Issued by Sandia Laboratories, operated for the United States Eneq.Jy Research & Development Admin istration hy Silnrli a Corpo ration. NOTICE This report was prepared as an account of work sponsored by t he United States Government. Ne ither the United States nor th e United States Energy Research & Development Adm10i s• trat io n, nor any of their employ ee s, nor any of th eir co n • tractors. subcontractors, or their emrlny~~'. rnakes any w arranty , expr ess or implied , or assum es any legal liahrlity o r responsibility for th e accuracy, compl eteness or usefulness of an y in for mation, apparatus , product o r r ro cess d isclosed, or represen ts that its use would not infr inge prrvately own ed righ t s. NOTICJ< Reference to a company or prod uct name dnes not imply end o rsement •)r rec orr.men 1ation nf the product by f,a ndia Laboratorie~ ,..,r the 1J. ::. J• n ergy Research and Developr:tent Alu.iiJL~ LraLlon L:) Lh e exclusion 0f other:-thRt ma:r be s ui t able .

Two space applications are considered for (electrically) contactless coilguns: launch of small satellites into low-earth orbit, and launch of lunar liquid oxygen (LLOX) from the moon to the stationary Lagrangian point L2. For the earth-to-orbit (ETO) application, the baseline conceptual design consists of a 960-m long gun sited in a tunnel at 25" inclination. The gun launches a n 1820-kg package that includes a 100-kg satellite and a 650-kg boost rocket for orbital insertion. For the lunar application, the launcher is 200 m long. A 100-kg load of LLOX is packaged in a 10-kg fiber-wrapped tank, accelerated at 2 kgees in an aluminum bucket (armature), and launched at 2.33 km/s at 30-minute intervals. The canisters arrive at L2 2.97 days later and are captured by robotic tugs that deliver them to a fuel depot. The total mass of LLOX delivered per year is 867 Mg (metric tons).

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This paper describes a model for simulating the crushing behavior and predicting the energy absorption characteristics of triaxially braided composite tubes. The crushing model uses the finite element code ABAQUS along with a material module that describes the constitutive behavior of the braid material. The constitutive behavior includes the effects of damage accumulation, and scissoring and jamming of the braider tows. To facilitate the model development, extensive material tests and tube crushing experiments were performed.Crushing tests were conducted on braided carbon fiber/epoxy-vinyl ester composite circular tubes, which were supplied by USCAR's Automotive Composites Consortium. All tests were conducted quasi-statically, and plug-type initiators were used to trigger the progressive crushing. Experimental results show that the profile of the load-displacement curve and the overall energy absorption can be significantly affected by the fiber architecture and the fillet radius of the plug-type initiator being used.In order to verify the proposed model, simulation results for tubes with various braid angles, being crushed with different initiator plugs, are compared with the experimental data. Predictions from the proposed model correlate well with the test results, and provide useful information about the deformation of the tube and the failure mechanisms occurring as the tube is being crushed.

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