B. Burks

Failure prediction analysis of an ACCC conductor subjected to thermal and mechanical stresses

In this work, the Aluminum Conductor Composite Core¿ (ACCC) was numerically investigated to evaluate stress distributions when subjected to thermal and mechanical loads. The thermal analysis was conducted to simulate the cooling cycle of the rod from 250°C to room temperature. Three types of mechanical loads were considered, namely axial tension, small bending, and large bending conditions. This was done to predict potential mechanical failure modes, which could reduce the short term performance of the conductors. It has been shown that the magnitudes of the residual thermal stresses in the composite core are low and insufficient to create internal mechanical damage during manufacturing. As expected, the axial tension analysis indicated that under extreme axial tensile loads the ACCC rod will fail catastrophically. The most important results were obtained through the bending analysis, especially under large displacement conditions. Under these conditions the ACCC rod will develop mechanical compressive damage in its carbon fiber/epoxy section if the rods are bent around relatively small mandrels either during transportation or installation.

A modal acoustic emission signal classification scheme derived from finite element simulation

The ability of broadband modal acoustic emission to classify the most common forms of damage mechanisms occurring within a polymer matrix composite material with rod type geometry has been shown. The composite under study was a unidirectional hybrid polymer matrix composite material, with carbon and glass fibers reinforcing a high temperature epoxy matrix. Signal discrimination was achieved through the development of a classification scheme derived from explicit finite element simulation of the most common deformation mechanisms. The classification scheme identified the type of failure mechanism, as well as the material of origin, based upon the spectral content of the signal which is directly influenced by the wave modes that propagate. The classification scheme was used to evaluate the effect that atmospheric aging at elevated temperature had on the hybrid composite subjected to flexure loading at various time periods. Advantages of the proposed method include computational efficiency, the ability to inherently account for geometric and material boundary layer reflections, as well as the ability to be readily adapted to complex part geometries.