Characteristics of pre-strained polyisocyanurate foam: Deformation recovery and compressive mechanical behavior at cryogenic temperature

In this study, mechanical characteristics of pre-strained polyisocyanurate foam were investigated based on the uniaxial compression test. The compression test procedure was divided into two steps: pre-straining and the typical compression test for the recovered specimen. To evaluate the effect of pre-straining, four different compressive strains were considered, and the temperature and the strain rate dependencies on its mechanical characteristics were analyzed. Test results showed that the recovery ratio decreased substantially for 0.85 (ambient temperature) and 0.25 (cryogenic temperature), and polyisocyanurate foam pre-strained at cryogenic temperature revealed an earlier start of densification. Based on the deformation mechanism of the polymeric foam, the collapse of cells in the pre-strained polyisocyanurate foam was addressed to explain the distinguished features in compressive mechanical characteristics regarding test conditions.

Modeling of shape-memory alloys in scramjet engine applications

This work consists of a theoretical-analytical modeling using applications of intelligent materials, called shape-memory alloy (SMA), in scramjet engines varying the speed from Mach 7 to 14. Through the shockwave relationships, the angles, the Mach number and the recoil distance at the leading edge of the cowl were found out, to select the SMA that has the best deformation recovery. After using the theoretical Auricchio model, the superelastic behavior of the alloys was observed for different elastic properties in the austenite and martensite phases to perform a computational simulation, using the finite element method in Solver ANSYS, in order to represent the performance of the material in a simpler way.