Abstract
This study aims to explain the effect of high strain rate torsion on unidirectional fiber glass / epoxy composite with and without adding nano particles (carbon and alumina) with weight percentage 2% and study the effect of the temperature and humidity on the samples under torsion dynamic test. Using the torsional Hopkinson split bar to testing under angle of the twist θ=10°. It can noticed that the maximum of the shear (stress, strain) of the composite increased with adding nano particles by rate of (24.8%, 3.2%) with added 2% nano carbon and (26%, 8.5%) with added 2% nano alumina, where the shear stress, shear strain and shear strain rate of all samples decreased with increasing (temperature and humidity) with different percentages. Finally, it was modifying Johnson-Cook constitutive model by adding parameter represented the humidity effect to simulate the experimental results, and then it was found the error percentages between the experimental results and theoretical results which range (0.0044% and 15.5%).
Highlights
In a lot of engineering applications the materials loaded at strain rate from quasi-static loading which ranges10−5 s−1 to dynamic loading at strain rate 103 s−1 while the hydraulic machines which used normally to testing material at strain rates up to 5 s−1 [1]
The experimental results progress the information needed for NASA scientists to development which can hgfgh98`1 it be used in the design. using a torsional split Hopkinson bar to testing three types of epoxy resins (PR-520, E-862 and 977-2 ) under shear stress at different strain rates with ranges (5x10−5 to 2 and 400 to 1000) s−1 and the temperature testing used at room temperature and 80°C
The results shown that all the strain rate used and temperatures significantly effect on the response of epoxy and the maximum shear stress decrease when the temperature increased and increased with increased strain rate for all resins, for example the shear stress increased from 48 Mpa to 85 Mpa when the strain rate increased from 1.3x10−4s−1 to 700 s−1 for E-862
Summary
In a lot of engineering applications the materials loaded at strain rate from quasi-static loading which ranges10−5 s−1 to dynamic loading at strain rate 103 s−1 while the hydraulic machines which used normally to testing material at strain rates up to 5 s−1 [1]. Hopkinson pressure bar (SHPB) device is using to make high strain rate that involve strain rate range (102 to 104) s−1 for testing material. Glenn (2003)[4] studied the effect of strain rate on mechanical response of three types of epoxy resins. Using a torsional split Hopkinson bar to testing three types of epoxy resins (PR-520, E-862 and 977-2 ) under shear stress at different strain rates with ranges (5x10−5 to 2 and 400 to 1000) s−1 and the temperature testing used at room temperature and 80°C. M. Nabil Bassim (2012) [5] used torsional split Hopkinson bar to test high strength steel with high strain rates .The specimen was forming from thin walls with two hexagonal ends.
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