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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.
Response and Damage Tolerance of Composite Sandwich Structures under Low Velocity Impact
Experimental Mechanics, 2012
The deformation and failure response of composite sandwich beams and panels under low velocity impact was reviewed and discussed. Sandwich facesheet materials discussed are unidirectional and woven carbon/ epoxy, and woven glass/vinylester composite laminates; sandwich core materials investigated include four types of closed cell PVC foams of various densities, and balsa wood. Sandwich beams were tested in an instrumented drop tower system under various energy levels, where load and strain histories and failure modes were recorded for the various types of beams. Peak loads predicted by springmass and energy balance models were in satisfactory agreement with experimental measurements. Failure patterns depend strongly on the impact energy levels and core properties. Failure modes observed include core indentation/ cracking, facesheet buckling, delamination within the facesheet, and debonding between the facesheet and core. In the case of sandwich panels, it was shown that static and impact loads of the same magnitude produce very similar far-field deformations. The induced damage is localized and is lower for impact loading than for an equivalent static loading. The load history, predicted by a model based on the sinusoidal shape of the impact load pulse, was in agreement with experimental results. A finite element model was implemented to capture the full response of the panel indentation. The investigation of post impact behavior of sandwich structures shows that, although impact damage may not be readily visible, its effects on the residual mechanical properties of the structure can be quite detrimental.
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.
2016
Gondaliya, Ravi MSAE, Embry-Riddle Aeronautical University, March 2016. Improving Damage Tolerance Of Composite Sandwich Structures Subjected To Low Velocity Impact Loading: Experimental And Numerical Analysis Sandwich structures with composite facing skins have seen applications in variety of sectors including aerospace and automobile, owing to their high specific mechanical properties. However, there is a need to develop better damage tolerant sandwich structures since conventional composite facing skins exhibit low impact resistance in the transverse direction. Here, composite skin sandwich structures with three different impact resistant core materials were fabricated and tested both experimentally and numerically. Neat CFRP and 2024-T3 aluminum alloy sheets were also investigated. Cores utilizing impact resistant D3O were found to have very favorable weight specific energy absorbing properties at higher impact velocities as compared to those made from Nomex or Sorbothane cores....
Design and Fabrication of Equipment for Low Velocity Impact Testing of Composite Sandwich Panels
2011
Polymer composite sandwich panels are being utilized increasingly as primary load-carrying components in aircraft and aerospace structures. Serving in this capacity, these structures are subjected to impacts such as tool drops, hail, bird strikes, and runway debris. Unlike for their solid metallic counterparts, predictions of the effects of low-velocity impact damage are difficult and are still relatively immature. Sandwich panels in particular are sensitive to localized impact. For making a systematic study of impact on composite sandwich panels under these conditions, suitable equipment was designed and fabricated. This article describes the salient features of indigenously developed test equipment for testing localized, penetrating impact on sandwich panels. The size of the sandwich panels in question are 150 X 150 mm 2 with a typical thickness of 16 - 25 mm. The impact velocities are in the region 2 - 6 m/s, with an impactor mass between 2.5 and 12.5 kg, and two types of impacto...
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.
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.
Impact properties of aluminium - glass fiber reinforced plastics sandwich panels
Materials Research, 2012
Aluminium-glass fiber reinforced plastics (GFRP) sandwich panels are hybrid laminates consisting of GFRP bonded with thin aluminum sheets on either side. Such sandwich materials are increasingly used in airplane and automobile structures. Laminates with varying aluminium thickness fractions, fiber volume fractions and orientation in the layers of GFRP were fabricated by hand lay up method and evaluated for their impact performance by conducting drop weight tests under low velocity impacts. The impact energy required for initiating a crack in the outer aluminium layer as well as the energy required for perforation was recorded. The impact load-time history was also recorded to understand the failure behavior. The damage depth and the damage area were measured to evaluate the impact resistance. Optical photography and scanning electron micrographs were taken to visualize the crack and the damage zone. The bidirectional cross-ply hybrid laminate (CPHL) has been found to exhibit better impact performance and damage resistance than the unidirectional hybrid laminate (UDHL). Increase in aluminium thickness fraction (Al tf) and fiber volume fraction (V f) resulted in an increase in the impact energy required for cracking and perforation. On an overall basis, the sandwich panels exhibited better impact performance than the monolithic aluminium.
Thermomechanical behaviour of composite sandwich panels of polymer/metal under low-velocity impact
This work deals with the mechanical behavior under impact loading (5 m/s ≤ V0 ≤ 15 m/s) and different temperatures (15°C and 100°C) of the three-layered sandwich sheets: metal skins (2024 aluminum alloy) and polymer core (PEEK). This type of configurations are widely used in automobile sector. In order to conduct the perforation tests a drop weight tower CEAST INSTRON 9350 with climatic chamber has been used. Numerical analysis using Johnson Cook (JC) plasticity for thermoplastic PEEK polymer has been implemented. This model considers temperature sensitivity between transition temperature and melting temperature. The amount of kinetic energy of the striker converted into plastic work is strongly dependent on the initial temperature.