Response of Honeycomb Core Sandwich Panel with Minimum Gage GFRP Face-sheets to Compression Loading after Impact (original) (raw)
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Compression After Impact on Honeycomb Core Sandwich Panels with Thin Facesheets, Part 1: Experiments
53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference<BR>20th AIAA/ASME/AHS Adaptive Structures Conference<BR>14th AIAA, 2012
A two part research study has been completed on the topic of compression after impact (CAI) of thin facesheet honeycomb core sandwich panels. The research has focused on both experiments and analysis in an effort to establish and validate a new understanding of the damage tolerance of these materials. Part one, the subject of the current paper, is focused on the experimental testing. Of interest are sandwich panels, with aerospace applications, which consist of very thin, woven S2-fiberglass (with MTM45-1 epoxy) facesheets adhered to a Nomex honeycomb core. Two sets of specimens, which were identical with the exception of the density of the honeycomb core, were tested. Static indentation and low velocity impact using a drop tower are used to study damage formation in these materials. A series of highly instrumented CAI tests was then completed. New techniques used to observe CAI response and failure include high speed video photography, as well as digital image correlation (DIC) for full-field deformation measurement. Two CAI failure modes, indentation propagation, and crack propagation, were observed. From the results, it can be concluded that the CAI failure mode of these panels depends solely on the honeycomb core density.
Compression-after-Impact Strength of Sandwich Panels with Core Crushing Damage
Applied Composite Materials, 2005
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.
Experimental study of the medium velocity impact response of sandwich panels with different cores
Materials & Design, 2016
The impact response of sandwich panels is not only dependent on the facesheet but also on the core material. The choice of the core has a strong effect on the strength and durability of the structure. This paper compares the dynamic response of sandwich panels with different core materials when subjected to medium velocity impacts. The sandwich panels were made of aluminium facesheets with five different cores, viz., low density balsa wood, high density balsa wood, cork, polypropylene honeycomb, and polystyrene foam. All the specimens were impacted by a 384.4 g instrumented projectile with a hemispherical steel head at three impact energies of 43, 85 and 120 J. An accelerometer attached to the projectile and a high speed camera were used to collect data and record the impact process. 3D scanning technique was used to measure the deformation of front and back faces after impact. The impact properties of the sandwich panels with the five different cores were compared in terms of contact force, energy absorption, depth of indentation, overall bending deflection, etc. Post-mortem sectioning was also conducted to examine the impact induced failures such as facesheet rupture, crush of core material, and debonding between facesheet and core.
Damage Characterization of Polypropylene Honeycomb Sandwich Panels Subjected to Low-Velocity Impact
Advances in Materials Science and Engineering, 2013
The post-test deformation and failures of sandwich composites may involve complex interactions between various failure mechanisms. In this study, the extent of impact damages and response of the thermoplastic honeycomb sandwich are analysed through energy profile diagrams and associated load history curves. The degree of the postimpact damages of the sandwich is further characterized using an optical surfaces metrology analysis. The thickness of the honeycomb was found to influence the extent of the damage which occurred following the low-velocity impact. Thicker core was able to sustain a higher load as well as the energy absorption before total failure occurred.
Composites Part B: Engineering, 2012
In this paper, an analytical model for perforation of composite sandwich panels with honeycomb core subjected to high-velocity impact has been developed. The sandwich panel consists of a aluminium honeycomb core sandwiched between two thin composite skins. The solution involves a three-stage, perforation process including perforation of the front composite skin, honeycomb core, and bottom composite skin. The strain and kinetic energy of the front and backup composite skins and the absorbed energy of honeycomb core has been estimated. In addition, based on the energy balance and equation of motion the absorbed energy of sandwich panel, residual velocity of projectile, perforation time and projectile velocity have been obtained and compared with the available experimental tests and numerical model. Furthermore, effects of composite skins and aluminium honeycomb core on perforation resistance and ballistic performance of sandwich panels has been investigated.
Numerical modelling of the compression-after-impact performance of a composite sandwich panel
Journal of Sandwich Structures & Materials, 2015
A numerical model for the quasi-static indentation and compression-after-impact behaviour of a composite sandwich panel is presented, using cohesive surfaces for interlaminar damage prediction. Intra-laminar damage and core crushing is also included. The models show generally good agreement with experimental results for residual strength, performing best when two cohesive surfaces are used in the impacted skin, but tend to over-estimate the undamaged panel strength. Damage extent predictions from the indentation phase of the analysis are often quite poor, but do not necessarily correlate with the accuracy of the strength estimates. The model provides a promising basis for further development.
Impact response of integrated hollow core sandwich composite panels
Composites Part A-applied Science and Manufacturing, 2000
This paper deals with an innovative integrated hollow (space) E-glass/epoxy core sandwich composite construction that possesses several multi-functional benefits in addition to the providing lightweight and bending stiffness advantages. In comparison with traditional foam and honeycomb cores, the integrated space core provides a means to route wires/rods, embed electronic assemblies, and store fuel and fire-retardant foam, among other conceivable benefits. In the current work, the low-velocity impact (LVI) response of innovative integrated sandwich core composites was investigated. Three thicknesses of integrated and functionality-embedded E-glass/epoxy sandwich cores were considered in this study—including 6, 9 and 17 mm. The low-velocity impact results indicated that the hollow and functionality-embedded integrated core suffered a localized damage state limited to a system of core members in the vicinity of the impact. The peak forces attained under static compression and LVI were in accordance with Euler's column buckling equation. Stacking of the core was an effective way of improving functionality and limiting the LVI damage in the sandwich plate. The functionality-embedded cores provided enhanced LVI resistance due to energy additional energy absorption mechanisms.
Impact response of sandwich panels with polyurethane and polystyrene core and composite facesheets
Materials Today: Proceedings, 2019
An experimental study on the impact response of foam core sandwich panels subjected to low velocity impact is performed. Panels with glass fiber laminated facesheets and polystyrene and polyurethane foam core with density of 32 kg/m 3 , respectively 100 kg/m 3 , were tested in impact on an INSTRON Ceast 9340 drop tower at different impact energies. The composite facesheets were made of epoxy resin, glass fiber roving of 500 g/m 2 and short glass fibers of 3 mm in 5 different combinations. The effect of foam core and facesheet type on the resulting impact damage and contact force is analyzed. It was noted that higher impact energies introduce matrix damages and the partial fracture of the fibers which significantly change the force-displacement histories, particularly after the maximum impact force is reached. Also, the use of polyurethane foam core increased the impact damage indentation in size and depth compared to the panels with polystyrene core. Panels having facesheets only with short glass fibers show a very poor resistance compared to the ones with roving and are completely perforated even for the smallest impact energy.