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Research Papers

Energy-Absorbing Capacity of Polyurethane/SiC/Glass-Epoxy Laminates Under Impact Loading OPEN ACCESS

[+] Author and Article Information
G. Balaganesan

Department of Mechanical Engineering,
Indian Institute of Technology Madras,
Chennai 600036, India

V. Akshaj Kumar, V. C. Khan

Department of Mechanical Engineering,
Indian Institute of Technology Bhubaneswar,
Bhubaneswar 751013, India

S. M. Srinivasan

Department of Applied Mechanics,
Indian Institute of Technology Madras,
Chennai 600036, India
e-mail: mssiva@iitm.ac.in

1Corresponding author.

Contributed by the Materials Division of ASME for publication in the JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY. Manuscript received May 31, 2016; final manuscript received November 26, 2016; published online February 7, 2017. Assoc. Editor: Taehyo Park.

J. Eng. Mater. Technol 139(2), 021008 (Feb 07, 2017) (9 pages) Paper No: MATS-16-1159; doi: 10.1115/1.4035617 History: Received May 31, 2016; Revised November 26, 2016

This paper presents the energy absorption of target materials with combinations of polyurethane (PU) foam, PU sheet, SiC inserts, and SiC plate bonded to glass fiber reinforced composite laminate backing during impact loading. SiC inserts and SiC plates are bonded as front layer to enhance energy absorption and to protect composite laminate. The composite laminates are prepared by hand lay-up process and other layers are bonded by using epoxy. Low-velocity impact is conducted by using drop mass setup, and mild steel spherical nosed impactor is used for impact testing of target in fixed boundary conditions. Energy absorption and damage are compared to the target plates when subjected to impact at different energy levels. The energy absorbed in various failure modes is analyzed for various layers of target. Failure in the case of SiC inserts is local, and the insert under the impact point is damaged. However, in the other cases, the SiC plate is damaged along with fiber failure and delamination on the composite backing laminate. It is observed that the energy absorbed by SiC plate layered target is higher than SiC inserts layered target.

The use of composites for energy absorption in impact loading has received much attention [1]. Since use of these materials increases day-by-day and systems becoming complex, newer materials are developed or additional layers are bonded to improve the performance of the composites. In the recent years, researchers are involved to design lightweight structures with improved impact resistance as an alternative to traditional high hardened steel. The damage due to impact in laminated composite structures continues to be a major cause of concern. The composite materials are vulnerable to impact damage, which leads to significant reduction in strength. Therefore, understanding impact responses on vibration, energy absorption, and failure mechanisms and assessing residual strengths of the composite materials are necessary for the better use of these materials. The failure mechanisms in the fiber-reinforced composite materials depend on the parameters such as impact velocity, impact angle, geometry of the projectile, target material, target size, fiber orientation, laminate configuration, stacking sequence, and boundary conditions. The energy-absorbing mechanisms of polymer matrix fiber reinforced composites are due to elastic deformation of fibers, tensile failure of primary fibers, delamination, and matrix crack [2]. To design composite structures for ballistic impact application, it is important to understand and quantify the energy absorbed by each of these mechanisms [35]. It is observed that the energy absorbed due to deformation or deflection is maximum when compared to other modes of failures. Hence, some researchers [68] added additional layers like PU foam/sheet to enhance energy-absorbing capacity of target material. Presently, these sandwiched panels are widely used in automotive industry, civil engineering, packaging and transportation of fragile goods, and marine and aerospace industries. They have excellent lightweight properties, high stiffness and strength, ability to absorb energy during impact, damping characteristics, corrosion resistance, and improved fatigue life properties which make them a promising choice for the various lightweight impact resistant materials.

Zaretsky et al. [9] have studied the impact response of PU foams of high density and found that velocity after 43 m/s results in foam crush and some heat generation. Nasirzadeh and Sabet [10] studied on the impact response of sandwiched panel with various densities of PU foam. They found that foam density of 49 kg/m3 was optimum for ballistic application.

In armor applications, front facing hard ceramics are layered to protect backing composite materials. The ceramic materials used in the ballistic armors are Al2O3, B4C, SiC, and ceramic matrix composites. The most common composite backing materials include aramid woven fabrics, such as Kevlar and Twaron, and fiber glass materials such as S2-glass and E-glass [11,12].

The ceramic tiles possess high stiffness and hardness properties and hence have the capability to deform and erode the projectile to reduce its kinetic energy as well as transform itself into small fragments [13,14]. The backing materials must possess sufficiently high strength and toughness to absorb the residual kinetic energy of the projectile and prevent secondary impact from ceramic fragments [15,16].

