Department of Ocean and Mechanical Engineering

Mode I interlaminar fracture toughness, G IC, of interleaved graphite/epoxy has been investigated with DCB specimens, beam theory, and finite element analysis. Finite element modeling aimed to investigate the influence of interleaf thickness on compliance and energy release rate and possible mixed mode loading in the case of asymmetric interfacial crack. Another objective was to compute crack tip yield zone dimensions as a function of thickness and elastic properties of the interleaf material. The analysis is correlated with experiments. Thermoplastic interleaves enhanced G IC to a great extent. The toughness increased sharply with film thickness to a maximum at 16 mu m and decreased for the thicker interleaves. On the other hand, inadequate adhesion preempted the toughness potential of thermoset interleaves.

This thesis presents a procedure for the selection and design of retaining walls using an expert system. The selection part is formulated in the form of production rules by OPS5, a programming language for production systems, and the design part is written in the procedural language, BASIC. Nine different types of retaining walls are incorporated in the knowledge base of the selection part, and three types of walls in the design part of the expert system. The selection and design parts are combined using OPS5 support routines.

The plume resulting from a subsea well blowout alters the
environmental loading on a floating platform which is
directly above the well. Horizontal ocean currents deflect
the plume and may create a more severe loading on the
structure. During the early stages of a blowout the
"starting plume" induces forces of a different magnitude on
the structure. A preliminary experimental study,
investigating the transient loads induced by starting plumes
and the effects of currents on blowout plumes, was
conducted. The results of the experiments showed that the
forces involve significant fluctuations which are quite
different from the average values. The normal forces induced
by starting plumes were slightly greater. Horizontal
currents caused an increase in the moment acting on the
structure. This is of considerable importance as moments,
when coupled with the situation of flooded decks and
compartments, may cause the structure to sink.