Rheological effects in in-plane shear test and in-plane shear reep test on glass-vinyl-ester lamina
Marian Klasztorny, Daniel B. Nycz, Pawel Bogusz
Quarterly No. 1, 2020 pages 35-42
DOI:
keywords: fibre-reinforced polymer-matrix composite, balanced orthogonal stitched fabric, vinyl-ester resin, in-plane shear test, in-plane shear creep test, rheological effects
abstract The research concerns an E-glass/vinyl-ester composite reinforced with a balanced orthogonal stitched fabric. According to the EN ISO 14129 standard, the in-plane shear modulus and in-plane shear strength for this composite type are identified from a ±45o off-axis tension test at the crosshead displacement rate of 2 mm/min. The study presents the results of experimental quasi-static ±45o off-axis tension tests in a small shear strain range, aimed at demonstrating that the high nonlinearity of the shear stress-shear strain curve is caused by viscoelastic flow of the resin at low levels of shear stress and by viscoelastic flow and plastic micro cracks of the resin at high levels of shear stress. The tests were conducted applying four quasi-static displacement rates. It was shown that the shear stress-strain curve course and the shear strength value strongly depend on the crosshead displacement rate. To confirm the nonlinearity explanation, a classic short-term (1 hour) in-plane shear creep test was carried out on ±45o off-axis specimens subjected to in-plane shear stress equal to 67% of the average in-plane shear strength calculated according to the EN ISO 14129 standard. The ply sequence blocking viscoelastic flow and plastic micro cracks of the resin was recommended.