An armor plate must fulfill two functions—a protective role and a structural role. Most of the researchers have studied only protective role, i.e., high-velocity impact of projectiles against front facing ceramic tiles with composite backing laminate. Benloulo and Sanchez-Galvez [17] proposed a simple one-dimensional analytical model to evaluate residual velocity, residual mass, projectile velocity, deflection, and strain histories of the backup material. They presented the first step in developing an analytical model of impact against ceramic/composite armors. Naik et al. [18] developed an energy-based dynamic analytical model for ballistic impact of ceramic-composite armor and found out that the residual velocity was in agreement with that of experimental results. They also discussed the various damage mechanisms and energy absorbed by the laminate and projectile in various modes of failure during impact. Lee and Yoo [19] concluded that an optimum value of the front ceramic tile to the aluminum back plate thickness ratio was 2.5. To capture different failure mechanisms, they made a numerical study using smoothed particle hydrodynamics which were matching with that of experimental results. Recently, Liu et al. [20] carried out experimental and numerical studies on hybrid sandwich structures for ballistic applications. They used front facing cylindrical ceramic inserts instead of square tiles and also used ultrahigh molecular weight polyethylene as core material. They observed very small damage in the backing material. Core material acts as a spacer for the stiff ceramic front layer by increasing moment of inertia and thus enhances the structural and ballistic performance of the armor [2123].

Many other researchers also have done low-velocity impact experiments on PU foam-core sandwich panels and concluded that sandwiched panel has higher energy-absorbing capacity than standalone composite/ceramic/metal laminates [2429].

So, it is important to analyze its behavior toward impact by heavy tools or foreign objects during maintenance and service. One important application of this study is the development of armor wall which is often impacted by heavy mass with low velocity. For example, wall impacted by a vehicle or a log of wood. There is no literature available for low-velocity impact with heavy mass on armor plate and this study can be considered as an initial step toward the development of armor materials capable of sustaining both ballistic and structural loads.

This study presents energy absorption of hybrid sandwich plates by various combinations made of SiC, PU sheet, PU foam, and glass fiber/epoxy composite backing when subjected to low-velocity impact. SiC inserts and SiC plates are bonded as front layer to enhance energy absorption and to protect composite laminate. The composite laminates are prepared by hand lay-up process and other layers are bonded by using epoxy. Low-velocity impact is conducted by using drop mass setup, and mild steel spherical nosed impactor is used for impact testing of target in fixed boundary conditions. Energy absorption and damage are compared for the target plates when subjected to impact at different energy levels. The energy absorbed in various failure modes is analyzed for various layers of target. Energy absorbed by PU sheet layered target is higher than PU foam layered target. SiC layer enhances energy-absorbing capacity of target materials. Failure in the case of SiC inserts is local, and the insert under the impact point is damaged. However, in the other cases, the SiC plate is damaged along with fiber failure and delamination on the composite backing laminate. It is observed that the energy absorbed by SiC plate layered target is higher than SiC inserts layered target.

Experiments were conducted to predict energy-absorbing capacity of target plates made by bonding of PU foam, PU sheet, SiC inserts, and SiC plate with glass fiber reinforced plastics (GFRP) laminate backing during impact loading. The composite laminates are prepared by hand lay-up process and other layers are bonded by using epoxy. Energy absorption of the laminates is obtained from initial and final velocity of the impactor measured during low-velocity impact conducted in a drop mass setup.

Specimen Fabrication.

Fiber-reinforced plastic composite laminate was made of three layers using woven roving mat (WRM) glass fiber of 610 gsm and epoxy LY556 and hardener HY951. The glass fiber reinforced plastics (GFRP) laminates were made by hand layup process with 0 deg/90 deg orientation of all the layers. The laminates were cut to the size of 150 mm × 150 mm by using circular saw cutter. Polyurethane foam (PUF) of density 450 kg/m3 and polyurethane sheet (PUS) of 10 mm thickness were cut into the size of 150 mm × 150 mm for bonding with GFRP laminates. GFRP, PU foam, and PU sheet layers were bonded in various configurations by using epoxy. The configuration of target materials PUF + GFRP, PUS + GFRP, GFRP + PUF + GFRP, and GFRP + PUS + GFRP laminates is shown in Figs. 1(a)1(d).

The hybrid sandwich specimens with front facing silicon carbide (SiC) ceramic plate were bonded to polyurethane foam and GFRP backing. Specimens were made using SiC plates of sizes 100 mm × 100 mm of 6 mm and 10 mm thickness, respectively. Another configuration of specimen consisted of SiC and aluminum inserts of size 25 mm × 25 mm and 6 mm thickness and was arranged as shown in Figs. 2(a) and 2(b). Aluminum inserts were used as dummy inserts, which are not subjected to impact. Bonding of different layers of materials with each other was done using epoxy resin.

Impact Test.

Low-velocity impact tests on specimens were conducted by using a drop weight tower as shown in Fig. 3. The specimens were hit orthogonally with an impactor which was accelerated freely in gravity through guide columns. The cylindrical impactor with a hemispherical nose of 16 mm in diameter was made of mild steel. A PCB (PCB Piezotronics Inc., Depew, NY) make load cell was equipped on the impactor head in order to register the impact force with reference to time. A rebound arrestor ensured to avoid multihits on the specimen by the impactor. Experiments were conducted for the impactor of mass 16 kg when dropped freely from the height of 0.5 m, 1 m, and 1.5 m. High-speed camera was used to capture the impact phenomenon and more importantly to measure the velocity of the impactor before and after the impact. The actual velocities measured are used to predict energy absorption of the target materials.

