Experimental and numerical methods for free vibration analysis of sandwich conical shells with anisogrid composite lattice core

In this study, the modal analysis of sandwich conical shells with a composite lattice core was presented using experimental and numerical methods. For this purpose, samples of such sandwich were made of two identical Kevlar-fabric face sheets and a composite (glass-carbon fibers) lattice core with regular hexagonal cells. Next, modal tests were carried out to extract the natural frequencies and the mode shapes by collecting frequency responses using a laser accelerometer. Also, ABAQUS FE simulations were performed using three-dimensional elements and were validated with the results obtained from modal tests. According to the experimental results, the difference in the natural frequencies of samples is less than 3% for the first mode shape (m,n)=(1,2) and 6% for the second mode shape (m,n)=(1,3). Therefore, it can be concluded that there is the least possible error in the conceptual design and the implementation of various manufacturing processes. In addition, there is good agreement between the results obtained from modal tests and ABAQUS finite element method, i.e. the maximum difference in natural frequencies of the first four mode shape is approximately 16%.