SPECTRAL STRIP ANALYSIS FOR COMPOSITE CYLINDERS SUBJECTED TO LATERAL IMPACT

An efficient computational method, combining the spectral element and the finite-strip method (spectral-strip) is developed in order to obta in numerical results to time dependent problems of cylindrical composi te structures subjected to lateral impact, within moderate CPU times. The finite strip method is applied to cylindrical structures uses glob al interpolation in the circumferential direction, and spectral elemen ts in the meridional cross section. A term superposition solution is o btained, where every iteration refines the solution and is independent of former iterations. In this manner, a full three-dimensional soluti on to the problem of the dynamic response of cross-ply cylindrical com posite shells subjected to a lateral impact, is obtained. The stabilit y and the accuracy of the method are examined. The main goal is to pre dict the damage caused by a high velocity non penetrating impact of mi croparticles. Two types of shells are studied - thin and thick cross-p ly laminates. The effect of curvature on a high velocity impact is stu died. Also, the stress field obtained by the finite element code is in vestigated and damage evaluation is discussed. The present work focuse s on moderate and high velocity impacts and therefore the force durati on is of the order of the through-the-thickness propagation time, caus ing the impact region to be in tension due to the reflected stress wav e. The results demonstrate the dilatational compression wave traverses the shell thickness as a result of the impact and the dilatational te nsion wave reflected from the interior free surface as well as the pro pagation of shear waves in different directions. Using failure criteri a, one can find that the compressive stress wave causes matrix crackin g and the tensile stress wave causes both delamination and matrix crac king. It is shown that for a thin cylinder, the impact phenomenon is c oncentrated near the striking region while for a thick-walled cylinder the results of the impact are visible in points far from the striking point as well. The interference of the stress waves that circumvent t he cylinder create other points of local maxima for the equivalent str esses. The code written for the finite element solution employs the ob ject oriented programming through the C + + language. A special matrix class is developed to perform various linear algebra operations.