Showing papers by "Michael May published in 2014"
TL;DR: In this article, an experimental and numerical study of composite T-joints under quasi-static and high-rate dynamic loading is presented, focusing on the investigation of a novel reinforcement technique in the through-thickness direction using metallic arrow-pins to increase failure resistance and damage tolerance.
73 citations
TL;DR: In this article, a rate-dependent constitutive law for cohesive interface elements is introduced for the adhesive considering both, the rate dependency of the initiation stress and the rate dependencies of the fracture toughness.
64 citations
TL;DR: In this paper, a computationally efficient adaptive multi-scale methodology for modeling composites under high rates of loading is proposed, which relies on micromechanical properties of the constituents only.
Abstract: A computationally efficient adaptive multi-scale methodology for modeling composites under high rates of loading is proposed. The physically based model relies on micromechanical properties of the constituents only. The adaptive algorithm switches between two different constitutive laws. Initially, the material response is calculated based on effective linear-elastic, orthotropic material properties at the ply scale which are calculated using the rule of mixtures. A modified Hashin–Rotem criterion is then used to identify the switch to a more accurate micromechanical analysis based on the generalized method of cells (GMC). The methodology is verified by simulating tensile tests on laminates with different stacking sequences. Finally the model validated against experimental data for high-velocity impact on quasi-isotropic composite targets taken from the literature in order to illustrate the efficiency and accuracy of the proposed methodology.
21 citations
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TL;DR: In this article, the similarity of meshless discretizations of Peridynamics and Smooth-Particle-Hydrodynamics (SPH) was discussed, and it was shown that the discretized equations of both methods coincide if nodal integration is used.
Abstract: This paper discusses the similarity of meshless discretizations of Peridynamics and Smooth-Particle-Hydrodynamics (SPH), if Peridynamics is applied to classical material models based on the deformation gradient. We show that the discretized equations of both methods coincide if nodal integration is used. This equivalence implies that Peridynamics reduces to an old meshless method and all instability problems of collocation-type particle methods apply. These instabilities arise as a consequence of the nodal integration scheme, which causes rank-deficiency and leads to spurious zero-energy modes. As a result of the demonstrated equivalence to SPH, enhanced implementations of Peridynamics should employ more accurate integration schemes.
15 citations
TL;DR: In this paper, a non-linear orthotropic material model for the UHMWPE, based on the product DYNEEMA ® HB26, is used for assessing the influence of the material properties on the ballistic performance.
Abstract: Ultra-high molecular weight polyethylene (UHMWPE) has a high potential for ballistic armor applications due to the excellent weight specific strength inherent to this type of material. In this paper, a non-linear orthotropic material model for the UHMWPE, based on the product DYNEEMA ® HB26, is used for assessing the influence of the material properties on the ballistic performance. The model, implemented in the commercial hydrocode ANSYS AUTODYN uses initially linear-orthotropic elasticity, subsequent non-linear strain hardening, multiple stress-based composite failure criteria and post-failure softening. The strength model is coupled with a polynomial equation of state. An experimentally supported material data set for UHMWPE, presented before, is used as a baseline for the numerical studies on high velocity impact. Parameter sensitivities are studied for these impact situations. The numerical predictions are compared to available experimental data over a wide range of impact velocities (1 km/s up to 6 km/s). The objective of this paper is to assess the influence of different material parameters on the predictive capability of high velocity impact simulations and subsequently provide guidelines for the required experimental
7 citations