Changsheng Zhou

Cohesive Zone Modeling of Propellant and Insulation Interface Debonding

The reliability of the bonding of propellant to insulation is a key part of the analysis of rocket motor structural integrity. In this study, the debonding of the propellant/insulation interface was investigated by combining experiment and simulation. The improved exponential cohesive zone model and the bilinear cohesive zone model were used to predict the fracture properties of the adhesive interface. Double cantilever sandwich experiments and uniaxial tensile tests were performed to determine the corresponding model parameters. Furthermore, cohesive parameters were calibrated by applying an inverse analysis based on Hooke-Jeeves optimization algorithm. Good agreement was observed between the numerical simulation of double cantilever sandwich beam tests and the experimental curves. These results demonstrate that cohesive zone models can simulate the crack initiation and propagation of propellant/insulator interface in mode I. The bilinear law was shown to be more suitable for simulating fracture of the propellant/insulation interface in a strict sense than the exponential law. The numerical load-displacement curve was found to be sensitive to all cohesive parameters.

Review of the Adhesively Bonded Interface in a Solid Rocket Motor

One of the most challenging requirements in a solid rocket motor (SRM) is the integrity of the charge structure which is a multilayer adhesive joint involving the propellant, liner, and insulation. The propellant/liner/insulation interface is considered to be the weakest part of the whole structure. This interface has some of the usual features of an adhesively bonded interface, as well as its own special characteristics: the co-cured process, ingredient migration between interfaces, and complicated damage mechanisms. We give a technical and critical review of the past 50 years of existing research on many aspects of the propellant/liner/insulation interface in terms of the adhesive properties and adhesive mechanisms, ingredients migration, damage determination, and fracture analysis. To present a comprehensive outline of this interface we also clarify some remaining problems which should be addressed in the future. With significant improvements in the theoretical and experimental studies of the propellant/liner/insulation interface, the problem of integrity failure of the charge structure in SRM will be well resolved.

Contrastive Research about Fluid-thermal Coupling of Carbon-phenolic Jet Vane in Terms of Two Different Numerical Models

A numerical research on two-dimensional unsteady fluid-thermal coupling of carbon-phenolic jet vane was done through using secondary development by UDF. The main attention is on differences of surface temperature based on two models. The results show that, the highest temperature is always on stagnation point near by the leading edge of jet vane. Temperature of side face will decrease along the main flow direction. In jet vane coordinate system, at the same main flow position, temperature on upwind side is higher than leeward side, and the differences will become greater along the main flow direction. The escaping process of pyrolysis gas and chemical reaction on surface are in favor of reducing surface temperature. And two different numerical models can be used in study of jet vane made of charring materials on different attentions.

Study on the laser irradiation characteristics of NEPE propellant in different oxygen concentrations

The ignition and combustion characteristics of nitrate ester plasticized polyether (NEPE) propellant in different oxygen concentrations ambient gases were studied by the application of CO2 laser, infrared thermometer and high speed camera. The flame intensity data of the propellant was collected by the photodiode; propellant flame temperature was measured by infrared thermometer. The experimental results show that the time which NEPE propellant spend to be stable combustion will get shorter with the increase of oxygen concentration; the flame peak temperature measured by infrared thermometer increases with the increase of oxygen concentration when the oxygen concentration is less than 30% by volume, then decreases with the increase of oxygen concentration.

Extraction of rate-dependent fracture properties of adhesive interface involving large-scale yielding

Interface debonding is one of the major failure modes for the adhesive joints of polymer–matrix composites. The interfacial fracture properties of adhesive interfaces involving large-scale yielding is difficult to determine. A hybrid method that combines modified data reduction and inverse analysis was used to determine the fracture energy of the composite propellant/insulation interface at different loading rates. The modified data reduction adopts effective crack length to account for the effect of the fracture progress zone and avoid monitoring the crack length. These estimated values of the fracture energy were then calibrated by inverse analysis based on the Hooke–Jeeves algorithm in which the interface layer is characterized by a cohesive zone model. The whole process of inverse analysis is conducted automatically without any intervention by procedures. Experimental and numerical results indicate that the proposed data reduction provided fracture energy sufficiently similar to those obtained by the inverse analysis. Moreover, the fracture energy of the propellant/insulation interface was found to rely heavily on the loading rate with a non-monotonic trend.