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Dr. Penado's Publications

Publications

• F. E. Penado and J. H. Clark III (2009).  "Optimizing the frequency response of a steering mirror mount for interferometry applications."  Proceedings of the 2008 SPIE Conference—The International Society for Optical Engineering:  Advances in Optomechanics, San Diego, California, August 2-6, Vol. 7424, p. 742403.
• J. H. Clark III, F. E. Penado and F. Cornelius (2009).  "Mirror deformation versus contact area in mounted flat mirrors."  Proceedings of the 2008 SPIE Conference—The International Society for Optical Engineering:  Advances in Optomechanics, San Diego, California, August 2-6, Vol. 7424, p. 74240C.
• J. H. Clark III, F. E. Penado, M. DiVitorrio, and J. P. Walton (2008).  “Mount-induced deflections in 8-inch flat mirrors at the Navy Prototype Optical Interferometer.”  Proceedings of the 2008 SPIE Conference—The International Society for Optical Engineering:  Optical and Infrared Interferometry, Marseille, France, June 23-28, Vol. 7013, p. 70133K.
• F. E. Penado, J. H. Clark, III, J. P. Walton, R. C. Romeo, R. N. Martin (2007).  “Calculation of the Elastic Properties of a Triangular Cell Core for Lightweight Composite Mirrors.”  Proceedings of the 2007 SPIE Conference—The International Society for Optical Engineering:  New Developments in Optomechanics, San Diego, California, August 26-30, vol 6665, pp B1-B8.
• P. G. Wood, F. E. Penado, J. H. Clark, III, J. P. Walton (2007).  “Pier Vibration Isolation for Lightweight Interferometry Telescopes.”  Proceedings of the 2007 SPIE Conference—The International Society for Optical Engineering:  New Developments in Optomechanics, San Diego, California, August 26-30, vol 6665, pp L1-L6.
• P. G. Wood, F. E. Penado, J. H. Clark, III, J. P. Walton (2007).  “Design and analysis of a rotationally resistant floor for a telescope enclosure.”  Proceedings of the 2007 SPIE Conference—The International Society for Optical Engineering:  New Developments in Optomechanics, San Diego, California, August 26-30, vol 6665, pp J1-J6.
• J. H. Clark, III, J. P. Walton, F. E. Penado, D. Smith (2007).  “Optical Mount Modifications for Increased Articulation at the Navy Prototype Optical Interferometer.”  Proceedings of the 2007 SPIE Conference—The International Society for Optical Engineering:  New Developments in Optomechanics, San Diego, California, August 26-30, vol 6665, pp 12.1-12.8.
• J. P. Walton, J. H. Clark, III, F. E. Penado (2007).  “Design of Asymmetrically-Loaded End-Plates with Vacuum Seal Surfaces for the Navy Prototype Optical Interferometer.”  Proceedings of the 2007 SPIE Conference—The International Society for Optical Engineering:  New Developments in Optomechanics, San Diego, California, August 26-30, vol 6665, pp 13.1-13.7.
• F. E. Penado, S. T. Broome, R. C. Romeo, R. N. Martin, J. H. Clark, III, J. P. Walton (2006).  “Composite End-Fittings for Lightweight Telescope Applications.”  Proceedings of the SAMPE ’06 Fall Technical Conference, Dallas, Texas, Nov. 6-9, 2006.

• J. R. Andrews, F. E. Penado, S. T. Broome, C. C. Wilcox, S. R. Restaino, T. Martinez, S. W. Teare, F. Santiago (2006).  “Characterization of the Lightweight Telescope Developed for the NPOI.”  Proceedings of the International Society for Optical Engineering (SPIE)--Ground-based and Airborne Telescopes, Orlando, Florida, May 24-31, v 6267 II, p 62673Q.

