Polyethylene Laminates Research Articles

Analyzing the back-face deformation of curved UHMWPE composite laminate under high-speed impact

Ballistic protection extensively employs curved ultra-high-molecular-weight polyethylene (UHMWPE) laminates to conform to protective targets. However, ballistic tests have indicated that the curvature of laminates increases back-face deformation, diminishing ballistic performance, while the mechanism behind this curvature effect on back-face deformation remains unclear. In this paper, the back-face deformation of curved UHMWPE laminates, including apex displacement and the boundary of the deformation region, are systematically studied through numerical simulation and theoretical analysis. Firstly, a numerical model of curved UHMWPE laminates under the high-speed impact is established. The numerical results indicate that as the curvature increases, the deformation region becomes more concentrated, resulting in a larger apex displacement. Secondly, as the curvature increases from zero, the deformation mode of curved laminates changes from membrane stretching dominated to a combination of membrane stretching and bending. Finally, considering the change in the deformation mode, a theoretical analysis for the propagation of bending waves in an orthotropic curved plate is conducted to reveal the relationship between curvature and back-face deformation. The theoretical analysis shows that increasing curvature slows bending wave speed, reducing in-plane deformation region movement, thus increasing apex displacement. This study is expected to help design curved UHMWPE laminates with better ballistic performance.

Ballistic impact wave and bulge profile propagation characteristics and blunt injury assessment of UHMWPE laminate composite

Amid escalating localized conflicts worldwide, the elucidation of the mechanisms and quantification blunt trauma the emergency services and military personnel confronted becomes imperatively. However, the understanding of bullet-induced bulge formation on the laminate's back face, impact wave propagation, and consequent trauma assessment methods remains incomplete. This study applies 3-dimension digital image correlation (3D-DIC) method to reveals these phenomena by utilizing a lead-core bullet traveling at 334.93 m/s to impact an ultra-high molecular weight polyethylene (UHMWPE) laminate. The results show that the initial transverse propagation velocity of bulge profile is 24.79% smaller than the theoretical calculation, which indicates the reduction caused by cohesive matrix. The transverse wave demonstrates a double exponential attenuation pattern, which could be decomposed into two single exponential attenuation curves. The bulge profile shows hyperbolic pattern, which reveals the stability of the bulge shape and the temporal evolution pattern. Increasing the laminate-body gap leads to a decline in Blunt Criterion (BC) and the Abbreviated Injury Scale (AIS) values reduce from 2 to 0 correspondingly. The numerical model confirms the compression wave velocity as 1447.77 ± 123.10 m/s in the thickness direction and 9542.86 ± 3087.75 m/s in the fiber direction. These findings reveals and quantified the propagation patterns of back bulge and compressive wave, and thus could provide data-driven insights to improve body armor performance and blunt trauma assessment for individual soldiers.

Ballistic performance and energy transfer of ultrahigh molecular weight polyethylene laminate

Soldier protection is crucial in contemporary localized conflicts, However, the impact response mechanism of UHMWPE laminate as the insert plate of ballistic helmet and bulletproof vest is still unclear. This study utilized 3D-DIC technology to analyze the impact response of UHMWPE laminates subjected to a 9 mm lead-core pistol bullet at a velocity of 334.93 m/s. The damage mode and response characteristics of the back surface were revealed; an effective numerical calculation method was established and could reveal the energy conversion process. The bullet penetrated the front face with 1.01 mm, resulting in a cross-shaped failure feature due to fiber bundle compression and aggregation. The numerical model confirmed its accuracy by comparing the height, width, and inplane strain distribution within the inplane of the bulge with experimental results. It further investigated the interaction between the bullet and the laminate, and energy transformation. The bullet's kinetic energy decreased by 80.64 %, in which the laminate absorbs 30.84 % of the bullet's energy as internal energy and 35.06 % as kinetic energy, meanwhile the bullet's internal energy increases by 11.77 %. The results show the damage mode and energy transformation of laminate, which provides theoretical support for revealing the impact response mechanism and improving the protective energy absorption efficiency.