An analytical analysis is presented to find the layerwise energy-absorbing mechanisms of the target materials during low-velocity impact. The study is based on energy absorption principle. Incident energy of the impactor is lost during impact due to several energy-absorbing and damage mechanisms.

Energy lost by the impactor during impact is Display Formula

(1)El=KEiKEf

The energy lost by the impactor was equal to the energy absorbed by the deformations and damage mechanisms of target and the impactor. The energy absorbed by the layers of SiC, the PU foam/PU sheet, and the GFRP layer is analyzed.

Energy Absorbed by SiC Layer.

As the impact event progresses, the ceramic would be subjected to compression as well as tension. If the compressive stress exceeds the permissible limit, then compressive failure of ceramic would take place.

The energy density absorbed due to compression of ceramic layer is Display Formula

(2)Ecc=0εsbσccεcc dε

As the impactor strikes the ceramic, friction would be generated between the impactor and ceramic, as well as, the ceramic would be broken into tiny pieces. Gailly and Espinosa [30] explained the process of formation of tiny pieces from the ceramic plate as pulverization.

Energy Absorbed by PU Foam and PU Sheet.

During low-velocity impact, the front layer subjected to damage and thus core layer would absorb energy due to crushing as shown in Fig. 4. Hosseini and Khalili [31] discussed the energy dissipation in the foam by crushing during low-velocity impact on sandwich target. It is given in the below equation

Display Formula

(3)Ecp=πdi24qwop+49qwop(di2x)2

The PU foam layer and PU sheet would also absorb energy due to shear plugging [31] and this energy is Display Formula

(4)Esp=(πditp)(τp)(tp)

The energy density absorbed due to deformation of PU sheet layer is given by the below equation Display Formula

(5)Edefb=0εsbσsb(εsb)dεsb

Energy Absorbed by GFRP.

During the process of impact, the GFRP backing would fail due to elastic deformation, tensile failure of fibers, and delamination [5].

The composite backing would undergo primarily elastic deformation due to bending of target. The fibers near the impact zone would fail due to tension when the strains in fibers reach failure strain in tension.

Energy density absorbed by composite backing due to elastic deformation is Display Formula

(6)Edefb=0εsbσsb(εsb)dεsb

Energy density absorbed by composite backing due to tensile failure of fibers is Display Formula

(7)Etfb=0ε0bσb(εb)dεb

Energy density absorbed by composite backing due to delamination is Display Formula

(8)Edelamb=AdelamGIIb

Thus, from Eqs. (2)(8), the total energy lost by projectile during impact was Display Formula

(9)El=ESiC+Ecore+EGFRP

where Display Formula

(10)ESiC=Ecc
Display Formula
(11)Ecore=Ecp+Esp
Display Formula
(12)EGFRP=Edefb+Etfb+Edelamb

Energy Absorption in Target Material.

The target materials of size 150 mm × 150 mm are subjected to low-velocity impact for three different energy levels of 80 J, 160 J, and 240 J. These energy levels are obtained by dropping a mass of 16 kg from the height of 0.5 m, 1 m, and 1.5 m, respectively. The energy absorbed by the target materials during impact is determined based on the initial and residual kinetic energies of the impactor. The energy absorbed by three layer GFRP laminate is 17.73 J for incident energy of 80 J. The specimens prepared with the combinations of GFRP, PUF, and PUS were tested for all the three energy levels, and the energy absorbed in 80 J and 160 J is shown in Table 1. For incident impact energy of 80 J, the impactor rebounded when the experiment was conducted on PUS + GFRP laminate and it was found that the specimen absorbed 64.34 J of energy. It can be inferred that complete 80 J of energy was absorbed by the specimen and due to the elastic nature of PU sheet, it released energy and thus the impactor rebounded. In the case of PUF + GFRP, the impactor penetrated instead of rebounding and absorbed 48.58 J of energy. This is about 25% less when compared to PUS + GFRP specimen. For the specimen GFRP + PUF + GFRP, perforation failure occurred and absorbed 52.31 J of energy. GFRP + PUS + GFRP target laminate has absorbed 67.49 J of energy and penetration is observed in all the three layers. GFRP + PUS + GFRP laminate has absorbed 30% more energy than PUF layered laminate. The impactor in this case got stuck in the laminate instead of rebound. This is due to the friction between impactor and the front GFRP layer. In all the other cases, the impactor penetrated the sandwich specimen. There is no much difference between energy absorption between PUF + GFRP and PUS + GFRP when subjected to impact at 160 J of energy. At 160 J of incident energy, when additional layer of GFRP is bonded to the front face of PUF + GFRP, the increase in energy absorption is about 22%. This is slightly above when compared to individual GFRP laminate subjected to impact at 80 J of energy. At the same 160 J of incident energy, when GFRP is layered with PUS + GFRP, enhancement in energy absorption is 35%. This is due to increase in energy absorption in deformation mode.

