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Head, Ranges, Engineering, and Analysis Department 4D REPORT DOCUMENTATION PAGE Form Approved R DOMB No. 0704-0188Public reporting for this collection of information Is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget Paperwork Reduction Project 10704-0188) Washington, DC 20503.

Lightweight rigid-wall shelters used in mobile military operations are often constructed of sandwich panels comprised of thin face sheets and thick, yet ultra light core materials to minimize weight while maximizing structural integrity. The key structural advantage of sandwich panel construction (SPC) versus homogeneous panel construction (HPC) is the potential for up to an order of magnitude weight reduction while matching equivalent bending stiffnesses. Additional advantages include increases in damping, acoustic and thermal insulation, and possibly ballistic protection performance for a given areal weight density. However, these advantages come at a cost, which often impact the design and manufacturing complexities of critical joints used to connect the sandwich panels in a box-like assembly. Furthermore, stiffnesses of these joints are often difficult to characterize and their finite values significantly influence panel deflections and rotations. While mobile rigid wall shelters must be certified for several transport loading environments including rail impact (vehicle mounted and dismounted), drop shock, mobility and external air transport (EAT), the present effort, addresses survivability against conventional air blast effects. This study employed combined experimental and analytical approaches at the material and sub-structural levels to (1) generate accurate shelter models, (2) validate the material- and sub-structural models and (3) maximize the shelter’s global performance against a conventional air blast event early in the design stage to avoid costly physical tests. The material level tests focused on the mechanics of the assembled constituents that formed the sandwich panel and the benchmarking of an appropriate finite element to predict the displacement, stress and strain responses. The sub-structural level tests focused on loading a structurally representative shelter section to determine the joint behaviors and stiffnesses for model benchmarking purposes. Finally, a complete rigid-wall mobile military shelter model was constructed and its modal behavior was characterized followed by its complete dynamic response to an air blast event.

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information, Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY)2. REPORT TYPE 3. DATES COVERED (From -To) PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) PERFORMING ORGANIZATION University of Texas at Arlington REPORT NUMBEROffice of Sponsored Projects PO Box 19145 Arlington, TX 76019 SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)Office of Naval Research ONR 875 N. Randolph St. One Liberty Center Arlington, VA 22203-1995 NUMBER(S) SPONSOR/MONITOR'S REPORT DISTRIBUTION/AVAILABILITY STATEMENTApproved for Public Release; Distribution is Unlimited. SUPPLEMENTARY NOTES ABSTRACTDuring the period of 7/1/2007 --12/31/2007, we performed the following studies on radar sensor network: 1) Network-enabled Electronic Warfare (NEW) for Collaborative Automatic Target Recognition (CATR); 2) Foliage clutter modeling using narrowband and UWB radars; 3) A propagation Environment Modeling in Foliage using UWB radars; 4) Target detection in foliage using shorttime Fourier transform and UWB radar sensor networks; 5) Some experimental studies on path loss models for wireless sensor networks based on Xbow motes, 6) Theoretical studies on distributed connected dominating set construction in random geometric kDisk graphs for potential application to real sensor networks. SUBJECT TERMSRadar Sensor Network, UWB Radar, Sense through foliage, Automatic Target Recognition, clutter modeling. 1. Network-enabled Electronic Warfare (NEW) for Collaborative Automatic Target Recognition (CATR); 2. Foliage clutter modeling using narrowband and UWB radars; 3. A propagation Environment Modeling in Foliage using UWB radars; 4. Target detection in foliage using short-time Fourier transform and UWB radar sensor networks; 5. Some experimental studies on path loss models for wireless sensor networks based on Xbow motes, 6. Theoretical studies on distributed connected dominating set construction in random geometric k-Disk graphs for potential application to real sensor networks. NEW-CATR: Network-enabled Electronic Warfare for Collaborative Automatic Target RecognitionNetwork-enabled Electronic Warfare (NEW) is to develop modeling and simulation eff...

This research investigated the fracture toughness and crack propagation behaviors of woven fabric reinforced polymer (WFRP) composite laminates subjected to single and mixed mode loadings using numerical models. The objectives were to characterize the fracture behaviors and toughness properties at the fiber/matrix interfaces and to identify mechanisms that can be exploited for increasing delamination resistance. The mode-I and mode-II strain energy release rates GI and GII, the effective critical strain energy release rate, Gc_eff, (also known as the mixed mode fracture toughness) and crack growth stabilities were determined as functions of crimped fiber paths using meso-scale, 2D multi-continuum finite element models. Three variations of a plain-woven fabric architecture were considered; each having different crimped fiber paths. The presence of mixed-mode strain energy release rates at the meso-scale due to the curvilinear fiber paths was shown to influence the interlaminar fracture toughness and was explored for pure single-mode and mixed-mode global loadings. It was concluded that woven fabric composites provided a Fracture Toughness Conversion Mechanism (FTCM) and their toughness properties were dependent upon and varied with positon along the crimped fiber paths. The FTCM was identified as an advanced tailoring mechanism that can be further utilized to improve toughness and damage tolerance thresholds especially when the mode-II fracture toughness GIIc is greater than the mode-I fracture toughness GIc.