Aramid Laminates Research Articles

Effect of thermo-oxidative ageing on changes of physical-mechanical parameters of aramid and UHMWPE laminates

Abstract This work is focused on monitoring of the effect of thermo-oxidative ageing of laminates on their physical-mechanical parameters, such as tensile strength, tensile modulus of elasticity, flexural strength, flexural modulus of elasticity and hardness. Changes of mentioned parameters were observed on two types of laminates based on aramid and two types based on UHMWPE (Ultra High Molecular Weight Polyethylene). The laminates were exposed to the accelerated thermo-oxidative ageing under higher temperature in the presence of atmospheric oxygen. The aim of the work was to find the physical-mechanical parameter with the greatest changes caused by thermo-oxidative ageing. This parameter was consequently chosen for the prediction of laminates lifetime. From the obtained results, it can be seen that aramid laminates show a significantly higher temperature resistance compared to UHWPE-based laminates.

Synergistic Effects of Impact and Attack Angles on Anti-Penetration Performances of Thin Aramid Laminates

Synergistic Effects of Impact and Attack Angles on Anti-Penetration Performances of Thin Aramid Laminates

Ballistic perforation of aramid laminates: Projectile nose shape sensitivity

The influence of projectile shape on the ballistic properties and mechanism of aramid laminates is investigated through experiments and simulations. Three types of projectiles (blunt, hemispherical, and ogival) are used to obtain ballistic curves. The dynamic penetration process, deformation and damage characteristics of the targets are analyzed. A three-dimensional finite element model is established, and good agreement is observed between the simulation and test results. The findings demonstrate that projectile shape significantly impacts the ballistic response of aramid laminates. As the projectile transitions from blunt and hemispherical to ogival, the ballistic limiting velocity decreases continuously, the area of target plate deformation and damage decreases, and the occurrence of delamination becomes less pronounced. And the energy dissipation through local damage, elastic deformation and overall motion of the aramid material is decreasing and the energy dissipation through friction is increasing.

Numerical Simulation of Anti-penetration Performance of Ceramic/Aramid Fiber/PE-UHMW Composite Armor

In order to study the anti-penetration performance of ceramic/aramid fiber/PE-UHMW composite armor, based on the FEM-SPH coupling algorithm, SPH model is established for brittle ceramic materials to simulate the formation of ceramic cone, crack propagation and fragmentation splash process. The failure mode on aramid fiber and PE-UHMW is analyzed. The influence of different projectile velocities and impact points on the anti-penetration performance of the composite armor are analyzed. The results show that the ceramic panel in the composite armor absorbs part of the kinetic energy of the projectile through passivation, fragmentation of the projectile and panel fragmentation. The failure modes of aramid laminates are mainly delamination shear failure, bending deformation and fiber tensile fracture. The failure modes of PE-UHMW laminates are mainly compression shear failure of the projectile facing surface and small-scale delamination tensile failure of the back layer fiber. When the projectile velocity is less than the ballistic limit, the energy absorption of composite armor and the maximum deformation of back plate increase with the increase of projectile velocity. When the projectile velocity is greater than the ballistic limit, the energy absorption rate of composite armor begins to decrease. When the impact point of the projectile is located at the edge of the ceramic block, the ceramic can’t effectively consume the kinetic energy of the projectile, and the composite armor presents bad performance.

Shattering Effect Study of Aramid–Steel Composite Target Plates under Localized Blast Loading