• F. E. Penado (2006).  “A Computational Procedure for the Determination of Fracture Parameters at Interfacial Contact Cracks in Composite Laminates.”  Journal of Composite Materials, Vol. 40, No. 8, pp 701-715.
• F. E. Penado and J. S. Lindner (2005). "Aeroelastic Modeling and Testing of Small Wind Turbine Blades." Poster presentation at the American Wind Energy Association WINDPOWER 2005 Conference, Denver, Colorado, May 15-18, 2005.
• F. E. Penado (2003). "Fracture Mechanics Analysis of the Contact Crack in Laminated Composites." Proceedings of the 14th International Conference on Composite Materials, ICCM/14, San Diego, California, July 14-18, 2003.
• F. E. Penado, K. Gonzalez-Landis, P. Flikkema, V. Johnson, J. Palais, R. Roedel and D. Shunk (2002). "The Arizona Tri-University Master of Engineering Program." Proceedings of the 32nd ASEE/IEEE Frontiers in Education Conference, Boston, MA, November 6-9, 2002.
• F. E. Penado, M. J. Blendowski and N. J. Glover (2002). "An Evaluation of Failure Criteria for Predicting Biaxial Strength of Laminates." Proceeding of the 9th International Conference on Composites Engineering, ICCE/9, San Diego, California, July 1-6, 2002.
• F. E. Penado (2001). "Out-Of-Plane Coupling Effects on Stress Intensity Factors at Interface Cracks in Composite Lap Joints.” Journal of Thermoplastic Composite Materials, Vol 14, pp 178-200.
• F. E. Penado, P. J. Waydo and T. R. Kornfeld (2001). "Manufacturing of Composite Tubes Using a Simulated Autoclave Technique." Proceedings of the 33rd International SAMPE Technical Conference (ISTC), Seattle, Washington, November 4-8, 2001.
• F. E. Penado (2001). "An Efficient Method for the Analysis of the Interface Crack with a Contact Region." Presented at the Sixth US National Congress on Computational Mechanics, Dearborn, Michigan, August 1-4, 2001.
• F. E. Penado (2001). "Singular Intensity Factors at Bimaterial Anisotropic Interfaces." Composite Structures, Vol 52, pp 323-333.
• F. E. Penado (2000). "Analysis of Singular Regions in Bonded Joints.” International Journal of Fracture, Vol 105, pp 1-25.
• F. E. Penado (2000). "Determination of Stress Intensity Factors in Cracked Bonded Composite Joints.” Journal of Thermoplastic Composite Materials, Vol 13, pp 174-189.
• F. E. Penado (1999). "Stress Singularities in Cracked Bonded Joints with Off-Axis Plies,” Proceedings of the 14th ASC Annual Technical Conference on Composite Materials, Fairborn, OH, September 27-29, 1999.
• F. E. Penado (1998). "Determination of Stress Intensity Factors in Cracked Bonded Joints”. Proceedings of the 13th ASC Annual Technical Conference on Composite Materials, Baltimore, MD, September 21-23, 1998.
• F. E. Penado (1998). "A Simplified Method for the Geometrically Nonlinear Analysis of the Single Lap Joint,” Journal of Thermoplastic Composite Materials, Vol. 11, pp 272-287.
• F. E. Penado (1998). "Structural Composites," in Peter Conley (ed.), Space Vehicle Mechanisms: Elements of Successful Design, John Wiley & Sons, Inc., New York, pp 53-91.
• F. E. Penado (1997). "A Simplified Method for the Geometrically Nonlinear Analysis of the Single Lap Joint”. Proceedings of the 12th ASC Annual Technical Conference on Composite Materials, Dearborn, MI, October 6-8, 1997.
• F. E. Penado (1993). "A Closed Form Solution for the Energy Release Rate of the Double Cantilever Beam Specimen with an Adhesive Layer," Journal of Composite Materials, Vol. 27, No. 4, pp 383-407.
• F. E. Penado and R. K. Dropek (1990). "Numerical Design and Analysis of Bonded Joints," ASM International Engineered Materials Handbook, Vol. 3: Adhesives and Sealants, ASM International, pp 477-500.
• F. E. Penado and E. S. Folias (1989). "The Three Dimensional Stress Field around a Cylindrical Inclusion in a Plate of Arbitrary Thickness," International Journal of Fracture, Vol. 39, pp 129-146.
• Ibid., Structural Integrity: Theory and Experiment, Edited by E. S. Folias, Kluwer Academic Publishers, The Netherlands, 1989.
• Ibid., presented at the 24th Annual Meeting of the Society of Engineering Science, University of Utah, September 1987.

