High velocity impact and penetration of thick composite laminates

Shyan Vittalan Potti, Purdue University

Abstract

Fiber composites are highly heterogeneous. Thick-section composite laminates may contain hundreds of composite laminae. Under impact loading, extremely complex failure modes would occur. The complexity of the state of damage makes an accurate detailed modeling of damage progression almost impossible. To circumvent this difficulty, a new approach was proposed in which a quasi-static punch test was performed on a composite laminate to generate the load-deflection curve during penetration. This punch curve can be considered as the 'structural constitutive model' that captures the highly nonlinear behavior of the laminate in the entire penetration process. The fundamental static punch curve was used in conjunction with a mindlin plate model to model the penetration through the laminate. This approach allows one to use a global model such as the plate model to indirectly account for the very complicated failure process in the laminate. A special two-noded ring element based on the mindlin thick plate theory was formulated to model damage processes during static and dynamic penetration. The model was shown to be capable of predicting the static and dynamic penetration behavior of various target thicknesses and sizes from the information obtained from one static punch test using a small plate. The predicted residual velocities show good agreement with the experimental residual velocities for a range of striking velocities near and above the ballistic penetration limit velocity of the target. Models based on the energy required for penetration of the target under quasi-static conditions and for the energy required for dynamic penetration were also proposed to predict the residual velocities under dynamic impact conditions. These models provide simple and accurate estimates for the residual velocities of the projectile at different incident velocities for the different targets studied. The area of the target that becomes delaminated during impact was shown to increase when the impact velocity was increased until the penetration limit velocity, beyond which the delamination area decreases with an increase in impact velocity. This phenomenon and the area that is delaminated for different size targets at different impact velocities were accurately predicted by the dynamic response model.

Degree

Ph.D.

Advisors

Sun, Purdue University.

Subject Area

Aerospace materials|Mechanical engineering

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