Experimental study on the synergetic damage of sandwich panel with armored hybrid core under combined blast and fragment loading

Synergetic damage under combined blast and fragment loading drives innovational design of protective structures. In present study, sandwich panel with armored hybrid core was designed, fabricated and finally tested under combined blast and fragment loading. The failure behaviors and the underlying mechanisms were analyzed for the components of sandwich panel. The sandwich panel displayed superior performance over equivalent solid plate. The designability of special interest was exploited by elaborating the effects of face sheet configuration, core material and core sequence on the failure behaviors. Experimental results demonstrate that the same thickness of the front and back faces is beneficial for the constraint of back face deflection. The aluminum foam and ultra-high molecular weight polyethylene (UHMWPE) laminate, adopted as the components of armored hybrid core, cooperated well against combined blast and fragment loading by suffering crushing erosion failure and global bulge deformation, respectively. The potential of armored hybrid core is strongly associated with the core sequence. The ceramic layer supported by the material with high stiffness and the protection of upper bulletproof material for UHMWPE laminate layer would benefit the performance of whole panel. The optimal design of core sequence could markedly reduce back face deflection and even avoid the petalling failure of back face.

Study on the resistance of UHMWPE laminates against oblique penetration of projectiles

AbstractTo solve the problem of the wall panel of high‐performance shelters protecting against the oblique penetration of projectiles, ballistic experiments were carried out with ultra‐high molecular weight polyethylene (UHMWPE) laminates subjected to normal penetration by high‐velocity projectiles, and the deformation and failure characteristics of UHMWPE laminates were analyzed. The numerical model of the resistance of UHMWPE laminates against penetration of projectiles was established by using the finite element program LS‐DYNA. The validity of the numerical model was verified by the experimental results of damage morphology and the depth of depression of the target plate and the deformation of the warhead. On this basis, the ricochet angle and failure mode of the UHMWPE target plate against projectile penetration were studied numerically, and the impact of the angle of incidence on the residual kinetic energy and normal penetration displacement of the bullet, as well as the damage morphology of the UHMWPE target plate, was revealed by using simulation. The results showed that the ricochet angle of the bullet obliquely penetrating into the UHMWPE target plate was in the range of 45° to 50°; at the initial stage of projectile penetration, the shear fracture failure of the fiber layer mainly occurred at the striking face of the UHMWPE target plate. Under the impact of the warhead deformation, with the reduction of the residual velocity of the bullet, the failure mode gradually changed to the tensile and interlaminar cohesion failure of the fiber layer near the back face; When the angle of incidence was greater than the ricochet angle, the residual kinetic energy of the projectile increased slowly with the increase of the angle of incidence of the bullet and then went up approximately linearly; the normal displacement of the bullet obliquely penetrating into the UHMWPE target plate decreased slowly after reaching the peak, and the peak value of the normal penetration displacement decreased gradually with the increase of the angle of incidence, and the time to peak of the displacement shortened gradually. The damage area of the bulge on the back surface of the UHMWPE target plate after penetration decreased gradually with the increase of the angle of incidence. The research results can provide a theoretical reference for the application of UHMWPE laminates in the design of military bulletproof shelters and armor.

Tensile Properties Characterisation of Hybrid Luffa/GCW Fiber Reinforced Polymer Composite