Additional Publications

Authored several technical reports in the period 1987 to 1993 detailing original research work performed at Hercules Aerospace Company as an individual contributor. Due to its Classified and Company Proprietary nature, this work has been peer reviewed and published with a limited distribution that includes only Department of Defense, NASA, and Hercules personnel. A summary of this work follows.

• F. E. Penado (1993). "Space Structures Improved Joint Design and Analysis: Failure Prediction," Progress Report, IRAD No. 93504-3, March 1993.
  Progress work in the development and verification of failure criteria to predict crack initiation and propagation in bonded joints with composite adherends.


• F. E. Penado (1992). "Space Structures Improved Joint Design and Analysis: Analysis of Singularities Part II," Hercules Interim Report IRAD/2343/1-0010, July 1992. Final Report IRAD/2343/1-0011, February 1993.
  Derived special numerical analysis procedures to implement the global/local model derived in 1991. Programmed this method into a post-processor that can be used with any available finite element code and requires no modification of the FE code.


• F. E. Penado (1991). "Space Structures Improved Joint Design and Analysis: Analysis of Singularities Part I," Hercules Interim Report IRAD/7260/1-0010, August 1991. Final Report IRAD/7260/1-0011, January 1992. Also 1991-92 Hercules Missiles, Ordnance and Space IR&D Technical Report RI-91504 to Department of Defense and NASA.
  Derived a global/local numerical procedure based on eigenfunction expansions and finite elements to calculate stresses, displacements and stress intensity factors near singularities at bimaterial anisotropic interfaces. This method can be applied to very complex structures.


• F. E. Penado (1990). "Space Structures Improved Joint Design and Analysis: End Fitting Optimization," 1990 Hercules Missiles, Ordnance and Space IR&D Technical Report RI-90504 to Department of Defense and NASA.
  Designed, analyzed, optimized and verified through a testing program an all-composite spacecraft joint end-fitting that is 20% stronger and 35% lighter that state-of-the-art fittings made of Titanium.


• F. E. Penado (1989). "Space Structures Improved Joint Design and Analysis: Fracture Characterization," Hercules Interim Reports IRAD/7260/1-001 through 1-003, May, August and November 1989. Final Report IRAD/7260/1-004, April 1990. Also 1989 Hercules Missiles, Ordnance and Space IR&D Technical Report RI-89504 to Department of Defense and NASA.
  Developed experimental techniques and analysis methods for the mixed-mode fracture characterization of adhesives.


• F. E. Penado (1988). "3D Analysis of a Bolted Joint for the NASA Space Shuttle Solid Rocket Motor Case Segment," Hercules Internal Report HITC/T214/240-3000, August 1988.
  Derived a method for the 3D finite element analysis of contact problems. Applied the method to the Hercules design of a bolted joint for the Space Shuttle rocket motor case segments to assess seal gap motion and structural integrity under assembly and flight loads.


• F. E. Penado (1988). "Fiber Optic Damage Detection in Composite Structures," Hercules Progress Report, May 1988.
  Developed analytical techniques to evaluate the effect of embedded optical fibers in composite structures.


• F. E. Penado (1988). "Design and analysis of Composite Bolted Joints," Hercules Internal Report HITC/T214/240-2183, March 1988.
  Developed analytical techniques to predict the strength and mode of failure of bolted joints with composite laminates. Applied these techniques to the redesign of the aft joint of the SRAM II rocket motor.


• F. E. Penado (1988). "Interactive Design and Analysis of Composite Structures: Damage Tolerant Structures," Hercules Interim Report HITC/T214/240-2000, November 1987. Final Report HITC/T214/240-2070, January 1988. Also 1987 Hercules Missiles, Ordnance and Space IR&D Technical Report RI-87B10202 to Department of Defense and NASA.
  Developed a procedure based on finite elements and fracture mechanics to predict the damage region due to low velocity impact in tubular composite structures.

Other Research Activities

As the Composite Space Structures IR&D Group Leader at Hercules Aerospace Company, supervised the research work of several Principal Investigators. Responsible for technical guidance, work plans, progress, budget, deadlines, reports, and presentations to government organizations. The details of this work are documented in internal and government reports. A summary of the accomplishments attained by the group in the period 1989 to 1993 follows.