With the extensive application of composite laminates in protective structures, new materials and new structures have been developed rapidly. As an excellent impact-resistant material, aramid fiber is widely used in the field of protective structures. Aramid laminates show excellent performance in anti-penetration, but there is no research on its anti-explosive characteristics. In this paper, a kind of aramid–steel composite target (ASCT) plate protective structure is proposed innovatively. The failure mode and damage mechanism of three kinds of ASCT plates with equal area density and single-layer steel plates under a local explosion load are studied, and the most effective composite mode is given. The results show that the aramid laminates stuck on the back explosion surface ASCT (SA) exhibit the best anti-explosion effect, which is center deflection reduced by 12% and 18% compared with a single-layer steel plate (S-1) and an equal-thickness steel plate (S-2), respectively. Plate ASCT (SA), plate ASCT (AS), and ASCT (SAS) plate center tear failure did not occur. The analysis shows that different combinations change the propagation of stress waves in the structure, which in turn affects the failure of the composite plate. The critical failure dose of different structural configuration plates is obtained by simulation. The influence of explosion center distance, explosive charge, and bonding thickness of aramid laminate on the central deflection of steel plate was discussed by dimensional analysis, and the empirical formula of central deflection of the aramid–steel composite target plate was obtained. The research results can provide a theoretical basis and reference for the lightweight and efficient protection of composite structural armor.

Castor Oil-Based Polyurethane/S2 Glass/Aramid Hybrid Composites Manufactured by Vacuum Infusion.

This study evaluates the hybridization effect of S2-glass/aramid on polyurethane (PU) composites produced by vacuum infusion. Different laminates were produced with similar thickness (around 2.5 mm), using, as reinforcement, only aramid fabrics (five layers, named as K5) or only S2-glass fabrics (eight layers, named as G8). Furthermore, hybridization was obtained by manufacturing symmetrical hybrid inter-ply laminates, with four S2-glass layers and two of aramid, (G2K)S and (KG2)S. The mechanical response of the laminates was evaluated in tensile, interlaminar shear strength, dynamical mechanical analysis and quasi-static indentation tests, and related to their morphological characteristics. The main results show that the pure glass composites presented less voids, but a higher density as well as higher tensile stiffness and strength. The aramid laminates showed a high capability for absorbing impact energy (ca. 30% higher than the pure glass laminates), and the hybrid laminates had intermediate properties. More importantly, this work shows the possibility of using a polyurethane matrix for vacuum infusion processing, effective even for aramid/S2-glass hybrid composites with thermoset polyurethane resin. This study is therefore promising for impact absorption in applications such as protective armor. The studied hybrid laminate may display a suitable set of properties and greater energy absorption capability and penetration resistance for impact applications.

The Effects of Hybridisation of Composites Consisting of Aramid, Carbon, and Hemp Fibres in a Quasi-Static Penetration Test.

The quasi-static penetration properties of hybrid laminates were experimentally investigated. Aramid fabrics, carbon fabrics, and short hemp fibres were applied as the reinforcements of hybrid and non-hybrid composite laminates with polyurethane–polyurea (PUR/PUA) matrix. The laminates were made by hand, in a mould. They were cured at room temperature for 24 h. Hybrid laminates consisted of aramid and carbon layers in two different configurations, i.e., aramid at the innermost layers and outermost layers. Aramid/PUR/PUA and carbon/PUR/PUA composites were fabricated for comparison purposes. Laminates were also prepared via an analogue sequence of laying the reinforcement layers with the addition of 5% by weight of hemp fibres in the PUR/PUA matrix. Quasi-static penetration tests (QSPT) were conducted using a tensile testing machine with a surface-hardened, hemispherical, steel punch (9 mm diameter tip), reflecting the geometry of the Parabellum projectile. A quasi-static puncture test was carried out until the laminate was perforated. The ratio between the support span (Ds) and the punch diameter (Dp) was SPR = Ds/Dp = 5.0. The results showed the influences of laminate hybridisation on the values of absorbed energy, punch shear strength, and damage mechanism in the QSPT test. The addition of hemp fibres to aramid laminates resulted in a positive hybridisation effect. The order of layers of aramid and carbon fabrics in hybrid laminates influenced the results obtained in the QSPT test.

