Many weapons components (e.g. firing sets) are encapsulated with blown foams. Foam is a strong lightweight material--good compromise between conflicting needs of structural stability and electronic function. Current foaming processes can lead to unacceptable voids, property variations, cracking, and slipped schedules which is a long-standing issue. Predicting the process is not currently possible because the material is polymerizing and multiphase with changing microstructure. The goals of this project is: (1) Produce uniform encapsulant consistently and improve processability; (2) Eliminate metering issues/voids; (3) Lower residual stresses, exotherm to protect electronics; and (4) Maintain desired properties--lightweight, strong, no delamination/cracking, and ease of removal. The summary of achievements in the first year are: (1) Developed patentable chemical foaming chemistry - TA; (2) Developed persistent non-curing foam for systematic evaluation of fundamental physics of foams--Initial testing of non-curing foam shows that surfactants very important; (3) Identified foam stability strategy using a stacked reaction scheme; (4) Developed foam rheology methodologies and shear apparatuses--Began testing candidates for shear stability; (5) Began development of computational model; and (6) Development of methodology and collection of property measurements/boundary conditions for input to computational model.
Monitoring the condition of critical structures is vital for not only assuring occupant safety and security during naturally occurring and malevolent events, but also to determine the fatigue rate under normal aging conditions and to allow for efficient upgrades. This project evaluated the feasibility of applying integrated, remotely monitored micro-sensor systems to assess the structural performance of critical infrastructure. These measurement systems will provide forensic data on structural integrity, health, response, and overall structural performance in load environments such as aging, earthquake, severe wind, and blast attacks. We have investigated the development of ''self-powered'' sensor tags that can be used to monitor the state-of-health of a structure and can be embedded in that structure without compromising the integrity of the structure. A sensor system that is powered by converting structural stresses into electrical power via piezoelectric transducers has been demonstrated including work toward integration of that sensor with a novel radio frequency (RF) tagging technology as a means of remotely reading the data from the sensor.