2%. The surface of parts looks good Fiber distortion was minimal Over Aging material ) creates fiber distortion and defects 15

16 Laminate Evaluation Top Layer: 90 deg Macro-photograph Layers are evenly distributed and any gaps have been filled in the pressing process. 16

17 Confirming Mechanical Properties Panel #1 Panel #2 17

18 Making a Large Part Technical feasibility study carried out with molds used in commercial production 1. Material Preparation 2. Preform 3. Trimming 4. Aging 5. Press Molding 6. Molded parts 18

19 Larger Part Layup Trial Lay-up Simple, smooth finish part 0/90/0/90/0 cross ply 1.26mm thickness Complex geometry part 0/90/0 cross ply 0.76mm thickness Fiber direction ; 0deg Black line shows near net shape plus 30mm excess trim material. White line is net shape. 19

20 Larger Part Molding Trial Molding trial was performed with similar pre-forming and molding conditions as those used in production parts. Some changes were necessary based prior experimentation. Preforming Heating to 70 Press forming pressure; 0.2 MPa Preforming cycle; totally 7 minutes Aging 30 min at 80 to reduce resin flow Compression Molding Tool Temperature; 150 Molding pressure; 4 MPa (Simple shape) 7 MPa (Complex shape) Cure time; 7 minutes 20

21 Simple Shape with Smooth Finish Preform was made similarly to the current production part 21

22 Simple Shape with Smooth Finish A parts with relatively simple geometry and smooth surface finish was successfully molded. Gaps were filled as shown in the molding of the miniature engine hood. 22

23 Complex Shape Macrophotograph (next slide) Enhanced drapability of the towpreg laminate improved on baseline results using UD prepreg laminate. 23

24 Complex Shape Each towpreg stretched independently. 24

25 Improved Drapability Prepreg tends to fold Wrinkles occur during press preforming UD prepreg Independent tows can shear Shear allows part to stretch during preform Towpreg 25

26 Improved Drapability Towpreg UD prepreg 26

27 Molded Complex Shape Part Gap between towpreg was bigger than in outer skin. But the large gaps were filled with resin and fiber from inner layers. Successful molding of a part that cannot be molded with traditional prepreg. 27

28 Cost model Molded Part Cost Break Down (Cost/part) Material Resin Preparation ATP Process Preform Cost Index Cut off scrap Molding Finishing Prepreg Fabric+Resin Towpreg PCM RTM ATP/PCM Cost model defined for 50,000 parts per year using standard industry costs 28

29 Conclusion Combination of ATP (Automated Towpreg Placement) and PCM (Prepreg Compression Molding) showed great potential as a high cycle CFRP molding process. Rapid cure Towpreg was optimized for ATP and molded using the PCM process. ATP equipment laid up laminate quickly, efficiently and without any manual operation. Towpreg laminate showed excellent drapability that was suitable for PCM preforming. Part cost was significantly reduced by limiting material scrap. Future development - Reduce resin flow to avoid aging process. - Accelerate cure cycle to 180 seconds to match PCM prepregs - Application-specific development 29

30 Made Possible with the Help of We also deeply appreciate to Nissan Motor Co., Ltd. for a permission to use their molds for this study. 30

31 Thank you!