Extensive research has been conducted on fiber reinforced polymer (FRP) composites, which have demonstrated superior mechanical properties compared to their individual components. In order to add on to current research trends, the use of ground coffee waste (GCW) and Luffa fibers reinforced polyethylene (PE) composites were fabricated to produce a hybrid natural FRP composite. Tensile testing of the composite indicates that the optimum fiber volume to be between 15% and 35%, as the tensile strength exhibited 9.32 MPa and 8.75 MPa, respectively. Similarly, the tensile modulus of the fabricated composite peaked at 25% with 238 MPa, then declined to 173 MPa at 35%. This indicates that the fibers effectively reinforce the polymer matrix, but once the composite reaches its optimal fiber volume, a decrease in both tensile strength and tensile modulus is observed. The reduction in tensile properties can be attributed to an uneven distribution of load-bearing capacity throughout the composite, as the fibers are no longer able to fully support the matrix once the optimal fiber volume is reached. The specific tensile strength and specific tensile modulus also shows that with the inclusion of Luffa fiber and GCW microfiber contributed to a lighter weight composite. In a nutshell, the hybrid composite fabricated using 25% fiber volume exhibited a tensile strength almost similar to its neat matrix counterpart, though has a noteworthy value in terms of its tensile modulus. The hybrid composite can be as strong in terms of tensile strength, but far more significant in its rigidity, in comparison to the neat polyethylene laminate. Therefore, it showed that the hybrid natural Luffa/GCW FRP has the potential in the engineering industry, such as lightweight furniture, household appliances, automotive parts, and other composite engineering applications.

An experimental study of the penetration resistance of UHMWPE laminates with limited thickness

Ultra-high molecular weight polyethylene (UHMWPE) laminates represent the most weight-efficient industrial fiber-reinforced resin-based composite material for ballistic protection. To comprehensively understand the anti-penetration mechanism and quantify the anti-penetration performance of UHMWPE laminates, theoretical, experimental, and equation-fitting methods are employed to study and test the ballistic response characteristics of UHMWPE laminates. The results reveal that UHMWPE fibers possess a theoretically determined longitudinal wave velocity that exceeds 10 km/s and exhibit an extremely strong stress diffusion capacity. The anti-penetration mechanism and performance of UHMWPE laminates are significantly influenced by the laminate thicknesses, projectile velocities, and temperatures. As the laminate thickness increases, the ballistic limits of UHMWPE laminates increase almost linearly. Large area delamination and back face deformation play a crucial role in the energy dissipation of UHMWPE laminates. With the increase of projectile velocities, there exists an energy limit representing the maximum energy absorption capacity of the UHMWPE laminates that is worthy of reasonable utilization in spacing ballistic-proof armors. Additionally, the ballistic performance of UHMWPE laminates generally decreases with increasing temperatures, and this trend becomes more pronounced after 80 ℃. Based on data-driven analysis, this paper proposes an equation for calculating the ballistic limit of UHMWPE laminates that takes into account the temperatures and projectile shapes, with a prediction error basically within 5 %. The research results can offer valuable guidance for the ballistic-proof design of UHMWPE laminates.

Numerical and theoretical modeling of the elastic-plastic bulging deformation of UHMWPE composite laminate under high-speed impact

The bulging test is crucial for evaluating the ballistic resistance of ultra-high molecular weight polyethylene laminate. However, the underlying deformation mechanism and the quantitative description of the bulging deformation, including the apex displacement and the location of the boundary of the deformation region (traveling hinge), are still lacking due to the complex dynamic elastic-plastic response under impact. In this paper, the bulging deformation of UHMWPE laminates is computationally and theoretically studied. First, an orthotropic elastic-plastic damage model considering the strain rate effect is established, which can describe the dynamic response of UHMWPE laminates in agreement with the experimental results. Secondly, the results show that the apex displacement increases linearly with the increase of impact velocity but decreases nonlinearly with the thickness. In contrast, the traveling hinge moves outward at a constant speed, independent of the thickness and impact velocity. It can be explained that the membrane stretching dominates the bulging deformation. Based on these results, an analytical model is proposed to quantitatively predict the bulging deformation, which can be used to predict the effects of the mass and the impact velocity and thickness on the bulging deformation. The work is meaningful for the design of UHMWPE laminates with high-impact resistance.

