Derived Dynamic Ply Properties from Test Data on Angle Ply Laminates

Dynamic unidirectional tensile ply properties were extracted from the results of burst tests on angle ply filament wound GRP and KRP tubes under internal hoop loading. The extracted longitudinal and transverse tensile strengths as well as transverse tensile moduli exhibited strain-rate sensitivities. Shear properties were derived from test results on 55° and 65° tube angles. Derived shear stress-strain curves and shear strength values are presented at different strain rates; again clearly demonstrating rate effects on these properties. Complete sets of strain rate dependent lamina tensile properties are presented for GRP and KRP covering the strain rate regime of 1 to 10² sec^-1.     

Tension behavior of unidirectional glass/epoxy composites under different strain rates

By considering wide applications of composite materials, having a proper knowledge of them under dynamic loading is necessary. In order to study the effects of strain rates on the behavior of the materials, special testing machines are needed. Most of the research in this field is focused on applying real loading and gripping boundary conditions on the testing specimens. In this study, behavior of unidirectional glass fiber reinforced polymeric composites under uni-axial loading is determined at quasi-static and intermediate strain rates of 0.001–100 s⁻¹. The tests were performed using a servo-hydraulic testing apparatus equipped with a strain rate increase mechanism. For performing the tests, a jig and a fixture are designed and manufactured. The performance of the test jig was evaluated and found to be adequate for testing of composites. Dynamic tests results are compared with the results of static tensile tests carried out on specimens with identical geometry. Experimental results show a significant increase of the tensile strength by increasing the strain rate. The tensile modulus and strain to failure are also observed to increase slightly by increasing the strain rate.     

In-plane shear strength of a carbon/carbon composite at different loading rates and temperatures

The in-plane shear strength (IPSS) of a carbon/carbon composite (C/C) was measured at different loading rates and temperatures by compressing the double-notched specimen (DNS). The fracture surfaces were examined by scanning electron microscopy. The results indicate that IPSS measured by loading in compressing DNS is very close to that determined by the Iosipescu method at room temperature. There is a linear relationship between IPSS and the loading rate on the log-log coordinate, as the loading rate increases from 0.005 to 2 mm/min. IPSS at 1873 K is about two times of that at room temperature. The results were caused by the degassing effect of the absorbed water, release of the thermal stress and enhancement of the fiber strength.     

Deformation and fracture of high-temperature steels at different temperatures and loading rates

Charpy impact tests were conducted at different temperatures and loading rates. Temperature dependences of the crack initiation and propagation energies were determined for carbon steel 45, steels St. 3 and 15Kh2NMFA from the load-time curves obtained with due account of the impact test results. The effect of the loading rate on the temperature dependence of the impact toughness was analyzed within the range from 1 to 4.4 m/s. __________ Translated from Problemy Prochnosti, No. 1, pp. 29–34, January–February, 2009.