Table 2 shows for energy absorption by the target material of all the configurations when subjected to impact at 240 J of incident energy. The energy absorbed by PUF + GFRP, PUS + GFRP, GFRP + PUF + GFRP, and GFRP + PUS + GFRP specimens is less when compared correspondingly to the incident energies of 80 J and 160 J. At low incident velocities and energy, impact duration between the laminate and the specimen is more, and thus, the specimens undergo deflection and absorb more energy. But, at higher incident velocities and energy, the failure modes or energy-absorbing phenomenon of the specimens are different due to less contact period. Hence, the deflection of the specimen decreases, which leads to the decrease in overall energy-absorbing capacity. PUS + GFRP laminate absorbs nearly 15% higher energy when compared to PUF + GFRP. When 6 mm thickness SiC plate is bonded in PUF + GFRP laminate, the energy absorption capacity of the laminate increases to three times the energy-absorbing capacity of PUF + GFRP. When 10 mm thickness SiC plate layered over PUF + GFRP laminate, the energy absorption is 12% higher than 6 mm SiC plate layered PUF + GFRP laminate. The energy absorption of 6 mm thickness SiC inserts layered PUF + GFRP laminate is 16% less when compared to 6 mm thickness SiC plate layered PUF + GFRP laminate. But damage is observed only in the insert which is layered at the point of impact.

Damage and Energy Absorbed in Each Failure Mode.

The layers of target material absorb energy in various failure modes when subjected to impact. The layer in the front face fails in the beginning and subsequently other layers. When the first layer is in the plastic limit, the backing GFRP laminate is subjected to load in the elastic limit. Each layer contributes to absorb impactor energy by its nature of failure. The GFRP laminate absorbs energy of impactor during deformation of secondary fibers, tensile failure of primary fibers, and delamination. PU foam fails by absorbing energy in crushing mode. PU sheet absorbs impactor energy by deformation and shear plugging. SiC plate and inserts absorb energy in compression.

Figure 5 shows the front, side, and rear views of the GFRP + PUF + GFRP laminate when subjected to impact at 160 J of incident energy. The fibers of the front GFRP laminate within the area covered by the diameter of the impactor failed. The delamination area of backing GFRP laminate is about 460 mm2. Petals of GFRP laminate are seen in the side and rear views in Fig. 5. Figure 6 shows the front, side, and rear views of the GFRP + PUS + GFRP laminate when subjected to impact at 160 J of incident energy. Delamination is observed in the surroundings of the impacted area in the front end GFRP laminate. This is due to deformation of target layers during impact. The delamination area in the back end GFRP is 7900 mm2 which is greater than the delamination area in the case of GFRP + PUF + GFRP. This is seen in Fig. 6. This is due to excessive deflection of the GFRP laminate at back end.

Figures 7 and 8 show the front, side, and rear views of the tested sandwich specimens at 240 J of incident energy. The delamination area of back end GFRP layer in GFRP + PUF + GFRP laminate is about 960 mm2, and the delamination area of backing GFRP layer in GFRP + PUS + GFRP laminate is 1500 mm2. The delamination area in FRP + PUS + FRP is greater than GFRP + PUF + GFRP because of stiffness variation in the core material. PU Sheet is more elastically deformable than PU Foam. This excessive deformation of PUS caused more delamination in composite backing when compared to specimen having PUF.

Figure 9 shows the energy absorption of PUS + GFRP laminate in various failure modes when subjected to impact energies of 80 J, 160 J, and 240 J. PU sheet absorbs about 46% impactor energy by crushing mode when it is subjected to impact energy of 80 J. For 160 J impactor energy, the energy absorbed by PU sheet in crushing is more than 50%. Energy absorbed by PU sheet in deformation mode is same in all the cases of impact energy. GFRP laminate absorbs maximum energy due to deformation of fibers which are not in the point of impact. The energy absorbed in tensile failure is same in all the cases which are due to same cross section of fibers that failed. The same energy-absorbing trend is seen in laminates of other configurations.

Figure 10 shows the front, side, and rear views of 6 mm thickness SiC plate layered PUF + GFRP laminate subjected to impact at 240 J of energy. Failure in SiC plate is observed in an area that is covered by the diameter of the projectile. Six radial cracks from point of impact to boundary were noticeable. Backing GFRP is failed due to deformation, delamination, and failure of fibers. The fibers failure is observed for more area than that is covered by the impactor diameter. This is due to stiffness and failure of SiC plate.

Figure 11 shows the front, side, and rear views of 10 mm thick SiC plate layered PUF + GFRP laminate subjected to impact at 240 J of energy. The failure of front end SiC plate and backing GFRP laminate is similar to 6 mm thickness SiC layered PUF + GFRP laminate. The delamination area of GFRP laminate at backing is higher than 6 mm plate layered specimen.

Figure 12 shows the front, side, and rear views of 6 mm thick SiC inserts layered over PUF + GFRP laminate and subjected to impact at 240 J of energy. Only the SiC insert that was bonded directly under the impact area is failed. This SiC insert is broken into fragments. Other SiC inserts are intact in their positions and there is no debonding of inserts. Backing GFRP is failed due to deformation, delamination, and failure of fibers.

