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In this paper, the behavior of curved sandwich beam with a soft flexible core, under low-velocity impact, loaded with environmental thermal effects by pursuing the use of the high order shear deformation theory of sandwich structures is investigated. The Sandwich beam is comprised of composite sheets and foam core. The boundary condition is simply supported by probability of circumferential deflection. Two degrees of freedom for mass- spring model was used for modeling the impact phenomena. In the presented formulation, the first order of shearing deformation theory is used for sheets,the core Displacement field is considered unknown and then by using elasticity theory and compatible condition in the core, sheets common face and the relation of stress-strain core deflection are determined. In order to derive the governing equations of beam structure, the Hamilton principle was used. For validation, the results obtained from this research are compared with the results of other researchers and also the numerical result of ABAQUS software. The comparison of results shows good agreement. The effects of various parameters like impact velocity and mass, environmental temperature, core and sheets thickness and materials on core and sheets deflection and core stress and impact force were studied. The obtained results showed that increasing environmental temperature has a slight effect on impact force, but more effect on beam dynamic response. It is also shown that with increasing the hardness of beam, the energy absorption is reduced.

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In this study, the residual strength of the carbon/epoxy composite plates exposed to the thermal cycles and subjected to low-velocity impact was evaluated using an experimental procedure. Composite plates with a layup of [45/0₂/-45/90₂]_s and thickness of 2.9 mm under three impact energy levels of 10J, 15J, and 20J and exposed to 200 thermal cycles in the range of -30 to 65° C went under low-velocity impact and compression after impact tests. In performing impact tests, a drop weight test device was used to investigate the behavior of damaged composites, force-time, force-displacement, and energy-time curves at all test temperatures were analyzed. Finally, the effect of temperature and associated damages at different levels of impact was evaluated using radiographic analysis and optical microscopy. Applying 200 thermal cycles in the temperature range of -30 to 65 ° C caused small cracks in the matrix and reduced the energy absorption of the samples. The highest drop in compressive strength is related to the highest impact energy, 20 J, which has a 31.12% decrease in strength. The thermal cycle at different impact energy levels of 10J, 15J, and 20J has led to an increase in the stiffness and compressive strength of the composite specimens. Finally, material parameters of the semi-empirical Caprino model to estimate the residual compressive strength of the carbon/epoxy plates under low-velocity impact and thermal cycles are obtained.