Sandwich-structured composite

About: Sandwich-structured composite is a research topic. Over the lifetime, 5853 publications have been published within this topic receiving 101126 citations.

Evaluation of sandwich panels with various polyurethane foam-cores and ribs

Abstract: The objective of this study was to evaluate three potential core alternatives for glass fiber reinforced polymer (GFRP) foam-core sandwich panels. The proposed system could reduce the initial production costs and the manufacturing difficulties while improving the system performance. Three different polyurethane foam configurations were considered for the inner core, and the most suitable system was recommended for further prototyping. These configurations consisted of high-density polyurethane foam (Type 1), a bidirectional gridwork of thin, interconnecting, GFRP webs that is in-filled with lowdensity polyurethane foam (Type 2), and trapezoidal-shaped, low-density polyurethane foam utilizing GFRP web layers (Type 3). The facings of the three cores consisted of three plies of bidirectional E-glass woven fabric within a compatible polyurethane resin. Several types of small-scale experimental investigations were conducted. The results from this study indicated that the Types 1 and 2 cores were very weak and flexible making their implementation in bridge deck panels less practical. The Type 3 core possessed a higher strength and stiffness than the other two types. Therefore, this type is recommended for the proposed sandwich system to serve as a candidate for further development. Additionally, a finite element model (FEM) was developed using software package ABAQUS for the Type 3 system to further investigate its structural behavior. This model was successfully compared to experimental data indicating its suitability for parametric analysis of panels and their design.

Experiment assessment of the ballistic response of composite pyramidal lattice truss structures

Abstract: Sandwich panels with lattice cores have attracted significant interest as multifunctional structures. The lattices consist of 3D repeating unit cells constructed from plates or trusses oriented to efficiently support applied stresses. These systems show promise for supporting structural loads and mitigating the blast effects of explosions. Here, a preliminary study has been conducted to investigate the ballistic behavior of a model lattice and to explore the effect of filling the lattices void spaces with polymers and ceramics. A sheet folding and brazing method has been used to fabricate pyramidal lattice truss structures from 304 stainless steel. The impact response of the various panels was assessed after impact by spherical, 12 mm diameter, 6.9 g projectiles with an incident, zero obliquity velocity of ∼600 m/s. Empty lattice sandwich panels with an areal density of 27.7 kg m−2 do not prevent the perforation of the sandwich panel. The impact with proximal face sheet reduced the projectile velocity to ∼450 m/s (by about 25%). Interactions with the lattice trusses and the distal face sheet further slowed the projectile resulting in an exit velocity at the distal face sheet of ∼360 m/s. The projectiles energy was dissipated by face sheet plastic dishing and fracture by petaling, and by truss plastic deformation. Infiltration of the lattice with polyurethane elastomers further reduced the projectile exit velocity. The strength of the effect depended upon the modulus of the polymer (and therefore its glass transition temperature, Tg). Only high modulus (high Tg) elastomers fully arrested the projectile. The energy of the projectile in this case was dissipated by a combination of face sheet stretching and polymer deformation and fracture. Low modulus elastomers reduced the projectile exit velocity by about 45% (to ∼250 m/s) and also resulted in resealing of the projectile path within the sandwich panel core. The incorporation of ballistic fabric within the polymer infiltrated systems had little effect on the ballistic resistance. A hybrid sample containing metal encased Al2O3 prism inserts provided the greatest resistance to penetration. In this case the projectiles were arrested within a sphere diameter of the sample front surface. Several of these hybrid systems offer promise as multifunctional, ballistic resistant, load-bearing structures.

Benefits of metal foams and developments in modelling techniques to assess their materials behaviour: a review

Abstract: A review assessing the relative benefits of metal foam core sandwich panels with respect to honeycomb, polymeric foam and truss cores has been conducted. It is noted that metal foams are able to combine low density with good bending stiffness and strength, making them attractive core materials for use in industrial applications (e.g. aircraft wing structures). The current modelling tools available for metal foams are also reviewed. These fall under three categories: analytical methods using dimensional analysis, finite element methods utilising a repeating unit cell, and finite element methods utilising the random Voronoi technique. It is noted that analytical methods do not take into account the effect of imperfections in the microstructure. Finite element methods utilising a repeating unit cell also fail to capture the natural variations in microstructure that are observed in most cellular materials. The effects of imperfections are discussed, and it is observed that these reduce the hydrostatic...

Compression-after-Impact Strength of Sandwich Panels with Core Crushing Damage

Abstract: Compression-after-impact (CAI) strength of foam-cored sandwich panels with composite face sheets is investigated experimentally. The low-velocity impact by a semi-spherical (blunt) projectile is considered, producing a damage mainly in a form of core crushing accompanied by a permanent indentation (residual dent) in the face sheet. Instrumentation of the panels by strain gauges and digital speckle photography analysis are used to study the effect of damage on failure mechanisms in the panel. Residual dent growth inwards toward the mid-plane of a sandwich panel followed by a complete separation of the face sheet is identified as the failure mode. CAI strength of sandwich panels is shown to decrease with increasing impact damage size. Destructive sectioning of sandwich panels is used to characterise damage parameters and morphology for implementation in a finite element model. The finite element model that accounts for relevant details of impact damage morphology is developed and proposed for failure analysis and CAI strength predictions of damaged panels demonstrating a good correlation with experimental results.