Numerical Analysis of Laminated, Orthotropic Composite Structures
Contract rept. 1 Jan 1974-31 Dec 1974
ILLINOIS UNIV AT URBANA DEPT OF AERONAUTICAL AND ASTRONAUTICAL ENGINEERING
Pagination or Media Count:
This report presents the two main lines of investigation which were carried out during the past contract year. One investigation was intended to check-out previously developed finite-element computer programs on a large degree-of-freedom composite material model. This was done by applying the analysis to a recoilless rifle configuration. The finite-element grid and the numerical results for this problem are presented and discussed. The second line of investigation was concerned with developing fracture models for composite materials. Two different models were developed. One model deals with interlaminar failure and the other predicts the matrix failure within an individual composite ply. No suitable experimental results are presently available to check out the first model but the second model is found suitable for explaining experimental results dealing with a nonlinear response of certain cylindrical models loaded to failure by internal pressure. These results, obtained from experiments performed at the Ballistic Research Laboratories, show that pronounced nonlinear structural response occurs at a fraction of failure load which suggests that an appreciable degradation of material occurs at relatively low stress levels. It is shown that this phenomenon can be explained by a model that assumes that the shear modulus in the plane of the fibers is reduced by matrix material failure parallel to the fibers.
- Laminates and Composite Materials