Table 3 shows the energy absorbed by the target having front facing SiC layer in each mode of failure when they are subjected to impact at incident energy of 240 J. These values are calculated based on the equations in Sec. 3. It is observed that SiC absorbs maximum amount of energy during impact. During low-velocity impact, significant amount of energy is absorbed in elastic deformation of composite backing due to higher contact period. There is no debonding of layers observed in all the cases. It is found that PU foam absorbs energy in crushing and shear plugging mode. A small amount of energy is absorbed in deformation, tensile failure, and delamination in the backing GFRP laminate. For all the specimens, a marginal amount of energy is absorbed due to friction between impactor and laminate, scratches on the impactor, and matrix cracking in composite backing.

When 6 mm thickness SiC plate layered PUF + GFRP laminate is subjected to impact at 240 J of energy, 42% of the total impact energy is absorbed by the compression of ceramic layer. Foam layer absorbs 13% of energy in crushing and shear plugging mode. Further, the composite backing absorbs 14% of total energy due to elastic deformation and around 8% of energy is absorbed due to tensile failure of fibers and delamination.

The target with 10 mm thickness SiC layered PUF + GFRP laminate absorbs 62% of the total impact energy by the compression of ceramic layer. PU foam absorbs 11% of energy in crushing and shear plugging mode. Further, the GFRP backing laminate absorbs 12% of total energy due to elastic deformation and around 7% of energy is absorbed due to tensile failure of fibers and delamination.

When 6 mm thick SiC inserts layered PUF + GFRP laminate is subjected to impact at 240 J, 21% of the total impact energy is absorbed by the compression of ceramic layer. PU foam absorbs 17% of energy in crushing and shear plugging mode. Further, the GFRP laminate absorbs 24% of total energy due to elastic deformation and around 7% of energy is absorbed due to tensile failure of fibers and delamination.

Figure 13 shows the scratches on the impactor during impact on the front facing ceramic layer specimen. This is observed in the impactor when impacted the targets that are layered with SiC plates and inserts.

Force–Time History of Target Material.

A PCB make dynamic load cell of capacity 5 kN was used to capture force–time history of the impact event. Load cell was mounted in the impactor to capture the data during impact when impactor was in contact with target. Figure 14 shows the force–time history of various specimens when the incident energy is 80 J. The maximum peak force is 2.5 kN for GFRP + PUS + GFRP laminate and contact duration is 31 ms. The peak force for PUF + GFRP and PUS + GFRP is same and the contact duration of PUF + GFRP is higher.

Figure 15 shows the force–time history of the specimens subjected to 160 J impact energy. The peak force is 4 kN for GFRP + PUS + GFRP laminate and contact duration is 20 ms which is less when compared to impact at 80 J of energy. The peak force and contact duration are less for other target materials.

Figure 16 shows the force–time history of the target materials subjected to 240 J impact energy. It is observed that sandwiched specimens have higher peak force than the two-layered specimen, and PU sheet offers more resistance and has higher peak force when compared to specimen made of PU Foam.

Figure 17 shows the force–time history of SiC plate and inserts layered target materials subjected to 240 J impact energy. It is observed that the peak force decreases as the energy-absorbing capacity of the specimen decreases. The energy-absorbing capacity decreases as the incident energy increases because of less impact period and less deflection of the specimen when compared to low incident energy.

Materials of various combinations are made to understand their energy-absorbing capability when subjected to impact loading. GFRP laminate is considered as backing material and other layers PU sheet, PU foam, and SiC are layered to protect GFRP from failure. Energy absorption of each layer is discussed and various failure modes of energies are analyzed. Low-velocity impact is conducted by using drop mass setup with mild steel spherical nosed projectiles. The following conclusions are made based on this study:

  • Bonding of PU sheet and PU foam enhances the energy-absorbing capacity of GFRP laminate during impact loading.

  • PU sheet is a better material to absorb impact energy by deformation mode. But PU foam has lesser density than PU sheet.

  • GFRP laminate absorbs maximum energy in deformation of secondary fibers when compared to other failure modes like tensile failure and delamination.

  • Bonding of SiC layer enhances energy absorption capacity during impact by three times.

  • The SiC plate is damaged along with fiber failure and delamination on the composite backing laminate.

  • Failure in the case of inserts is local as only the insert under the impact is damaged and the area around point of impact is intact. The inserts in the target material can be subjected to multiple impacts at different locations.

