Current study reported a facile method to investigate the effects of stacking sequence layers of hybrid composite materials on ballistic energy absorption by running the ballistic test at the high velocity ballistic impact conditions. The velocity and absorbed energy were accordingly calculated as well. The specimens were fabricated from Kevlar, carbon, and glass woven fabrics and resin and were experimentally investigated under impact conditions. All the specimens possessed equal mass, shape, and density; nevertheless, the layers were ordered in different stacking sequence. After running the ballistic test at the same conditions, the final velocities of the cylindrical AISI 4340 Steel pellet showed how much energy was absorbed by the samples. The energy absorption of each sample through the ballistic impact was calculated; accordingly, the proper ballistic impact resistance materials could be found by conducting the test. This paper can be further studied in order to characterise the material properties for the different layers.
During the life of a structure, impacts by foreign objects could be expected to occur during manufacturing, service, and maintenance operations. An example of in-service impact occurs during aircraft takeoffs and landings when stones and other small debris from the runway were propelled at high velocities by the tires. During the manufacturing process or during maintenance, tools could be dropped on the structure. In this case, impact velocities are small but the mass of the projectile is larger. Laminated composite structures are more susceptible to impact damage than a similar metallic structure. In composite structures, impacts create internal damage that often cannot be detected by visual inspection. This internal damage can cause severe reductions in strength and can grow under load. Therefore, the effects of foreign object impacts on composite structures must be understood, and proper measures should be taken in the design process to account for these expected events. Concerns about the effect of impacts on the performance of composite structures have been a factor in limiting the use of composite materials. For these reasons, the problem of impact has received considerable attention in developing not only technical know-how but also a practical and analytical approach to problem solving that can allow addressing a range of aerospace engineering challenges. This was particularly true under high velocity ballistic impact scenarios [
The body of aircrafts is susceptible to accidental damages from low- to high-energy impacts of such hazards as dropped tools during maintenance, runway debris, hailstones, and sandstorm. These impacts could bring about considerable strength reduction, and the localized damage was potentially a source of mechanical weakness, particularly under the mechanical applications [
Furthermore, the damage consequent upon a minor impact can grow to large size under the mechanical applications. The nature of the impact damage in hybrid composite laminates ranges from surface damage and subsurface damage to complete penetration, depending upon the impact loading conditions. Generally, under the ballistic impact, impact loading on composite laminates can cause surface or internal damage in the form, including fibre breakage, delamination, and matrix cracking. Such damages can reduce laminate tensile strength, resulting in so-called part through the thickness damage. This sort of damage is of a complicated form, consisting of fluctuating amounts of matrix cracks, fibre cracks, and delamination. The complexity of the damage makes it difficult to assess the precise mechanisms controlling strength reduction. Among these modes of impact damage, delamination has the most detrimental effects on laminate stiffness and strength and has received a considerable amount of attention [
Sultan et al. [
Three types of fibres, including glass, carbon, and Kevlar, were used in fabricating the specimens. The Kevlar fabric used in all composite target constructions was plain-woven Hexcel Aramid (polyparaphenylene terephthalamide), high-performance fabric Style 706 (Kevlar KM-2, 600 denier) with a real density of 180 g/m2. Room temperature curing and the ratios of 50 parts epoxy resin (EPOKUKDO YD-128) to 50 hardeners (Polyamide-Domide (A.V: 350)) by weight were comprehensively cured after seven days at 20°C [
Table
Fabricated composite plates were divided into five groups (from top surface to bottom surface) [
HYBRID 1 | HYBRID 2 | HYBRID 3 | HYBRID 4 | HYBRID 5 |
---|---|---|---|---|
Kevlar | Glass | Kevlar | Glass | Kevlar |
Carbon | Carbon | Glass | Kevlar | Carbon |
Glass | Kevlar | Carbon | Carbon | Glass |
Kevlar | Carbon | Glass | Carbon | Glass |
Glass | Kevlar | Carbon | Glass | Carbon |
Carbon | Glass | Kevlar | Kevlar | Kevlar |
The specimens were produced by hand lay-up method. The experimental setup was according to guidelines given in the NIJ Standard 0108.01 [
Ballistic test setup according to NIJ Standard 0108.01 [
(a) Gun equipment [
Gas gun tunnel for conducting the ballistic impact test [
Figure
Schematic of the cylindrical AISI 4340 Steel pellet [
This invention relates to high-speed cameras and in particular to high-speed cameras having resolution times of less than one-tenth microsecond. High frame rates required a sensor with good sensitivity, either a very good shuttering system or a very fast strobe light, and also require some means of capturing successive frames, either with a mechanical device or by moving data off electronic sensors very quickly. In such higher frame rates, it is found that a slight difference in debris cloud formation was captured in the interframe of 4 microseconds, which is equivalent to the 250,000 frames per second, and the debris fragment distributions appear to be slightly narrower and thinner at cryogenic temperature.
It is an established fact that absorbed energy by a specimen in ballistic test is means to quantify impact-penetration resistance. Therefore, the absorbed kinetic energy of armor-projectile interaction can be linked by equation for determining kinetic energy.
After fabricating the required number of specimens, a variety of tests were carried out to investigate the behaviour of the various groups of specimens when they were subjected to impact and then under compression. Moreover, the number of experimental runs is fifty.
Figure
Process of penetration of pellet into the specimens [
Comparison of the specimens’ weight losses’ percentages after ballistic impact.
Figure
Postimpact images of damaged specimens’ profiles. (a) Impact-induced damage profile viewed from the front face and (b) impact-induced damage profile viewed from the back face.
The perimeter of the impacted zones.
Figure
Comparing the amount of energy absorption in the specimens of 182 m/s as the initial velocity.
Table
Final velocity and energy absorption of the specimens.
Specimen | Final velocity (m/s) | Ballistic energy absorption (J) |
---|---|---|
Hybrid 1 | 14.36 | 94.36 |
Hybrid 2 | 4.47 | 95.17 |
Hybrid 3 | 8.76 | 95.01 |
Hybrid 4 | 5.28 | 95.15 |
Hybrid 5 | 8.21 | 95.04 |
Carbon | 26.87 | 93.16 |
Figure
Comparison of the energy absorption and different final velocities of six specimens at 182 m/s as the initial velocity.
Figure
Figure
Percentage change of the COR.
The results show, first, that Hybrid 2 has the superlative energy absorption of 95.17 J. Second, it can be concluded that stacking the first layer with glass fibre is better than to use the Kevlar fibre, according to Hybrid 2 and Hybrid 4 impact specimens with ballistic impact energy absorption of 95.17 J and 95.15 J, respectively. Moreover, the results indicated that using the combination of carbon and glass is more efficient to in the central layers. Third, in accordance with Hybrid 1 with ballistic impact energy absorption of 94.36 J, using the carbon fibre is not recommended at the last layer.
The authors declare that there is no conflict of interests regarding the publication of this paper.