1. Lab Directive Research and Development Conductive Foam Characterization and Cyanate Ester Testing B. COFFEY L. CONNOLLY E. ANDERSSEN J. SILBER 7-11-14

2. Areas of Focus Low Density, thermally conductive (carbon and aluminum) open-cell foam UHV Compatible, Hi-Tg/toughness resins and laminates—compatible with RTM/potting process

3. Airflow Testing Adding conductive foam to the flow has two benefits to heat exchange ◦It increases the area of exchange ◦It increases the effective volumetric conductivity of the flow Foam is specified by Density, Pore Size, and Conductivity ◦Given those as inputs; we should be able to predict effective heat transfer enhancement ◦Density or Void fraction and Pore size should predict pressure drop characteristics Several papers propose models relating the above but are very sensitive to the inputs ◦Need data to start correlating models.

4. What These Foams Actually Look Like 20PPI (Pores per Inch) Al Foam I. Zivkovic, A. Murk Prog in Electro. Research B 2012 30PPI (Pores per Inch) Reticulated Vitreous Carbon Foam Pore Cell

5. Initial Experimental Setup: A Thermal Short Circuit Heat conduction along apparatus affects TC measurements  T of air across sample measure of Q When dragged together by conduction Q ~ 0 Improved isolation, both separation and insulating pipes

6. A Modified Approach A new test setup is being constructed this week To improve repeatability, sample “cartridges” are being manufactured, each with its own TC and heater coil A larger separation between the sample and manometer ports should prevent a thermal short circuit Longer samples are being prepared to access different Reynolds numbers New setup switches from aluminum to PVC and PE tubing to avoid conduction with TCs

7. Interest in CE Resins CE resins useful for HEP detectors due to toughness and stability Radiation tolerance and low off-gas/adsorption also interesting Interesting applications: ◦Pot SC Magnet coils—CE may reduce training cycles ◦CE resins we already process may be UHV compatible ◦Everyone wants higher thru thickness conductivity ◦RTM Capability for SC Magnet and larger structures RTM CE has a risk: Uncontrolled thermal runaways ◦RTM resins have low Mol Weight—for low viscosity, require more reaction (trimerization) to fully cure ◦It might catch fire without proper precaution History of some magnet vendors finding this unsafe—mostly smoke, no fire ◦Goal is to find fully safe operating process for resins Therein lies the rub – Cu is the catalyst for CE resins… ◦When talking to Mfg. words like bomb and explosion were thrown around for SuperCon Magnet applications (approx. 2-5kg of resin)

8. Resins Investigated EX 1510 (Tencate Advanced Composites) ◦RTM version of EX1515, close to what we typically process 403 and 425 (Composites Technology Development) ◦403 is pure CE—exotherm curve shown ◦425 is a mixture of CE and Epoxy currently used on ITER ◦403 has extensive testing for radiation tolerance: GGy, but also resin some vendors might want to avoid.

9. Experiment Set-up: Searching for an Exotherm

10. Calorimetry Technique Around 1cc of CE Resin is added to the Cu cup Cu cup is pressed into Vespel insulation. The Vespel is the slip fitted into the aluminum block If TC 6/7 > 2/3 Heat is being generated by resin sample m*Cp*  T with appropriate inputs yields Heat of reaction TC 4/5 used for average T of vespel insulator for H calc Cured sample shown

11. A Typical Mfg. Cure Profile t hold Viscosity min t cure Ramp at ~3degC/min to “gelation” temperature (90-100 degC) Hold at “gelation” temperature Ramp to cure temperature Hold at cure temperature

12. A Typical Experimental Cure Profile T onset TT Ramp at Max recommended rate (~3degC/min) to cure temperature Repeat for different neat resins for baseline T onset,  T Add materials, e.g. SC magnet wire, nano- particles, etc Increased  T means more heat, T onset may be coupled

13. CTD-403 CE Resin Exotherm Linear fit to heater block temp subtracted from Ts/Tv DT of each with m*Cp of appropriate constituents used to calculate energy released -- around 250 Joules in this case Lower than expected, but may not have all energy release channels -- working on a new theoretical model and ANYSYS simulation Vespel Sample Cup

14. EX-1510 (Lack of) Exotherm Attempts to induce an Exotherm by increasing ramp rate and adding copper to the sample have been unsuccessful Will be curing larger neat resin samples (~15g) for tensile testing – will hopefully be able to see an exotherm with the larger sample size

15. Moving Forward Continue improving the consistency and repeatability of the foam experiment and results Accurately characterize the energy release of a sample of neat CE resin exotherming for all resin systems Now that we have proven that the exotherm of the resin is not dangerous, we can start moving faster with production of resin mechanical test pieces and further investigate the affects of embedding SuperCon cable in a resin where copper is the catalyst

17. Foam Characterization Calculate Foam parameters from Pressure Drop Permeability (K) Darcy – Forchheimer Equation (1) Pore Size (2) 1 - J. Bonnet, F. Topin. Flow Laws in Metal Foams: Compressibility and Pore Size Effects. Transp. Porous Media (2008) 75 233-254 2 - J. Despois, A. Mortensen. Permeability of open-pore microcellular materials. Acta Materiala (2005) 53 1381 – 1388.

18. Foam Heat Transfer Model Development for heat transfer through foam filled tube, predicts heat transfer coefficients W. Lu, C.Y. Zhao, S. A. Tassou. Thermal analysis on metal-foam filled heat exchangers. Part I: Metal-foam filled pipes. IJHMT 49 (2006) 2751 – 2761. f fluid w wall b bulk e effective