Experimental analysis of puncture resistance of aramid laminates on styrene-butadiene-styrene and epoxy resin matrix for ballistic applications

The work aimed to evaluate the influence of the type of matrix and the number of reinforcement layers on the puncture of aramid laminates. The samples were examined under laboratory conditions and in ballistic tests. Two series of aramid laminates were produced with different types of the polymer matrix. The epoxy resin (EP) and the styrene-butadiene-styrene (SBS) copolymer were used as the matrix. For comparison, a puncture test was performed for the fabric with the same number of layers in contrast to the laminates. Laboratory tests were carried out using the InstronDynatup 9250 HV drop hammer. The results obtained during the laboratory and ballistic examinations were compared. The samples were fired with a 9×19mm Parabellum projectile. Research into the low-velocity range have shown that SBS laminates absorb impact energy more effectively than epoxy resin ones, but they are similar to fabrics without a polymer matrix. The results of ballistic tests are divergent and indicate that unbound materials are more efficient at absorbing energy than laminates. The reason for this is the different damage mechanisms.

Experimental analysis for stabbing resistance of different aramid composite architectures

Stab resistance is a crucial material property in the case of fabrics used in personal protection equipment due to the extensive occurrence of this threat. Personal Protection Equipments (PPE) are commonly based on woven aramids, where the stacking sequence is critical to improve the ratio between protection and weight. PPE should combine optimal penetration resistance with ergonomic requirements. This paper focuses on experimental characterisation of the stab protective efficiency of different architectures of aramid laminates. The influence of different stacking sequences, based on the combination of not treated (N) and thermoplastic aramids (TP), is analysed showing a significant influence of this factor. In the range of the impact energies analysed in this work, it can be concluded that the TP-N-TP sequence is the best choice for stabbing protection.

Ballistic Efficiency of Multilayered Armor Systems with Sisal Fiber Polyester Composites

The urban violence and the different types of global armed conflicts demand efficient protective systems against high energy ammunition. Multilayered Armor Systems (MAS) provide efficient protection by making use of lighter and more efficient materials. A typical MAS may be composed of three layers: a front ceramic followed by a composite, backed by a ductile metal. Polymer composites reinforced with natural fibers have proven to be effective second layers, being also lighter, low-cost and environmentally friendly as compared to conventional composites like KevlarTM. The present work evaluates MAS using as second layer polyester composites reinforced with 10, 20, and 30 vol. % of sisal fibers. Ballistic tests were performed using class III 7.62x51 mm ammunition, based on the NIJ 0101.06 backface signature methodology. Both the 30 vol.% sisal fiber composite and the conventional aramid laminates were equally efficient in terms of MAS second layer. The explanation might be the similar capacity of the different composites to retain the fragments generated by the interaction of the projectile with the front ceramic, independently of the percentage of sisal fibers.

High energy ballistic and fracture comparison between multilayered armor systems using non-woven curaua fabric composites and aramid laminates

For personal protection against high kinetic energy projectiles, multilayered armor systems (MAS) are usually the best option. They combine synergistically the properties of different materials such as ceramics, composites and metals. In the present work, ballistic tests were performed to evaluate multilayered armor systems (MAS) using curaua non-woven fabric epoxy composites as second layer. A comparison to a MAS using aramid (Kevlar™) fabric laminates was made. The results showed that the curaua non-woven fabric composites are suitable to the high ballistic applications, and are promising substitutes for aramid fabric laminates.

Effect of different construction designs of aramid fabric on the ballistic performances

Current construction methods for soft armour products involve woven and cross-ply laminates. Both methods claim to offer high-energy absorption capability towards projectile impact. Currently, there are less specific data comparing both construction methods. In the cross-ply manufacturing process, the fibers are aligned in one direction, spread into a web and adhered with a resin. Two fiber resin sheets are layered (one in a 0° direction and another in a 90° direction) and fused. Therefore, this study attempted to investigate the effects of different textile designs of aramid fabrics on the ballistic performance, specifically on the energy dissipation and projectile arrest for soft body armour at a 390ms−1 projectile velocity. It was found that the cross-ply laminated aramid construction exhibited better ballistic performance in terms of higher energy dissipation and minimum layer of projectile arrest upon impact. In five layers of fabric, it was clearly shown that the cross-ply aramid laminates could dissipate the impact energy up to 17% compared to those of the woven aramid (i.e. 5%). At the same level of NIJ standard, the cross-ply aramid laminates have the capability to stop the projectile at the minimum layer of the first ply and the maximum layer of seventh. Meanwhile, for woven aramid, the ability to arrest the bullet was at the minimum layer of sixth ply and the maximum layer of 15th ply. It has been demonstrated that the cross-ply structure can dissipate the energy by threefold compared to the woven structure.

