Effect of strain rate on the mechanical properties of polycarbonate processed by compression and injection molding

Abstract

The high impact strength of polycarbonate has been studied and exploited for many applications. However, the interaction between processing-induced effects and the strain rate affects the mechanical behavior significantly. In this work, the effects of the processing-induced thermal history, generated by either injection molding or compression molding, were characterized. Polycarbonate samples manufactured with the two processes were experimentally compared using quasi-static and dynamic compression testing. The processing effects are further evaluated by combining a numerical calculation of the temperature history and a constitutive model to predict the yield strength of the glassy polymer. The constitutive modeling approach considers both the effect of the rate-dependent and stress-activated motion of the chain segments, and the strain-hardening effect due to molecular alignment. The results indicate that the thermal history has a significant effect at low strain rates, while its influence is negligible in the dynamic range. The modeling effort allows estimating the yield strength with different accuracy depending on the strain rate values.

The Effect of Notch and Molecular Weight on the Impact Fracture Behavior of Polycarbonate

“…PC is frequently used in impact protection applications [ 1 ], including aircraft canopies [ 2 ], face shields, goggles, and blast shields. Thus, the impact response of PC products [ 3 , 4 ] is a highly worthy research topic. Molecular weight is a key parameter that affects the physical, mechanical, and processable properties of polymers, and directly determines the application of the product, as well as PC.…”

Experimental and constitutive analyses of the stress relaxation behavior of glassy polymers

“…that exist among the molecular chains in the glassy state. [17,18] The large number of secondary bonds is also an important reason for the brittle fracture of glassy polymers, as it raises the energy barrier for chain conformation transition (rotation of the chain around its C C bonds) and causes frozen chain segment motions. If the segment motions are activated by applied stress or thermal energy, [19,20] the yield/flow may occur and the polymer may become ductile.…”