Low Velocity Impact Analysis Research Articles

Low Velocity Impact and Compression-After-Impact Response of Z-Pin Reinforced Core Sandwich Composites

In the current work, sandwich composite structures with innovative constructions referred to as Z-pins, or truss core pins, are investigated. The Z-pin core sandwich construction offers enhanced transverse stiffness, high damage resistance, and multi-functional benefits. The present study deals with analysis of low-velocity impact (LVI) of Z-pin sandwich plate, and experimental studies of compression-after-impact characterization. Experimental studies on LVI of Z-pin sandwich plate considered in the analysis have been reported in Vaidya, et al., 1999, “Low Velocity Impact Response of Laminated Sandwich Composites with Hollow and Foam-Filled Z-Pin Reinforced Core,” Journal of Composites Technology and Research, JCTRER, 21, No. 2, Apr., pp. 84–97, where the samples were subjected to 11, 20, 28, 33, and 40 J of impact energy. The LVI analysis is developed with regards to Z-pin buckling as a primary failure mode (and based on experimental observations). A finite element model accounting for buckling of the pins has been developed and analyzed using ABAQUS. This paper also presents experimental results on compression-after-impact (CAI) studies which were performed on the sandwich composites with Z-pin reinforced core “with” and “without” foam. The experimental LVI tests were performed in Vaidya, et al., 1999, “Low Velocity Impact Response of Laminated Sandwich Composites with Hollow and Foam-Filled Z-Pin Reinforced Core,” Journal of Composites Technology and Research, JCTRER, 21, No. 2, Apr., pp. 84–97. The results indicate that selective use of Z-pin core is a viable idea in utilizing space within the core for sandwich composites in structural applications. [S0094-4289(00)02904-2]

Finite element analysis of low-velocity impact on composite sandwich plates

The response of composite sandwich plates to low-velocity impact is predicted by a displacement-based, plate bending, finite element algorithm. Fifth order Hermitian interpolation allows three-dimensional equilibrium integration for transverse stress calculations to be carried out symbolically on the interpolation functions so that transverse stresses within the elements are expressed directly in terms of nodal quantities. Nomex honeycomb sandwich core is modeled using an elastic–plastic foundation and contact loading is simulated by Hertzian pressure distribution for which the contact radius is determined iteratively. Damage prediction by failure criteria and damage progression via stiffness reduction are employed. Comparison to experimental low-velocity impact and static indentation data shows the ability to model some of the important features of static indentation of composite sandwich structures. In particular, the slope of the load displacement curve (stiffness), including contact, before damage is well represented. Core failure load is predicted by the analysis within 10% of the experimental value.

Low velocity impact analysis of composite sandwich shells using higher-order shear deformation theories

In the present investigation, higher-order and conventional first-order shear deformation theories are used to study the impact response of composite sandwich shells. The formulation is based on Donnell’s shallow shell theory. Nine-noded Lagrangian elements are used for the finite element formulation. A modified Hertzian contact law is used to calculate the contact force. The results obtained from the present investigation are found to compare well with those existing in the open literature. The numerical results are presented to study the changes in the impact response due to the increase of core depth from zero to some specified value and the changes in core stiffness for a particular core depth.

An analysis of low-velocity impact of spheres on elastic curved-shell structures

A solution method for dynamic analysis of low-velocity impact between elastic curved-shell structures and spheres is presented. The discretized nonlinear impact equations are derived based on the degenerated shell FE formulation and the Hertzian contact theory. They are numerically integrated to get various transient responses such as contact force and other field quantities. The validity and applicability of the method are shown numerically with two model problems of practical importance.

Low velocity impact analysis with nastran

A nonlinear elastic force-displacement relationship is used to calculate the transient impact force and local deformation at the point of contact betewen impactor and target. The nonlinear analysis and transfer function capabilities of NASTRAN are used to define a finite element model that behaves globally linearly elastic, and locally nonlinear elastic to model the local contact behavior. Results are presented for two different structures: a uniform cylindrical rod impacted longitudinally; and an orthotropic plate impacted transversely. Calculated impact force and transient structural response of the targets are shown to compare well with result measured in experimental tests.

Analysis of Simply-Supported Orthotropic Plates Subject to Static and Dynamic Loads

Equations are presented for the analysis of simply-supported orthotopic plates subjected to static and dynamic loading conditions. Transient loading conditions considered include sine, rectangul ar, and triangular pulses, and pulses r epresentative of high explosive blast and nuclear blast. These pulses can be applied as a uniform load over the panel, a c oncentrated load, a uniform l oad applied over a small rectangular area and a c osine loading a pplied over a small rectangular area. A method for the analysis of low velocity impact is also presented.