  • Adelam =

    area of delamination in composite backing

  • di =

    diameter of the impactor

  • E =

    energy absorbed by the laminate

  • El =

    energy lost during impact

  • Esb =

    energy absorbed by composite backing due to shear plugging

  • Edefb =

    energy absorbed by composite backing due to elastic deformation

  • Edelamb =

    energy absorbed by composite backing due to delamination

  • Etfb =

    energy absorbed by composite backing due to tensile failure of fibers

  • Ecc =

    energy absorbed due to compression of ceramic layer

  • Ecp =

    energy absorbed due to core crushing

  • Esp =

    energy absorbed by foam due to shear plugging

  • GIIb =

    mode II fracture toughness of glass/epoxy composite backing

  • KEf =

    kinetic energy of the impactor just after impact

  • KEi =

    kinetic energy of the impactor just before impact

  • M =

    mass of the impactor

  • q =

    crushing strength of the core

  • tb =

    thickness of composite backing

  • tc =

    thickness of ceramic plate

  • tp =

    thickness of core layer

  • Vi =

    velocity of the impactor just before impact

  • Vr =

    residual velocity of the impactor

  • wof =

    maximum transverse deflection

  • x =

    maximum in-plane distance up to which the foam has been crushed

  • εb =

    strain of primary fibers in composite backing

  • εsb =

    strain in elastic limit in composite backing

  • ε0b =

    failure strain of fibers in composite backing

  • εcc =

    compressive failure strain of ceramic

  • σb(εb) =

    stress of primary fibers in composite backing

  • σsb(εsb) =

    equation of stress–strain function curve within elastic limits in composite backing

  • σcc =

    compressive strength of ceramic

  • τp =

    shear plugging strength of core layer

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Signetti, S. , and Pugno, N. M. , 2014, “ Evidence of Optimal Interfaces in Bio-Inspired Ceramic Composite Panels for Superior Ballistic Protection,” J. Eur. Ceram. Soc., 34(11), pp. 2823–2831. [CrossRef]
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Naik, N. K. , Kumar, S. , Ratnaveer, D. , Joshi, M. , and Akella, K. , 2012, “ An Energy-Based Model for Ballistic Impact Analysis of Ceramic-Composite Armors,” Int. J. Damage Mech., 22(2), pp. 1–43.
Lee, M. , and Yoo, Y. H. , 2001, “ Analysis of Ceramic/Metal Armour Systems,” Int. J. Impact Eng., 25(9), pp. 819–829. [CrossRef]
Liu, W. , Chen, Z. , Chen, Z. , Cheng, X. , Wang, Y. , Chen, X. , Liu, J. , Li, B. , and Wang, S. , 2015, “ Influence of Different Back Laminate Layers on Ballistic Performance of Ceramic Composite Armor,” Mater. Des., 87, pp. 421–427.
Qiao, P. , Yang, M. , and Bobaru, F. , 2008, “ Impact Mechanics and High-Energy Absorbing Materials: Review,” J. Aerosp. Eng., 21(4), pp. 235–248. [CrossRef]
Mamalis, A. G. , Robinson, M. , Manolakos, D. E. , Demosthenous, G. A. , Ioannidis, M. B. , and Carruthers, J. , 1997, “ Crashworthy Capability of Composite Material Structures,” Compos. Struct., 37(2), pp. 109–134. [CrossRef]
Mamalis, A. G. , Manolakos, D. E. , Demosthenous, G. A. , and Ioannidis, M. B. , 1998, Crashworthiness of Composite Thin-Walled Structural Components, Technomic Publishing, Lancaster, PA.
Lundberg, P. , Renstro, R. , and Lundberg, B. , 2000, “ Impact of Metallic Projectiles on Ceramic Targets: Transition Between Interface Defeat and Penetration,” Int. J. Impact Eng., 24(3), pp. 259–275. [CrossRef]
Wang, J. , Waas, A. M. , and Wang, H. , 2013, “ Experimental and Numerical Study on the Low-Velocity Impact Behavior of Foam-Core Sandwich Panels,” Compos. Struct., 96, pp. 298–311. [CrossRef]
Zhang, G. , Wang, B. , Ma, L. , Wu, L. , Pan, S. , and Yang, J. , 2014, “ Energy Absorption and Low Velocity Impact Response of Polyurethane Foam Filled Pyramidal Lattice Core Sandwich Panels,” Compos. Struct., 108, pp. 304–310. [CrossRef]
Garcia-Avila, M. , Portanova, M. , and Rabiei, A. , 2014, “ Ballistic Performance of a Composite Metal Foam-Ceramic Armor System,” Procedia Mater. Sci., 4, pp. 151–156. [CrossRef]
Hosur, M. V. , Abdullah, M. , and Jeelani, S. , 2005, “ Manufacturing and Low-Velocity Impact Characterization of Foam Filled 3-D Integrated Core Sandwich Composites With Hybrid Face Sheets,” Compos. Struct., 69(2), pp. 167–181. [CrossRef]
Nemes, J. A. , and Simmonds, K. E. , 1992, “ Low-Velocity Impact Response of Foam-Core Sandwich Composites,” J. Compos. Mater., 26(4), pp. 500–519. [CrossRef]
Gailly, B. A. , and Espinosa, H. D. , 2002, “ Modeling of Failure Mode Transition in Ballistic Penetration With a Continuum Model Describing Micro Cracking and Flow of Pulverized Media,” Int. J. Numer. Methods Eng., 54(3), pp. 365–398. [CrossRef]
Hosseini, M. , and Khalili, S. M. R. , 2013, “ Analytical Prediction of Indentation and Low-Velocity Impact Responses of Fully Backed Composite Sandwich Plates,” J. Solid Mech., 5(3), pp. 278–289.
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References

