Hasan Çallıoğlu

ELASTIC–PLASTIC STRESS ANALYSIS OF LAMINATED COMPOSITE BEAMS UNDER LINEAR TEMPERATURE DISTRIBUTION

This study deals with elastic–plastic stress analysis of symmetric laminated composite beams with perfectly clamped ends under linear temperature distribution. The Bernoulli–Euler theory is used during the solution considering infinitesimal small deformations. The composite beam is assumed to be linear strain hardening. The Tsai–Hill theory is used as a yield criterion in the solution. The stacking sequences of the composite beam are chosen as (90°/0°)s, (30°/−30°)s, (45°/−45°)s, (60°/−60°)s and also (0°)4 and (90°)4 in comparison with the composite beam of a single layer in the literature. The results obtained are in good agreement with the literature. The temperature that causes plastic yielding is found to be highest for the (30°/−30°)s stacking sequence, in order to compare with the others, except for the (0°)4 orientation. Residual thermal stresses are particularly important because they can increase the strength of the composite or may lead to premature failure. The residual stress components (σ x ) r are found to be highest at the upper and lower surfaces. When the plastic region expands further with increased temperature, the residual stress components become highest at the elastic–plastic interface.

Vibration Analysis of Multiple Delaminated Composite Beams

Abstract In this study, the effects of location, size and number of delaminations, boundary conditions, orientation angles and stacking sequences on the natural frequency of laminated composite beams are investigated experimentally, analytically and numerically. Two-dimensional finite element models of the delaminated beams are obtained using ANSYS (Finite ElementMethod Code). The analytical method is developed using Euler–Bernoulli beam theory. Then, analytical results are compared with the results available in the literature and the numerical and experimental results in the present study. It has been seen that all results obtained are very close to each other. It is shown that the natural frequencies decrease when sizes and numbers of edge and middle delaminations in the beam increase, and the location of the delamination is also very important.The first natural frequency value of beam of [0°/90°]8 is found to be the highest as compared to the beamswith angles [30°]16 and [60°]16. However, the natural frequency values in the beams that have the angle-ply of [θ]16 are lower than those of [θ/−θ]8, [(θ/−θ)4]s and [(θ/−θ)s]4.