Every day, millions of users interact in real-time via avatars in online environments, such as massively-multiplayer online role-playing games (MMORPGs). These online environments could potentially be unique research platforms for the social sciences and clinical therapy, but it is crucial to first establish that social behavior and norms in virtual environments are comparable to those in the physical world. In an observational study of Second Life, a virtual community, we collected data from avatars in order to explore whether social norms of gender, interpersonal distance (IPD), and eye gaze transfer into virtual environments even though the modality of movement is entirely different (i.e., via keyboard and mouse as opposed to eyes and legs). Our results showed that established findings of IPD and eye gaze transfer into virtual environments: (1) male-male dyads have larger IPDs than female-female dyads, (2) male-male dyads maintain less eye contact than female-female dyads, and (3) decreases in IPD are compensated with gaze avoidance as predicted by the Equilibrium Theory. We discuss implications for users of online games as well as for social scientists who seek to conduct research in virtual environments.

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In this work, the features of the fracture surfaces of graphite-epoxy specimens as seen by both optical and scann ing electronic microscope (SEM) are presented. A variety of test conditions were investigated. They are: tension (quasi- static), compression (quasi-static), and tension-tension fatigue. Failure due to delamination was also studied (Mode I-Peel Testing). The sequence of events leading to failure was monitored using an X-ray technique with an opaque additive for image enhancement. After mechanical testing, specimens were sectioned and prepared for microscopic analysis. Two principal fracture surface features were identified: (1) overlapping platelets of epoxy and (2) branched microcrack structures. These fatures could be used to identify the direc tion of failure propagation and, in some cases, distinguish between failure modes.

An ultrasonic resonance technique for compressional and shear waves velocity measurements in thin composite laminates is described. The method utilizes a computer digitizing scheme and Fourier transform from time to frequency domain. Results showed an eight percent difference in compressional wave velocity across plies for specimens of two different fiber/resin systems. No difference was observed for specimens having different ply-orientations within a system. Shear wave velocity in one specimen was found to be 46% of the compressional wave velocity. The new technique could also be used for thickness measurements in thin-skin honeycomb structures.

A modified X-ray nondestructive testing technique was used to study matrix cracks parallel to fibers and delaminations between plies in graphite-epoxy composite material. A tetrabromoethane (TBE) opaque additive applied at the source of the damage zones enhanced the flaw image. Center-slit specimens were fabricated from Modmor II/Narmco 5208 graphite-epoxy laminates with three different ply orientations. Tensile ramp and sawtooth cyclic loadings at different levels were applied to these specimens. Periodic X-ray monitoring was conducted to observe the initiation and growth of cracks and delaminations at the slit tips. The initiation of damage zones appeared as fiber separation in the ±45-deg directions tangent to the semicircular periphery of the cutout tips. As the load level was increased, this fiber separation continued while fiber separation at other locations also appeared. Delamination first occurred at approximately the same time as fiber separation. The delaminated area was found to surround the most severe fiber separation region and grew in size as the load level was increased. Limited test results indicated a slow and an accelerated damage growth rate during ramp loading. For cyclic loading the majority of growth occurred on the first load cycle. Subsequent cyclic loading to the same level contributed little additional growth in the majority cases.