Studies on the stab resistance and ergonomic comfort behaviour of multilayer STF-treated tri-component woven fabric and HPPE laminate composite material

Research related to stab-resistant armour is focused on developing a low-weight flexible stab-resistant armour. Various materials and methods have been used to reduce the overall bulk but managing the flexibility and bulk with improved stab resistance is still a challenge for the researchers. In this study, flexible stab-resistant material for stab-resistant personal protective equipments (PPEs) has been developed by using shear thickening fluid (STF) treated fabric made of multicomponent yarns and ultra high molecular weight polyethylene (UHMWPE) laminate composite. The stab resistance and comfort behaviour like flexural rigidity and areal density were investigated with respect to number of layers and different STF concentrations according to VPAM KDIW-2004 and respective standards for flexural rigidity. Laminate-Woven hybrid composite was developed to reduce the bulk of the panel while maintaining the required protection level.

Anti-Penetration Performance of Composite Structures with Metal-Packaged Ceramic Interlayer and UHMWPE Laminate

The impact response of a composite structure consisting of a metal-packaged ceramic interlayer and an ultra-high molecular weight polyethylene (UHMWPE) laminate has been studied through a ballistic test and numerical simulation. The studied structure exhibits 50% higher anti-penetration performance than the traditional ceramic/metal structure with the same areal density. The metal-packaged ceramic interlayer and the UHMWPE laminate are key components in resisting the penetration. By using a metal frame to impose three-dimensional constraints on ceramic tiles, the metal-packaged ceramic interlayer can limit the crushing of the ceramic and contain the broken ceramic fragment to improve the erosion of the projectile. The large deformation of UHMWPE laminate absorbs a large amount of energy from the projectile. By decreasing the amplitude of the shock wave and changing the distribution of the impact load in the structure, the projectile has longer residence time on the interlayer. The anti-penetration performance shows within 10% variation when the impact position is varied. Due to the asymmetric deformation and high elastic recovery ability of the UHMWPE laminate, the projectile trajectory deflection is increased, and the broken ceramic fragments are restrained, thereby mitigating after-effect damage caused by the projectile after penetrating the structure.

Effect of Temperature and Ply Angle on Performance of Ultra High Molecular Weight Polyethylene (UHMWPE) Laminates Under Low Velocity Impact

Low velocity impact tests were conducted on ultra high molecular weight polyethylene (UHMWPE) laminates having different ply angle. The tests were conducted at various temperatures using steel impactor having 16mm diameter and hemi spherical shape. The selected impact energies are in the range of 50 to 250 Joule. The performance of the composites was compared with respect to peak force, maximum displacement and back face deformation. Results indicated that with increase of temperature, the contact duration increased whereas deceleration was reduced. Various failure mechanisms involved in energy absorption were also addressed.

Orthotropic vs quasi-isotropic: How the tape orientation influence the performance of disentangled polyethylene laminates

Disentangled ultrahigh molecular weight polyethylene (DPE) is a high-tenacity and high-modulus material having great potential for impact resistance applications. This research presents a comprehensive experimental study on the effect of orientation on the tensile and low-velocity impact performance of laminates produced from DPE tapes. The laminates were constructed by laying the DPE tape at different orientations followed by compression moulding. Quasi-isotropic laminate showed good tenacity in all directions whereas cross-ply orthotropic laminate showed the maximum tenacity in both the principal directions (0° and 90°). The impact energy absorption by the orthotropic laminate was 61.1% higher compared to that of quasi-isotropic laminate. The results imply that cross-ply laminate is the most suitable one for ballistic applications.

Multi-stage penetration characteristics of thick ultra-high molecular weight polyethylene laminates

To further reveal the failure mechanisms of thick ultra-high molecular weight polyethylene (UHMWPE) laminates, field firing tests were conducted for 10-, 20-, and 30-mm thick laminates against 12.7-mm calibre wedge-shaped fragment simulated projectiles at high velocities between 450 and 1200 m/s. The ballistic performance, deformation process, and staged failure characteristics of the laminates with different thicknesses were compared and analysed. The results demonstrate that the ballistic limits of the UHMWPE laminates increase almost linearly with laminate thickness. The 10-mm thick laminate generally experiences two-stage failure characteristics, whereas three-staged failure occurs in the 20- and 30-mm thick laminates and the progressive delamination is evident. The energy limit concept representing the maximum energy absorption efficiency and the idea of reuse of the thick UHMWPE laminates are proposed in this study. The findings of this research will be useful in the design of flexible and effective UHMWPE-based protective equipment.