The Study of Obliquity on the Ballistic Performance of Basket Fabric Composite Materials

The main purpose of this study is to investigate the ballistic resistance behavior of basket 2 × 2 fabric aramid laminate composite materials experiencing oblique impact. The ballistic resistance performance at normal impact is discussed widely in most reports. However, the reports concerning ballistic resistance behavior at oblique impact are limited in metal material. The research of the oblique ballistic behavior of fabrics composites is rarely to be seen. The ballistic results show that the degree of ricochet of aramid laminates is greater than metal (>75° or even more). The offset direction when a projectile perforates the laminate is converse with those of metal plates. Both sliding and embedding behaviors were found in the laminate after impact. So, the possibility that a basket weave causes a ricochet will be less than that of a plain weave.

The fatigue behavior and delamination properties in fiber reinforced aramid laminates

The fuselage-wing intersection suffers from the cyclic bending moment of variable amplitude. Therefore, the influence of cyclic bending moment on the delamination and the fatigue crack propagation behavior in AFRP/ AI laminate of fuselage-wing was investigated in this study. The cyclic bending moment fatigue test in AFRP/ AI laminate was performed with five levels of bending moment. The shape and size of the delamination zone formed along the fatigue crack between aluminum sheet and aramid fiber-adhesive layer were measured by an ultrasonic C-scan. The relationships between da/dN and △K, between the cyclic bending moment and the delamination zone size, and between the fiber bridging behavior and the delamination zone were studied. As results, fiber failures were not observed in the delamination zone in this study; the fiber bridging modification factor increases and the fatigue crack growth rate decrease; and the shape of delamination zone is semi-elliptic with the contour decreasing non-linearly toward the crack tip.

The Mechanical Properties of Particulate-filled Aramid and Polyethylene Laminates

Some mechanical properties of particulate-filled polyethylene/epoxy and aramid/epoxy laminates are reported, following earlier work with particulate-filled glass/epoxy laminates. The behaviour of the organic fibre laminates was different from that of glass fibre ones, investigated and reported earlier. There was an increase in compression strength with increasing filler content, with both kinds of organic fibre reinforcement. The interlaminar shear strength values were significantly lower for the polyethylene laminates than the aramid ones at all filler concentrations, and they fell to little more than 10MPa at high filler levels. However, the impact damage zone in drop weight tests was generally smaller for the polyethylene laminates, and the visible crack damage was less apparent than in the aramid ones. The flexural strength and modulus values are also reported. © of SCI.

The Mechanical Properties of Particulatefilled Aramid and Polyethylene Laminates

The Mechanical Properties of Particulatefilled Aramid and Polyethylene Laminates

An investigation into the drilling of ballistic Kevlar composites

Abstract In this investigation the problems associated with drilling aramid laminates are outlined and an assessment is made of previous work. A suitable tool was developed from analysis of the cutting action and a number of experiments were carried out to assess the effect of geometry variation on the performance of the proposed tool shape. Comparative tests were conducted with commercially available tools.

Flexural fatigue of marine laminates reinforced with woven roving of E‐glass and of Kevlar® 49 aramid

AbstractA comparison of the flexural fatigue characteristics of E‐glass and Kevlar® 49 aramid in polyester and vinyl ester resin hand lay‐ups typical of boat hull laminates is presented. Data on unidirectional E‐glass and aramid composites from epoxy preimpregnated tapes are reported for comparison. The data indicate that while the initial flexural strength of E‐glass woven roving laminates is greater than that of aramid laminates, the runout stress of aramid laminates at 106 fatigue cycles is similar or superior to glass. S‐N curves for aramid laminates are flatter indicating better flexural fatigue resistance.