The Fracture Energy and Some Mechanical Properties of a Polyurethane Elastomer

Abstract

synopsisThe energy required to form a unit of new surface in the fracture of a polyurethane elastomer is determined.The rate sensitivity of the material has been reduced by swelling it in toluene. This paper primarily describes the experimetal work of measuring the lower limit of the fracture energy. With this value and the creep compliance as a basis, the rate dependence of fracture energy for the unswollen material has been determined. It is thus shown that the dependence of the fracture energy on the rate of crack propagation can be explained by energy dissipation around the tip of the crack. Good agreement between the theoretically and experimentally determined relationships for the rate-sensitive fracture energy is demonstrated.

Crack Propagation in a Linearly Viscoelastic Strip

“…The values of t he shlft factors <f> 7 • for the test temperatures given in Fig. 5 are in good agreement wit h values determined by other test~ [22,24]. The actually ob erved relationship between strain Eo, crack velocit.y v, a nd temperat.ure T is seeu to be well represented by eriuation ( 18), toget.her with t he material proper ties just discussed.…”

“…This can be accomplished by measuring S for very small crack velocities at temperatures well above t he glass transition te mperat ure or by swelling the material in a suita ble solvent and testing it in t his state [22,24]. Both methods were applied to determi ne the intrinsic fracture e nergy of Solithane 50/ 50 and led to t he value S = 0.1 lb/ in.…”

Dynamic fracture of simulated solid propellant

“…We follow previous work, e.g., [6], and wish to evaluate the energy available for creation of new surfaces.…”

Threshold Tear Strength of Some Molecular Networks

“…When dissipative processes are minimized, the tear strength of elastomeric materials is found to reach a lower limit, termed here the threshold strength (1,2). Experimentally, the threshold strength is reached at high temperatures, at low rates of tearing and when the material is highly swollen with a low-viscosity liquid.…”