Quasi-Isotropic, Thick Composite Laminates Fabricated by the Matched Metal Die Compression Molding Process

Abstract

One of the designs currently being explored under the DOE/LLL composite flywheel rotor development effort is the tapered thickness laminated disk “Stodola” rotor concept. The goal of this effort is to develop a prototype high-energy-density, economical composite laminate rotor for utilization in hybrid flywheel/electric/ICE vehicles and in stationary applications. In terms of energy density, the objective is to obtain 88 Wh/kg at failure with an operational range of 44–55 Wh/kg and an energy storage capacity of approximately 1 kWh. To that end, a high-strength graphite/epoxy (Celion 6000/5213) (0/±45/90) composite laminate tapered disk was fabricated and spin tested. Table 1 presents the test results. It appears from Table 1 that the governing failure criterion is the off-axis failure strength, which is typically lower than the strength along the fiber direction in most quasi-isotropic laminates. This strength anisotropy results in the under-utilization of the laminate strength and in lower energy densities. This suggests that there are two avenues open to improve the performance of laminated disk rotors: (1) increase the basic strength of the composite, and (2) reduce the strength anisotropy of the laminate.