Ultrasonic Velocity in the Liquid‐Glass Transition Region

1958 ◽  
Vol 30 (9) ◽  
pp. 856-859 ◽  
Author(s):  
T. A. Litovitz ◽  
T. Lyon
Keyword(s):  
Glass Transition ◽  
Transition Region ◽  
Ultrasonic Velocity ◽  
Liquid Glass ◽  
Glass Transition Region

scholarly journals Buckling and vibration analysis of shape memory laminated composite beams under axially heterogeneous in-plane loads in the glass transition temperature region

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Nilesh Tiwari ◽  
A. A. Shaikh
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Boundary Conditions ◽  
Shape Memory ◽  
Transition Region ◽  
Shape Memory Polymer ◽  
Shear Deformation Theory ◽  
Effect Of Temperature ◽  
Glass Transition Region

AbstractBuckling and vibration study of the shape memory polymer composites (SMPC) across the glass transition temperature under heterogeneous loading conditions are presented. Finite element analysis based on C° continuity equation through the higher order shear deformation theory (HSDT) is employed considering non linear Von Karman approach to estimate critical buckling and vibration for the temperature span from 273 to 373 K. Extensive numerical investigations are presented to understand the effect of temperature, boundary conditions, aspect ratio, fiber orientations, laminate stacking and modes of phenomenon on the buckling and vibration behavior of SMPC beam along with the validation and convergence study. Effect of thermal conditions, particularly in the glass transition region of the shape memory polymer, is considerable and presents cohesive relation between dynamic modulus properties with magnitude of critical buckling and vibration. Moreover, it has also been inferred that type of axial loading condition along with the corresponding boundary conditions significantly affect the buckling and vibration load across the glass transition region.

Thermal Analysis of Nomex® and Kevlar® Fibers

1977 ◽  
Vol 47 (1) ◽  
pp. 62-66 ◽  
Author(s):  
J. R. Brown ◽  
B. C. Ennis
Keyword(s):  
Thermal Analysis ◽  
Thermal Decomposition ◽  
Glass Transition ◽  
Melting Point ◽  
Transition Region ◽  
High Temperatures ◽  
High Performance ◽  
Polymer Melt ◽  
Glass Transition Region ◽  
Dta Curves

DTA, TG, and TMA curves of commercial Kevlar® 49 and Nomex® fibers have been used to assess their behavior at high temperatures. The fibers lost absorbed water around 100°C, and a glass transition was reflected in the DTA and TMA curves in the region of 300°C. Difficulties in the interpretation of DTA and TMA curves in the glass-transition region and in the assignments of Tv‘s for these high-performance fibers are discussed. Whereas Kevlar 49 showed both a crystalline melting point (560°C) and a sharp endothermal thermal decomposition (590°C), Nomex showed only the latter (440°C) and no evidence of melting from the DTA curves. The endothermal decomposition peaks apparently correspond to “polymer melt temperatures” reported for related materials, and correlate well with the TG and TMA features. During thermal analysis of Kevlar 49, oxidation occurs more readily than thermal decomposition, but the latter predominates for Nomex. Differences between dyed and undyed Nomex were due to differences in yarn constitution.

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