ملخص البحث :

This study represents investigation of the critical buckling load in columns, which consistof two different materials for case of (fixed–free) loading in order to choose the suitablecompound ratio. The investigation is done with two methods: analytical method throughsuggested equation for calculation of equivalent modulus of elasticity and numericalfinite-element method with ANSYS APDL 17.2. The analytical and numerical resultsshowed excellent agreement with each other because of the qualification of the suggested equation of the equivalent modulus of elasticity for the compound column. Thecritical buckling load is sensitive to the difference between the modulus of elasticity forthe two different materials of the compound column, which also affects the ratio of thecritical buckling load to the mass of the compound column.

ملخص البحث :

Free vibration analysis of the isotropic skew plate with three supporting conditions (CCCC, CFCFand FCFC) were studied. ANSYS APDL version 17.2. with two-dimensional model (SHELL281 element) andthree-dimensional model (SOLID186 element) were adopted. The effects of width-thickness ratio (a/t), aspectratio (a/b), mode number, skew angle and supporting conditions on the first five natural frequencies wereinvestigated. The results showed that the non-dimensional fundamental frequency coefficients (Kf) increaseswhen the skew angle at any aspect ratio (a/b) , mode number and supporting type. Also, the effect of skew angleappears sharply when the skew edges are clamped (i.e. CCCC and CFCF) while in when the skew edge is free ,the effect of skew angle is not appear . Finally, the comparison between the two elements (SHELL281 andSOLID186) shows that there is a good agreement between them when the skew angle is smaller than 60o and themode number is smaller than fourth mode.

ملخص البحث :

This study is presented of two models were built to simulate the skew composite plates and these models are SHELL281 and SOLID186 element. Three types of laminates arrangement were used to study the effect of skew angle, fiber orientation and length-to-width ratio on the first five natural frequencies of the clamped composite plates. The skew angle was changed from (0°) to (75°) with (15°) steps while the fiber orientation was changed from (0°) to (90°) with (15°) steps and the length-to-width ratio was (0.5, 1, 1.25, 1.5 and 2). The results showed that the first five frequency parameters increase for three layouts when the skew angle increases at constant fiber orientation and constant length-to-width ratio. Also, the fiber orientation has a slight effect on the first five frequency parameters in (0/β/0) layout. The effect of length-to-width ratio on the first five frequency parameters depends on the skew angle (smaller or larger than (60o)), fiber orientation and the laminates layout. Finally, the values of the first five frequency parameters of (β/0/β) and (β/β/β) layouts are close to each other.