Date of Award

8-2012

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Roberto Lopez-Anido

Second Committee Member

William Davids

Third Committee Member

Eric Landis

Abstract

Over recent years graduate researchers at the University of Maine's Advanced Structures and Composites Center, with funding from the US Army Corps of Engineers Research and Development Center (ERDC) have been developing modular structures for blast force protection. Through this research program a rapidly deployable high performance flexible wall system, panelized into 4' x 8' sections was developed. This system passed the Army Unified Facilities Criteria (UFC 4-010-01) for expeditionary and temporary structures. This work focuses on developing a more cost efficient blast protection system, as well as developing structural mechanics methods for panel modeling to more accurately predict blast performance. The objective of the research is to characterize the improved structural framing members in a second generation (2G) flexible wall panel design, and develop a model capable of predicting the load-displacement blast response for a variety of pressure and impulse (PI) combinations. This research initially used quasi-static lab- based material testing to compare the peak strength and energy absorption capacity of potential composite reinforced materials for the 2G design to the first generation (1G) CHARACTERIZATION AND IMPROVEMENT OF WOOD-BASED THERMOPLASTIC REINFORCED FLEXIBLE WALL PANELS design of the flexible wall panels. Using the top performing materials, the 2G wall panels were constructed and directly compared to 1G wall panels in a series of dynamic tests using a Blast Load Simulator (BLS). Using the BLS, air blast tests were used to compare the enhanced 2G design of the blast resistant structure to the existing 1G design. Following the air blast testing, slight adjustments were made to the 2G design and a full-scale building was constructed and tested under full-scale live explosive testing. Results showed that the enhanced 2G system exhibited a desirable failure mode, with adequate energy absorption during blast events, and contained splintering better than the existing 1G design. These live blast tests at various threat levels demonstrated the capability of the system; however, it also revealed a weakness: a lower fastener capacity between the composite studs and sheathing. Lab tests of the fasteners quantified the withdrawal and lateral capacity of the fasteners in the existing and enhanced panel framing components, and methods of further improving the fastener performance were investigated. In addition to the standard ASTM test methods, alternative experimental methods were developed to mimic fastener loading during panel loading. A modified nail withdrawal apparatus was developed to load a line of six fasteners at once, and a second apparatus was developed to load fasteners perpendicular to the edge grain of the reinforced materials. Load displacement histories to complete nail withdrawal were recorded for later use in panel modeling. Pressure-time histories recorded during the simulated air blast testing as well as the lab-based material and fastener testing were used to develop a 3D finite-element model of the flexible wall panel system. The model-predicted and lab-measured results of the panel displacement versus time histories were compared. Results showed an accurate prediction of peak displacement for relatively even pressure and impulse (PI) combinations whereas the unbalanced extreme PI combinations deviated from the measured response.

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