Required Capabilities: A test program is required for determining local compressive crippling failure modes and for determining joint actions of very thin structural sections for various material. Of prime interest are: (1) the need for the effects of initial imperfections induced during fabrication and erection processes; (2) the effects of structural property changes due to long exposure to space environment. Data are required for the lightweight metals such as aluminum, titanium, beryllium, etc., and the advanced composites as graphite/epoxy, Kevlar/epoxy, etc. Development Plan: Set up a test program for determining crippling behavior in a space environment of very thin members, of various geometry and materials representative of lightweight orbital structures. The test program should simulate built-in imperfections representative of fabrication and erection anomalies. Set up a test program for determining joint action of typical components for large space structures under tensile, compressive and bending loads. The test would include development of test procedures for testing the joints under simulated space environment. The test programs would include development of test methods for accelerating test behavior for long-life spans under repeated thermal and load cycling. Item — Structural Analytical Tools Criticality — Critical to program success Finite element models of the structural arrangements are needed to evaluate structural behavior. Large space structure must withstand loads associated with stationkeeping and positioning in orbit, orientation, and control. Large space structure must maintain stable geometric configuration during erection and system operations. Investigative and productive behavior of the structure can only be reasonably accomplished through math modeling using the techniques of the finite element approach. Accurate mathematical models, verified by component testing, will ensure that particular design requirements relating to strength, stiffness, control, life, thermal, dynamic response can be satisfied. Present Capability: Requirements for large space structures are a fundamental departure from conventional aerospace structures. The size of the envisioned space structures exceeds the present systems by orders of magnitude. The techniques for constructing the finite element models are available but have not been applied or verified for large space lightweight structures. Required Capabilities: Finite element models are required and need to be developed for the structural analysis and predicted behavior of very large lightweight space structures. The structural response of the structure must be known for all phases of the design project to asure reliability and safety of the structure during erection, system operation, and life of the system. Development Plan; The first step is the development of the substructural finite element model of the basic beam elements. Earth-based testing of components can verify analytical results from which the substructural model can be updated. The second step is to develop a structural model of the larger girder element, made up of structural components. Again earth-based testing,

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