Image-Based Inertial Impact (IBII) Tests for Measuring the Interlaminar Shear Moduli of Composites
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RESEARCH PAPER
Image‑Based Inertial Impact (IBII) Tests for Measuring the Interlaminar Shear Moduli of Composites J. Van Blitterswyk1 · L. Fletcher1 · F. Pierron1 Received: 28 February 2020 / Accepted: 15 July 2020 © The Author(s) 2020
Abstract The image-based inertial impact test has previously shown that inertial effects generated with high-strain-rate loading can be used to measure the dynamic constitutive properties of composites at strain rates on the order of 1600 s−1 . This work represents an important next step in exploring the potential of this concept with two tests presented where loading heterogeneity is exploited to measure the interlaminar shear modulus and stress–strain behaviour at high strain rates. The first test configuration used a short-beam with asymmetric loading to activate the shear behaviour. The virtual fields method was used to directly identify the interlaminar shear modulus from heterogeneous full-field maps of strain and acceleration. Simulated experiments were used to optimise the test configuration, select optimal smoothing parameters, and quantify uncertainty from grid rotation on the shear modulus identifications. The test was validated experimentally with three different virtual fields identifying an average shear modulus ranging from 5.7 to 5.9 GPa measured at 1600 s−1 , representing a 16–19% increase compared to quasi-static measurements. The shear modulus could also be identified from shear introduced into specimens tested in the standard, end-on interlaminar IBII configuration from slight in-plane misalignments of the impactor. The identified value of 5.6 GPa validates measurements from the first configuration and also demonstrates the capability to identify multiple interlaminar stiffness parameters from a single test. Keywords Image-based inertial impact (IBII) test · High strain rate · Interlaminar shear properties · Fibre-reinforced polymer composites · Ultra-high-speed imaging · Virtual fields method
Introduction Due to the high specific stiffness and strength of polymer–matrix composites, there is an increasing desire to use thicker composite structures as lightweight alternatives to their metallic counterparts. In these cases, the interlaminar stresses become important to consider due to the relatively Electronic supplementary material The online version of this article (https://doi.org/10.1007/s40870-020-00258-4) contains supplementary material, which is available to authorized users. * J. Van Blitterswyk j.van‑[email protected] L. Fletcher [email protected] F. Pierron [email protected] 1
Mechanical Engineering, University of Southampton, Southampton SO17 1BJ, UK
low strength and stiffness in these material planes, which leads to increased susceptibility to micro-cracking or delaminations, and premature failure of the material. Moreover, these structures are often subjected to dynamic loading (e.g., blast, crash, foreign object strike, etc.) where significant interlaminar stresses can develop over a range of strain rates [1–3]. There
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