• Hercules Space Structures IR&D, Weight Optimized Tubes. Work period: January 1989 to March 1993.
  Optimized the weight-to-strength ratio of structural composite tubes by developing an advanced design that eliminates the buckling mode of failure. Verification testing confirmed the analytical prediction of 14% weight savings for the same strength as state-of-the-art composite tubes used in space trusses.


• Hercules Space Structures IR&D, Heat Dissipation Panels. Work period: January 1990 to December 1992.
  Developed a new optimized design for satellite heat dissipation panels that takes advantage of the high axial thermal conductivity of unidirectional composites and compensates for their low transverse and through-the-thickness conductivities. The overall result is an advanced panel that exceeds the currently used aluminum in heat dissipation capabilities but is 30% lighter.


• Hercules Space Structures IR&D, Antenna Radiating Elements. Work period: January 1990 to December 1991.
  Designed, analyzed and manufactured two types of antenna feed horns, quadridged and corrugated, that are over 90% composite and are, respectively, 83% and 40% lighter than state-of-the-art metal horns. Electronic testing demonstrated that the composite horns met or exceeded all specifications of the metal horns, including energy reflection, radio frequency isolation and relative gain.


• Hercules Space Structures IR&D, Space Resins. Work period: January 1989 to March 1993.
  Developed a new thermoset resin that absorbs very little moisture (<0.03% by weight, or over forty times less than current resins) and is resistant to atomic oxygen erosion in low earth orbit. This resin advances the state-of-the-art in the manufacture of dimensionally stable composite space structures such as optical benches and tracking and pointing systems, where moisture absorption prior to launch and desorption in space could be concerns.


• Hercules Space Structures IR&D, Parabolic Sandwich Dishes. Work period: January 1992 to December 1992.
  Developed a low cost manufacturing process to build composite parabolic sandwich reflector dishes with tight dimensional tolerances and high stiffness. A full-size part was built using this one-step process that demonstrated the ability to meet the target cost, weight, stiffness, thermal expansion and dimensional constraints.


• Hercules Space Structures IR&D, Composite Mirrors. Work period: January 1989 to December 1990.
  Developed a new low cost manufacturing process to produce composite mirrors having reflective surfaces shown to be suitable for solar concentrator applications. An optional step in this process involving a planarizing coating can be used to further improve surface finish and impart resistance to atomic oxygen erosion in low earth orbit.


• Hercules Space Structures IR&D, Cryogenic Tanks. Work period: January 1989 to December 1989.
  Achieved unlined composite cryogenic tanks, for the storage of liquid hydrogen and oxygen fuels, that demonstrated no permeation or microcracking under thermal cycling and thermal shock.


• Hercules Space Structures IR&D, Ultra-thin Prepregs. Work period: January 1990 to December 1991.
  Developed a high quality ultra-thin prepreg made of high stiffness PAN fiber and less than 0.001 in. thick, or two and a half times thinner than previously achievable prepregs with this kind of fiber and resin system. Testing of specimens made with this prepreg to verify quality indicated the same mechanical properties as thicker prepregs.


• Hercules Space Structures IR&D, Resin Transfer Molding. Work period: January 1990 to December 1990.
  Extended the resin transfer molding process to allow the manufacture of parts of very complex geometry. Innovative concepts for inner and outer molds were introduced and demonstration parts manufactured. Testing of these parts verified their relatively high strength and uniformity of wall thickness.


• Hercules Space Structures IR&D, Dimensionally Stable Shells. Work period: January 1989 to December 1989.
  Developed a manufacturing process for dimensionally stable thin shells for monocoque parabolic reflectors. The process was demonstrated by manufacturing segments for a 10-ft. diameter reflector having a thickness of 0.008 in., a surface profile < 0.002 in. RMS and a surface finish < 8 microns.


• Hercules Space Structures IR&D, New Co-curing Process. Work period: January 1991 to December 1992.
  Developed a new co-curing technique for sandwich composite panels with aluminum honeycomb core. This new process produced panels with negligible dimpling, less than 0.5% voids and 30% lower manufacturing costs