Optimal blast mitigating sandwich structures with fiber-reinforced face sheets
Abstract
For fixed values of the areal mass density, and given (a) available fiber (glass, carbon, aramid), matrix (epoxy, vinyl ester), and core (balsa wood, PVC foam) materials, (b) values of their material parameters, (c) constraints on their geometries, (d) blast loads (AIREX, UNDEX), (e) the surrounding environment (air, water), and (f) uncertainties in values of material/geometric variables and boundary conditions, we propose to find optimal doubly-curved sandwich structures including (i) the number of cores, (ii) core materials, (iii) fiber material, fiber angle and matrix material in each lamina, the volume fraction of fibers, lamina thickness, and (iv) the confidence level of results so that energy dissipated is the maximum. The analysis will consider 3-dimensional damage initiation and propagation till structure’s ultimate failure. We will also determine locations of failure points, stress components significantly contributing to the failure, and confidence level of the results. We will analyze sandwich structure’s transient 3-dimensional deformations with a commercial finite element software, Abaqus, and employ the Tsai-Wu failure criteria, an optimization (e.g., genetic) algorithm, quantify effects of uncertainties in material parameters by the Latin hypercube method, and conduct sensitivity studies by using the analysis of variance (ANOVA) statistical technique and the JMP software. A user-defined subroutine, VUMAT, will be developed and its implementation in Abaqus will be verified by analyzing simple problems with known analytical solutions, and comparing with them predictions from the software. The predicted failure loads and failure point locations will be compared with those found in physical experiments. We will also explore strategies such as using (a) functionally graded core and face sheets, (b) surface modifications including bio-inspired, (c) metamaterials for the cores, (d) bumper shields, (e) adding polyurea layers, and (f) either imbedding viscoelastic layers or using viscoelastic material to bond different plies. We will find their optimal locations, thicknesses, and materials, to maximize the blast mitigation per unit areal mass density. The anticipated outcomes include an optimized geometry (face sheet thicknesses, core thickness, radii of curvatures), materials of face sheets (fiber angles, lamina stacking sequence), core (PVC foam, balsa wood), and the number of cores. The work when completed will favorably impact DoD capabilities in providing tools for designing light-weight impact-resistant sandwich structures for marine applications, and highly skilled work force for the DoD. The reduction in structure’s weight will either increase the pay load or make their operation more energy efficient.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 19, 2020
- Source ID
- N000142012876
Entities
People
- Romesh Batra
Organizations
- Office of Naval Research
- United States Navy
- Virginia Tech