SAMPE Journal - January/February 2013 - (Page 51)

Figure 5. Rheology profile of NONA-001 resin in NONA cure cycle. Figure 6. Thermal profile of the fabrication of a NONA part on 1-inch thick foam tooling board. of the final CFRP tool. There are various options for finishing and sealing the tooling board surface. The carbon fabric of the CFRP tool is laid up on the MM and infused with NONA resin. A rapid NONA cure is performed, and the tool is demolded from the MM. Since an oven will be used for part fabrication regardless, a free-standing post-cure may be performed to ensure dimensional stability of the tool. The tool may also be machined and resealed if the dimensional tolerances are not met. See Figure 4 for a schematic of the process. There are several key questions that need to be answered. How will the CTE of the foam MM affect dimensional tolerances? How will the foam surface be properly sealed? How durable is the foam MM surface? How robust is the NONA resin matrix upon numerous thermal cycles and chemical attack of prepreg and infusion resins? How dimensionally stable is the NONA tool after NONA cure and/or after a post-cure? Regarding the effect of the CTE, CRG believes that NONA composite processing offers a distinct advantage over other methods because of the snap cure-like process. When the NONA resin vitrifies, the temperature of the foam tool lags significantly. A rheology trial mimicking the NONA cure shows the viscosity profile over time (Figure 5). For this specific temperature profile and 10 rad/s frequency, CRG estimated a gelation temperature of 69°C (tand = 1) and a vitrification temperature of 92°C (onset of complex viscosity). CRG records the temperature of the NONA part and tooling board at multiple locations to monitor the cure conditions. Fig- ure 6 shows empirical temperature data from the NONA cure of a 20-ply carbon composite on one-inch thick tooling board. The figure shows the temperature profile for the thermocouple (TC) at the center of the part and under the tool at the center of the part. The infusion occurs at 10 minutes of total time. Table 3 lists the temperatures taken from the rheology experiment associated with gelation, vitrification, and maximum temperature reached. It is likely that the cure events occurred before the times and temperatures selected since more time has passed in the NONA experiment than in the rheology run. According to the data, the bottom of the tool temperature is 35.5°C at the time of part vitrification. At this point, it can be assumed that the part has locked in its final dimensions. For simplicity, one could assume that the average temperature of the foam tool is 63.8°C (average of 92.0°C at top and 35.5°C at bottom), although it is likely less, being a dynamic thermal conduction process. The total change in temperature of the tool foam is 38.8°C (63.8 – 25.0). Assuming the current tooling board has a high CTE of 50x10-6/°C, the dimensional change would be 1938 μm/m. In comparison, the Cycom™ 5215 OOA tooling prepreg system has a two hour cure (not including time to heat and cool the tooling) at 127°C, giving a total change in temperature of 102°C (127 – 25). Conventional tooling materials require slow temperature ramps to encourage consistent curing throughout the laminate, rather than from the bag side and in, potentially trapping volatiles. Tools made of aluminum, stainless steel 304, Invar 36, Invar 42, or the same tooling board as in NONA Table 3. Estimated cure events during NONA cure of 20-ply CFRP part. SAMPE Journal, Volume 49, No. 1, January/February 2013 51

Table of Contents for the Digital Edition of SAMPE Journal - January/February 2013

SAMPE Journal - January/February 2013
Contents
President's Message
Technical Director's Corner
Materials & Products
Welcome SAMPE’s Newest Members
SAMPE LinkedIn Communities
SAMPE 2013|Long Beach
SAMPE Proceedings
Perspectives
Europe News & Views
SAMPE Journal Editorial Calender
SAMPE Europe’s SEICO 2013, Paris, France
SAMPE Europe’s SETEC 13 Wuppertal, Germany
Corporate Partners
Industry News
The SAMPE Foundation
SAMPE Tech 2012-A Review
SAMPE Tech 2012-Photo Gallery
SAMPE Tech 2013|Wichita, KS Call for Papers
SAMPE China 2012-A Review
SAMPE China-Photo Gallery
Advertiser’s Index
Resource Center
SAMPE Membership Application
SAMPE Books & CD’s Order Form
Industry Events Calendar
Chapter Contacts

SAMPE Journal - January/February 2013