Accurate prediction of A-basis and B-basis strength levels is critical for risk reduction in design of advanced composite aircraft structures. Calculation of polymer matrix composite allowables for aerospace applications is governed by FAA and MIL-HDBK-17E standards. The process is costly and time consuming as large numbers of coupon tests are inevitable.
This presentation primarily focuses on:

• FAA categories of damage tracking for composite structures under service.
• Estimation of mechanical and fracture properties of composites.
• Generation of A basis and B-basis allowable properties that are statistical in nature.

In order to reduce costs and product lead-time, Virtual Testing (VT) can be used to reduce the scale of physical testing necessary for calculation of A-B base allowables. Virtual Testing involves an accurate simulation of physical tests using multi-scale Progressive Failure Analysis. Data will be shown that compares coupon test results with VT predicted strengths for several different laminates. The scatter in physical tests is treated with Probabilistic Progressive Failure Analysis. The multi-scale analysis is based on a hierarchical analysis, where a combination of micro-mechanics and macro-mechanics is used to analyze materials and structures in great detail. Additional data will show the layer-by-layer analysis employed to determine the residual strength of a curved honeycomb fuselage panel undergoing longitudinal loading.

VT relies on physics-based failure criteria to reduce its dependence on empirical-based procedures. This is more than a simple mix of analysis and test because: (1) the root cause of failure at the micro-scale is modeled, (2) VT is incorporated into each stage of the FAA building-block process, and (3) material and manufacturing data scatter is accounted for. The methodology is applicable to notched and un-notched coupons and structures and has the potential of reducing the test coupon count by over 60%. The computational approach will be discussed and its application on various examples of fuselage certification will be given.

Dr. Frank Abdi is the founder of Alpha STAR Corporation and brings this project an extensive knowledge of the various DOD, NASA and Industry software packages providing detailed evaluation and technical guidance for the methods being proposed for analysis of low/high temperature composite structures. Dr. Abdi has a strong theoretical and experimental background in structural materials technology including the derivation and modification of: Theoretical equations, aero-elastic tailoring (composite tapering), optimization, material design, fatigue, creep, fracture mechanics, structural mechanics, analysis of structures, and use of computers to implement these techniques.

Dr. Abdi worked at Rockwell International for fifteen years where he was the manager of Advanced Program’s Controlled Configured Vehicle Research organization. Dr. Abdi has over thirty years experience in computer based modeling and code development for a range of applications associated with advanced structures, material processing and composite mechanics with a unique background in finite difference and finite element as applied to aerospace components in support of Rockwell's division. While at Rockwell he was responsible for design and simulation of: NASP (X30), B1-B bird strike, Advanced Launch System (ALS), Boosted Penetrator, Swedish Fighter, Special Operation Aircraft (SOA), and shuttle redesign.

Within Alpha STAR he has been responsible for: Advanced Composite Technology durability and damage tolerance program, Aero-elastic concept engineering (ACE) and several NASA sponsored SBIR, STTR, and ATP and computational structural mechanics (CSM) projects. He has the affiliation with the following professional organizations: American Society of Mechanical Engineers, AIAA (member of Optimiza¬tion Committee), AIAA (member of Adaptive Structure Committee), NASA Ames (Committee in Aircraft Conceptual Design), and SAE (member of RMS Committee). He has published over 40 journal papers in optimization, materials science and computational structur¬al analysis, authored a book in process optimization and edited another book. Dr. Abdi received a B.S. and a M.S. in Mechanical Engineering from University of Michigan in 1974 and 1975 respectively, and a Ph.D. in Mechanical Engineering from University of Southern California in 1979.