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The evolution of the lateral contraction ratio of two commercial (high and low temperature cure) epoxy resins is studied in uniaxial tension using moire' interferometry. The ratio of transverse to axial strains evolves from an elastic value of about 0.40 to a rubbery plateau value of 0.49 at long times. Furthermore, the data indicate that the contraction ratio follows time-temperature superposition with a shift function indistinguishable from other axial viscoelastic functions. The lateral contraction behavior at several cure states past gelation was measured and a model is proposed to describe the cure dependence., Published in the Journal of Experimental Mechanics, v47 p237-249, 2007.

Proper design of lightweight laminated composite armor relies on the engineer's ability to specify the acoustic impedance of each layer. In conventional, opaque laminated armor systems, stress waves can be efficiently transmitted throughout the structure with a gradual variation of the acoustic impedance from one layer to the next. In transparent systems, however, the engineer can only choose between monolithic glass, ceramic, or polymer systems, resulting in a large acoustic impedance jump between polymer and ceramic layers. In this work we manufacture a novel transparent polymer-glass composite to be used as an intermediate impedance material. This transparent nanocomposite is created by infiltrating nanoporous glass (Vycor, Corning Inc.) with different polymers. The Vycor pores (4-6 nm) are much smaller than the wavelength of light, thus refractive index matching with the polymer is not necessary for transparency., See also ADM002075., The original document contains color images.

Embedded communication busses are being widely investigated for complex composite structures such as military vehicles and advanced civil structures. The major difficulty with such busses is coupling external devices to embedded optical and electrical cables at ingress/egress points because physical connectors are awkward and prone to mechanical failure. In this work we present several techniques for normal incidence free-space optical data porting. These techniques are used to develop and demonstrate an integrated structural optical communication bus., See also ADM002075. Presented at the Army Science Conference (25th) held in Orlando, FL, on 27-30 Nov 2006. Prepared in collaboration with Army Research Laboratory, Aberdeen, MD, and Winona State University, Winona, MN. The original document contains color images.