Study of the stress state of polycarbonate monolithic sheets using optical-polarization methods

Objectives. The study assessed the possibility of using optical-polarization methods to test quantitatively the stress state and residual stress in polycarbonate (PC) monolithic sheets. This stress is the leading cause of the cracking of PC sheets and the products made of them.

Methods. The objects were samples of monolithic PC sheets made by various manufacturers (Monogal and Novattro). The birefringence method was used to study the stress state of the samples, and the interference images obtained in polarized light in crossed polaroids were analyzed.

Results. The efficiency of optical-polarization research methods, such as the birefringence and the analysis of the interference images of stretched PC samples combined into an additive spectrum, was shown. The residual stress in the monolithic PC sheets made by various manufacturers was estimated.

Conclusions. The quantitative relationship between the stress acting on the PC samples, their birefringence, and the characteristics of their additive spectrum of interference images of stressed samples obtained in polarized light in crossed polaroids was established. The possibility of a quantitative assessment of the residual stress in monolithic PC sheets based on an analysis of their additive spectrum of interference images was shown. The measured residual stress did not exceed 1 MPa.

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