The geometrically nonlinear response of sandwich functionally graded cylindrical shells reinforced by orthogonal and/or spiral stiffeners and subjected to axial compressive loads is investigated in this paper. Two types of sandwich functionally graded material models are considered. The formulations are based on the Donnell shell theory considering geometrical nonlinearity and Pasternak’s elastic foundation. The improved Lekhnitskii’s smeared stiffener technique is used to account for the stiffener effects with both mechanical and thermal stresses. The results obtained indicate that the spiral stiffeners have significantly beneficial influences in comparison with orthogonal stiffeners on the nonlinear buckling behavior of shells. The relatively large effects of temperature change, geometrical and material parameters are also demonstrated in the numerical investigations.

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The epoxidized rubber seed oil (EeRSO) was a mixture of epoxidized triglyceride, and epoxidized methyl ester of free fatty acids was used as a secondary plasticizer for PVC. An increase in tensile properties was observed by substituting the 10 phr DOP plasticizer with the EeRSO in PVC formulation. A leaching test was performed in five media to evaluate the plasticizing effect. The sample weight increased slightly after soaking in water and 30 wt.% acetic solution, decreased slightly in 10 wt.% KOH solution, and reduced sharply and strongly in sunflower oil and n-hexane. The 10 phr EeRSO in PVC formulation has presented an improvement in migration, volatilization characteristics, and thermal property of PVC. After 72 hours of soaking in n-hexane, the shore A hardness of the EeRSO plasticized PVC sample increased by 14.5% while the PVC sample without EeRSO was blistered and its shore A hardness could not be measured. This was the clearest evidence for the positive effect of EeRSO as a secondary plasticizer. The morphology of the fractured surface of the samples after immersing in n-hexane was studied by using scanning electron microscopy. Thermogravimetric analysis showed the role of EeRSO in significant improvement in thermal stability. In general, EeRSO not only acts as a primary plasticizer to improve the migration, extraction, and volatilization characteristics but also contributes to the thermal stability of PVC.