No abstract

Quasi-static punch-shear tests are carried out on plain weave (PW) S-2 glass/SC-15 epoxy composite laminates with a right circular cylinder punch to identify the sequence and extent of damage and the corresponding displacements at which they occur for a wide range of laminate thicknesses. Two different support spans of 25.4 mm (1 in) and 101.6 mm (4 in) diameter with different layers (0.6 mm ply thickness) of composite laminates are tested under quasi-static loading to identify compression-shear and tension-shear dominated modes of damage. Numerical punch shear experiments are conducted using LS-DYNA 970. The numerical modeling is carried out using a newly developed composite damage model, namely MAT 162, which has been incorporated into LS-DYNA. MAT 162 uses damage mechanics principle for progressive damage and material degradation. Input data required in MAT 162 have been calibrated to match the experimental results of 22-layer composite plate of both spans (25.4 mm and 101.6 mm). The calibrated material properties have been used to simulate other thicknesses, and the simulated results show good agreement with experiment results. It has been found that the dominant damage mechanisms are delamination and fiber breakage due to shear and tension.

No abstract

No abstract

Space-coiling acoustic metasurfaces have been largely exploited and shown their outstanding wave manipulation capacity. However, they are complex in realization and cannot directly manipulate acoustic near-fields by controlling the effective path length. Here, we propose a comprehensive paradigm for acoustic metasurfaces to extend the wave manipulations to both far- and near-fields and markedly reduce the implementation complexity with a simple structure, which consists of an array of deep-subwavelength-spaced slits perforated in a thin plate. A semi-analytical approach for such a design is established using a microscopic coupled-wave model, which reveals that the acoustic diffractive pattern at every slit exit is the sum of the initial transmission and the secondary scatterings of the coupled fields from other slits. For proof-of-concept, we examine two metasurface lenses for sound focusing within and beyond the diffraction limit. This work provides a feasible strategy for creating ultra-compact acoustic components with versatile potentials.