Zinoviev, P. A. , and Ermakov, Y. N. , 1994, Energy Dissipation in Composite Materials, Technomic Publishing Company, Basel, Switzerland.
Morye, S. S. , Hine, P. J. , Duckett, R. A. , Carr, D. J. , and Ward, I. M. , 2000, “ Modeling of the Energy Absorption by Polymer Composites Upon Ballistic Impact,” Compos. Sci. Technol., 60(14), pp. 2631–2642. [CrossRef]
Abrate, S. , 1997, “ Localized Impact on Sandwich Structures With Laminated Facings,” ASME Appl. Mech. Rev., 50(2), pp. 70–82. [CrossRef]
Wen, H. M. , 2001, “ Penetration and Perforation of Thick FRP Laminates,” Compos. Sci. Technol., 61(8), pp. 1163–1172. [CrossRef]
Balaganesan, G. , Velmurugan, R. , Srinivasan, M. , Gupta, N. K. , and Kanny, K. , 2014, “ Energy Absorption and Ballistic Limit of Nanocomposite Laminates Subjected to Impact Loading,” Int. J. Impact Eng., 74, pp. 57–66. [CrossRef]
Shim, V. P. W. , Tu, Z. H. , and Lim, C. T. , 2000, “ Two-Dimensional Response of Crushable Polyurethane Foam to Low Velocity Impact,” Int. J. Impact Eng., 24(6–7), pp. 703–731. [CrossRef]
Wang, J. , Waas, A. M. , and Wang, H. , 2013, “ Experimental and Numerical Study on the Low-Velocity Impact Behavior of Foam-Core Sandwich Panels,” Compos. Struct., 96, pp. 298–311. [CrossRef]
Bhuiyan, A. , Hosur, M. V. , and Jeelani, S. , 2009, “ Low-Velocity Impact Response of Sandwich Composites With Nanophased Foam Core and Biaxial ±45 Braided Face Sheets,” Composites, Part B, 40(6), pp. 561–571. [CrossRef]
Zaretsky, E. , Asaf, Z. , Ran, E. , and Aizik, F. , 2012, “ Impact Response of High Density Flexible Polyurethane Foam,” Int. J. Impact Eng., 39(1), pp. 1–7. [CrossRef]
Nasirzadeh, R. , and Sabet, A. R. , 2014, “ Study of Foam Density Variations in Composite Sandwich Panels Under High Velocity Impact Loading,” Int. J. Impact Eng., 63, pp. 129–139. [CrossRef]
Karandikar, P. G. , 2009, “ A Review of Ceramics for Armor Applications,” Advances in Ceramic Armor IV, Vol. 29, The American Ceramic Society, Westerville, OH, pp. 163–175.
Bhatnagar, A. , 2006, Lightweight Ballistic Composites: Military and Law-Enforcement Applications, Woodhead Publishing, Cambridge, UK.
Krell, A. , and Strassburger, E. , 2008, “ Hierarchy of Key Influences on the Ballistic Strength of Opaque and Transparent Armor,” Ceram. Eng. Sci. Proc., 28(5), pp. 45–55.
Evci, C. , and Gülgeç, M. , 2013, “ Effective Damage Mechanisms and Performance Evaluation of Ceramic Composite Armors Subjected to Impact Loading,” J. Compos. Mater., 48(26), pp. 3215–3236. [CrossRef]
Krishnan, K. , Sockalingam, S. , Bansal, S. , and Rajan, S. D. , 2010, “ Numerical Simulation of Ceramic Composite Armor Subjected to Ballistic Impact,” Composites, Part B, 41(8), pp. 583–593. [CrossRef]
Signetti, S. , and Pugno, N. M. , 2014, “ Evidence of Optimal Interfaces in Bio-Inspired Ceramic Composite Panels for Superior Ballistic Protection,” J. Eur. Ceram. Soc., 34(11), pp. 2823–2831. [CrossRef]
Benloulo, I. S. C. , and Sanchez-Galvez, V. , 1998, “ A New Analytical Model to Simulate Impact Onto Ceramic/Composite Armors,” Int. J. Impact Eng., 21(6), pp. 461–471. [CrossRef]
Naik, N. K. , Kumar, S. , Ratnaveer, D. , Joshi, M. , and Akella, K. , 2012, “ An Energy-Based Model for Ballistic Impact Analysis of Ceramic-Composite Armors,” Int. J. Damage Mech., 22(2), pp. 1–43.
Lee, M. , and Yoo, Y. H. , 2001, “ Analysis of Ceramic/Metal Armour Systems,” Int. J. Impact Eng., 25(9), pp. 819–829. [CrossRef]
Liu, W. , Chen, Z. , Chen, Z. , Cheng, X. , Wang, Y. , Chen, X. , Liu, J. , Li, B. , and Wang, S. , 2015, “ Influence of Different Back Laminate Layers on Ballistic Performance of Ceramic Composite Armor,” Mater. Des., 87, pp. 421–427.
Qiao, P. , Yang, M. , and Bobaru, F. , 2008, “ Impact Mechanics and High-Energy Absorbing Materials: Review,” J. Aerosp. Eng., 21(4), pp. 235–248. [CrossRef]
Mamalis, A. G. , Robinson, M. , Manolakos, D. E. , Demosthenous, G. A. , Ioannidis, M. B. , and Carruthers, J. , 1997, “ Crashworthy Capability of Composite Material Structures,” Compos. Struct., 37(2), pp. 109–134. [CrossRef]
Mamalis, A. G. , Manolakos, D. E. , Demosthenous, G. A. , and Ioannidis, M. B. , 1998, Crashworthiness of Composite Thin-Walled Structural Components, Technomic Publishing, Lancaster, PA.
Lundberg, P. , Renstro, R. , and Lundberg, B. , 2000, “ Impact of Metallic Projectiles on Ceramic Targets: Transition Between Interface Defeat and Penetration,” Int. J. Impact Eng., 24(3), pp. 259–275. [CrossRef]
Wang, J. , Waas, A. M. , and Wang, H. , 2013, “ Experimental and Numerical Study on the Low-Velocity Impact Behavior of Foam-Core Sandwich Panels,” Compos. Struct., 96, pp. 298–311. [CrossRef]
Zhang, G. , Wang, B. , Ma, L. , Wu, L. , Pan, S. , and Yang, J. , 2014, “ Energy Absorption and Low Velocity Impact Response of Polyurethane Foam Filled Pyramidal Lattice Core Sandwich Panels,” Compos. Struct., 108, pp. 304–310. [CrossRef]
Garcia-Avila, M. , Portanova, M. , and Rabiei, A. , 2014, “ Ballistic Performance of a Composite Metal Foam-Ceramic Armor System,” Procedia Mater. Sci., 4, pp. 151–156. [CrossRef]
Hosur, M. V. , Abdullah, M. , and Jeelani, S. , 2005, “ Manufacturing and Low-Velocity Impact Characterization of Foam Filled 3-D Integrated Core Sandwich Composites With Hybrid Face Sheets,” Compos. Struct., 69(2), pp. 167–181. [CrossRef]
Nemes, J. A. , and Simmonds, K. E. , 1992, “ Low-Velocity Impact Response of Foam-Core Sandwich Composites,” J. Compos. Mater., 26(4), pp. 500–519. [CrossRef]
Gailly, B. A. , and Espinosa, H. D. , 2002, “ Modeling of Failure Mode Transition in Ballistic Penetration With a Continuum Model Describing Micro Cracking and Flow of Pulverized Media,” Int. J. Numer. Methods Eng., 54(3), pp. 365–398. [CrossRef]
Hosseini, M. , and Khalili, S. M. R. , 2013, “ Analytical Prediction of Indentation and Low-Velocity Impact Responses of Fully Backed Composite Sandwich Plates,” J. Solid Mech., 5(3), pp. 278–289.

