Strain rate influence on hardening and damage characteristics of composite materials
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O R I G I NA L PA P E R
Evgeny Lomakin
· Boris Fedulov · Alexey Fedorenko
Strain rate influence on hardening and damage characteristics of composite materials
Received: 13 June 2020 / Revised: 4 July 2020 / Accepted: 22 August 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract The paper presents models to characterize the dependence of hardening and strength characteristics of composite materials on damage and strain rate. The results of experimental studies of the behavior of composite materials in a wide range of strain rates are analyzed, and some regularities are determined. On the base of a failure criterion which includes the dependence of failure characteristics on damage and the rate of damage as well, taking into account the dependence of stiffness characteristics on the damage parameters, the stress–strain curves are determined for different strain rates, and they correlate quite well with the results of experimental studies. A method for the experimental determination of the material’s parameters is proposed. Some cases of complex, non-monotonic loading and unloading of composite materials are analyzed.
1 Introduction Experimental investigations of fiber-reinforced composite materials under impact show a strong dependency of the stiffness and strength characteristics on the loading rate. Hsiao and Daniel [1,2] used a split Hopkinson pressure bar (SHPB) for the off-axis tests of a unidirectional IM6G/3501-6 carbon/epoxy specimen. It was established that the strain rate increase from quasi-static mode to 1800 s−1 induces an initial transverse elastic modulus increase up to 37% and almost double failure stress for transverse compression. The initial shear modulus and failure stress increased up to 18% and 80%, correspondingly, with similar strain rate change, and highly nonlinear loading diagrams were observed. In Vogler and Kyriakides, study [3], shear and transverse compression strain rate dependency were observed in the strain rate range of ∼ 10−5 − 100 s−1 for AS4/PEEK composite. This range of strain rates was accomplished by a custom electromechanical testing machine, allowing biaxial shear-compression loading. Both pure shear and transverse compression loading diagrams had a linear initial segment, which was identical for the all strain rate levels up to a certain strain value, above which the stress–strain curves became nonlinear. Koerber et al. [4] used the SHPB method for the off-axis tests of IM7/8552 composite in conjunction with the digital image correlation (DIC) system for the E. Lomakin (B)· B. Fedulov Lomonosov Moscow State University, Moscow, Russia 119991 E-mail: [email protected] B. Fedulov E-mail: [email protected] E. Lomakin Moscow Aviation Institute, National Research University, Moscow, Russia 125993 B. Fedulov · A. Fedorenko Center for Design, Manufacturing and Materials, Skolkovo Institute of Science and Technology, Moscow, Russia 143025 E-mail: [email protected]
E. Lomakin et al.
strain measurements. The authors also noticed a significa
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