Low-Velocity Impact Dynamic Behavior of Laminated Composite Nonprismatic Folded Plate Structures

In this paper, the higher-order shear deformation theory is used to study the response of graphite/epoxy laminated composite nonprismatic folded plates subjected to impact loads. A finite-element model of the theory is also developed. The modified Hertzian contact law incorporated within the Newton–Raphson method is used to calculate the contact force between the impactor and the laminated plate. For time integration, the Newmark direct integration was adopted. Numerical results are presented to demonstrate the effects of span-to-thickness ratio, fiber angle, stacking sequence, and crank angle on the response of laminated plate subjected to impact. It is demonstrated that the results obtained from the present investigation compare well with those reported in the open literature.     

Performance Evaluation of Repair Technique for Damaged Fiber-Reinforced Polymer Honeycomb Bridge Deck Panels

All-composite, fiber-reinforced polymer honeycomb (FRPH) sandwich panels are an innovative application of modern composite materials in civil engineering. These panels have become increasingly popular for use as full-depth bridge decks and have been used to span both transversely between steel or concrete girders and longitudinally between abutments. Although several bridges using FRPH panels have been installed in recent years, a method to repair the panels if they are damaged has not been thoroughly investigated. This paper presents the analysis and full-scale evaluation of a 9.75 m (32 ft) long FRPH member that was subjected to severe core-face delamination damage and subsequently repaired. As such, the work presented herein is the first of its kind to be conducted for FRPH bridge members. The damaged member when repaired was shown to have approximately 65% more capacity than a similar undamaged member. The additional capacity was achieved using a single wrapping layer over the face plates and sinusoidal core. This wrapping layer is believed to have prevented a failure (at the resin bond line) between the face plates and core by engaging a shear-friction type clamping force. The contribution of the wrap layer is considered using simple calculations, rigorous finite-element models, and experimental data. Acoustic emission monitoring was used to compare the performance of the damaged and repaired specimens under sustained load.     

Explicit Finite-Element Analysis of 2024-T3/T351 Aluminum Material under Impact Loading for Airplane Engine Containment and Fragment Shielding

Uncontained aircraft engine failure can cause catastrophic damaging effects to aircraft systems if not addressed in the aircraft design. Mitigating the damaging effects of uncontained engine failure and improving the numerical modeling capability of these uncontained engine events are crucial. In this paper, high strain rate material behavior of one of the most extensively used materials in the aircraft industry is simulated and the results are compared against ballistic impact tests. Ballistic limits are evaluated by utilizing explicit finite-element (FE) simulations based on the corresponding ballistic impact experiments performed at different material thicknesses. LS-DYNA is used as a nonlinear explicit dynamics FE code for the simulations. A Johnson–Cook material model with different sets of parameters is employed as a thermo-viscoplastic material model coupled with a nonlinear equation of state and an accumulated damage evaluation algorithm for the numerical simulations. Predictive performance of the numerical models is discussed in terms of material characterization efforts, material model parameters, mesh sensitivities, and effects of stress triaxiality. It is shown that mesh refinement does not necessarily provide better results for ballistic limit simulations without considering and calibrating these interrelated factors. Moreover, it is shown that current models that can only fit a specific function for damage evaluation as a function of stress triaxiality are not always successful in predicting failure, especially if the state of stress changes significantly.