Low Energy Impact Damage Evaluation of Thin Walled Structures

Fibers with high stiffness and strength are now being widely used in the construction of composite cylinders for rocket motor cases and launch tubes to minimize their structural mass. Experimental testing has shown that these composite materials exhibit a real susceptibility to structural damage caused by low energy impact. The resulting impact damage renders the structure unusable, therefore impacting mission readiness and increased costs associated with lost assets. Analytical models which incorporate dynamical analysis, failure analysis, and micromechanical models appropriate for use with composites are required to fully understand impact damage phenomena and determine design enhancements for survivability. An analytical methodology will be developed and validated to predict the development of impact damage. Such a methodology can be used to optimize the design of composite motor cases and launch tubes with significantly improved damage tolerance. This will greatly enhance the capability of the missile system to satisfy the Department of Defense's Insensitive Munition requirements. Immediate benefits from this work will allow for increased reliability, mission readiness and reduced costs, consistent with DOD Operating and Support Cost Reduction (OSCR) initiatives. The methodology to be developed in this Phase I study will include: micromechanical-based material property and failure models for composites with 2D and 3D wound, woven, or braided fiber architectures subjected to low energy (<15 ft-lb) impact conditions. This program will provide a stand-alone analytical tool for designing damage tolerant composite pressure vessels for use in rugged environments. This technology has excellent dual-use potential in the design of insensitive munitions (military) and the design of damage tolerance CNC vehicle fuel tanks (commercial).