The Analysis On Crack Growth Of Solid Propellant

This paper presents the studies on the solid rocket propellant grain innersurface cracks and expansion, as well as grain debonding situation in the effect oftemperature load and internal pressure loads caused by propellant ignition.Currently, HTPB propellants are widly applied in solid rocket motor. HTPBcomposite propellant is a kind of typical viscoelastic materials. The fracture ofHTPB composite propellant will lead to abnormal fuel combustion, increasedpressure within the combustion chamber, the engine is not working properly, oreven sometimes lead to the rocket engine blowing up. Therefore, the mechanicalanalysis of HTPB propellant grain, especially fracture analysis are very important.First, a brief introduction of the basics of HTPB composite propellantviscoelasticity is presented as well as the simulation of the mechanical relaxationphenomenon of the propellant material through quasi-static analysis, and thecorresponding material properties are given out. Second, propellant materialfracture criterion is derived using the finite element method, which verifies thefeasibility of extended finite element (XFEM) application to the propellantmaterial. Again, a model of pentagram shape grain without crack is established,using which the dangerous point of grains are calculated. Solidifying and coolingprocess of the pentagram shape grain with initial crack are analyzed using thefinite element method. Then the parameters of the crack changes as well as thepropellant grain debonding situations are calculated. Finally the crack extensionsituation of the initial crack-containing grain is analyzed under internal pressureusing the extended finite element method. And the internal pressure value,increasing to which the grain without initial crack will generate crack, as well asthe crack growth situation under this condition are calculated considering thematerial properties of the propellant.In this paper, the finite element method and the extended finite elementmethod are compared to analyse their respective advantages and disadvantages.This paper provides certain reference to the fracture behavior analysis of the solidpropellant grains, and will also provide guidance in practical applications.