Tensile mechanical properties and constitutive model for HTPB propellant at low temperature and high strain rate

Abstract

To investigate the mechanical properties and fracture mechanisms of hydroxyl-terminated polybutadiene (HTPB) propellant at low temperature and high strain rate, uniaxial tensile tests were conducted over the range of temperatures 233 to 298 K and strain rates 0.4 to 14.14 s 21 using an INSTRON testing machine, and scanning electron microscope (SEM) was employed to observe the tensile fracture surfaces. The experimental results indicate that the deformation properties of HTPB propellant are remarkably influenced by temperature and strain rate. The characteristics of stress-strain curves at low temperatures are different from that at room temperature, and the effects of temperature and strain rate on the mechanical properties are closely related to the changes of properties and the fracture mechanisms of HTPB propellant. The dominating fracture mechanism depends much on the temperature and changes from the dewetting and matrix tearing at room temperature to the particle brittle fracture at low temperature, and the effect of strain rate only alters the mechanism in a quantitative manner. Finally, a nonlinear viscoelastic constitutive model incorporating the damage evolution and the effects of temperature and strain rate was developed to describe the stress responses of this propellant under the test conditions. During this process, the Schapery-type constitutive theories were applied and one damage variable was considered to establish the damage evolution function. The overlap between experimental results and predicted results are generally good, which confirms that the developed constitutive model is valid, however, further researches should be done due to some drawbacks in describing the deformation behaviors at very large strain.

Experimental Investigation on High Strain Rate Tensile Behaviors of HTPB Propellant at Low Temperatures

“….T he effects of temperature and strain rate on s m and E are consistent with that we got in previous work [11].H owever,t he mechanical parameters' values in this study are all obviously highert han that at the same strain arte and low temperature in our previous work.…”

“…At the lowest temperature and highest strain rate, the stress quickly reaches its maximum value at small strain and then drops rapidly.T he above characteristics of stress-strain curves are different from that of our previous work [11].T he main difference is that the strain softening region was not found in the presents tress-strain curvea tl owert emperatures( < 253 K) and higher strain rates (4-14.29 s…”

“…Based on the above discussions, the strain rate can changet he fracture mechanism of HTPB propellant at room temperature, which is different from that of our previous work [11].T he strain rate for the transition from dewetting and matrix tearing to AP particle fracture is at 14.29-42.86 s…”

“…Solid propellant based on hydroxyl-terminated polybutadiene (HTPB) binderh as become the workhorse propellant in present-day SRM worldwide [10].I ts high strain ratet ensile behaviors have beens uccessfully studied in our previous work basedo nt he tests at strain rates lowert han 14.14 s À1 [11].H owever,t he effects of strain rate and temperature on the tensile mechanical properties and fracture mechanisms of the propellant at higher strain rates are still unclear.M eanwhile, the effects of other influencingf actors )a nd temperatures (233-298 K) using an INSTRONt estingm achine. Scanning electron microscopy (SEM) was employedt oo bserve the tensile fracture surfaces.…”

Effects of Low Temperature and High Strain Rate on the Tensile Behaviors of High-Performance Energetic Composite

“…However, up to now, to the best of our knowledge, there are few analyses on the high strain rate (1-10 2 s -1 ) behaviors of solid propellants at low temperatures. In our previous work [9][10], a new test method had been proposed to study the tensile behaviors of HTPB propellant at those loading conditions. Furthermore, the mechanical properties, failure mechanisms and constitutive model of the propellant had been also investigated based on the test results.…”