Figures

Grahic Jump Location
Fig. 1

Target laminates: (a) PUF + GFRP, (b) PUS + GFRP, (c) GFRP + PUF + GFRP, and (d) GFRP + PUS + GFRP

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Fig. 2

(a) Target laminates with SiC plate and (b) target laminate with SiC inserts

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Fig. 3

Drop weight impact test setup, fixture, and specimen

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Fig. 4

Side view of crushing of core material

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Fig. 5

GFRP + PUF + GFRP laminate impacted at 160 J of incident energy

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Fig. 6

GFRP + PUS + GFRP laminate impacted at 160 J of incident energy

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Fig. 7

GFRP + PUF + GFRP laminate impacted at 240 J of incident energy

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Fig. 8

GFRP + PUS + FRP laminate impacted at 240 J of incident energy

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Fig. 9

Energy absorbed PUS + FRP laminate impacted at 80 J of incident energy

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Fig. 10

Impact on 6 mm thick front facing SiC plate layered PUF + GFRP laminate at incident energy of 240 J

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Fig. 11

The front, side, and rear views of 10 mm thickness SiC plate layered PUF + GFRP

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Fig. 12

Impact on 6 mm thick front facing SiC inserts layer at incident energy of 240 J

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Fig. 13

Scratches on the impactor due to ceramic layer

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Fig. 14

Force–time history of target material when the incident energy is 80 J

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Fig. 15

Force–time history of target material when the incident energy is 160 J

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Fig. 16

Force–time history of target material when the incident energy is 240 J

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Fig. 17

Force–time history of SiC layered target material when the incident energy is 240 J

Tables

Table Grahic Jump Location
Table 1 Energy absorbed by the target materials for 80 J and 160 J of impactor energy
Table Grahic Jump Location
Table 2 Energy absorbed by the target materials for 240 J of impactor energy
Table Grahic Jump Location
Table 3 Energy absorbed by target with SiC layered PUF + GFRP laminate in various failure modes at impact energy of 240 J

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