Efficacy of various structural forms of disentangled polyethylene laminates against low velocity impact

Filament-based unidirectional laminates of para-aramid and ultra-high molecular weight polyethylene exhibit excellent impact resistance performance. This research explored the possibility of using disentangled polyethylene (DPE) tape, instead of filaments, as an alternative impact resistant material. The effects of laminate structure, binding resin content and processing temperature on the tensile and impact properties of cross-ply laminates prepared from DPE tape was investigated. Three types of cross-ply laminates prepared from tape, woven fabric of untwisted tape and woven fabric of twisted tape were explored. Tensile properties and low velocity impact resistance of laminates were evaluated. Laminate made from woven untwisted tape showed much lower impact energy absorption than cross-ply laminate, while the woven twisted tape based laminate performed the worst. Cross-ply laminates made with low resin content showed better tensile and impact resistance performances. Cross-ply laminates prepared at higher moulding temperature showed significantly enhanced impact energy absorption than its counterpart prepared at a lower temperature. Therefore, cross-ply laminate of DPE tape with low resin content is ideal for impact resistance applications.

Ballistic response of ultra-high molecular weight polyethylene laminate impacted by mild steel core projectiles

This paper presents the effect of interlaminar shear property on the ballistic response of ultra-high molecular weight polyethylene (UHMWPE) fiber composite laminate and discusses the detailed progressive ballistic damage process. Specifically, two kinds of UHMWPE fiber composite laminates with different interlaminar shear strength (ILSS) are impacted by a standard projectile (7.62 mm × 39 mm), and their multi-scale internal damage morphologies are characterized. Based on damage patterns, an evaluation model of laminate energy absorption is established to analyze the dissipation mechanism of the kinetic energy of the projectile. Results of ballistic tests indicate that the reduction of ILSS may result in the degradation of anti-penetration performance and in more serious internal damage. Internal damage morphologies show that shear fracture and delamination fracture are the primary failure modes during ballistic impact. The energy absorption by the laminate via tensile deformation, delamination failure and shear failure may account for 56.21%, 17.45%, and 16.49% of the projectile kinetic energy, respectively. Hence, tensile deformation may be the primary energy dissipation mechanism of projectile kinetic energy.

Heat sealing evaluation and runnability issues of flexible paper materials in a vertical form fill seal packaging machine

Vertical form fill seal machines are commonly used to form pouches. This paper aimed to optimize the sealing parameters and evaluate the runnability of flexible paper-based packaging materials with a polyethylene coating, differentiated by their grammages and thicknesses. This was done in comparison with a commercial plastic film, an oriented polypropylene and polyethylene laminate, using two different sealing jaw patterns in an industrial-scale vertical form fill seal machine. Based on the results obtained, the first observable seal was found at a sealing temperature of 90 °C for the paper-based material and a sealing temperature of 100 °C for thermoplastic film, both at a dwell time of 2 s. It was shown that the paper-based material had a larger sealing window, up to a sealing temperature of 220 °C, before the material started to turn brown, while the thermoplastic film shrank at a sealing temperature of 140 °C. Several peel and compression strength tests were performed to evaluate the flexible paper-based material. Furthermore, several hindering issues were observed in the paper-based material during the production runs. These included wrinkling, web buckling, friction in the forming tubes, pouches airtightness, etc. As such, recommendations for further investigations and future studies are given.

Experimental and numerical study on the ballistic performance of ultrahigh molecular weight polyethylene laminate

AbstractUltrahigh molecular weight polyethylene (UHMWPE) fiber orthogonally laid laminate is widely used in ballistic protection due to its excellent properties. Research on its response under bullet impact is meaningful for understanding the antiballistic mechanism and designing personal protection. In this article, three‐dimensional digital image correlation measurement and analysis method is applied to study the response of UHMWPE orthogonally laid laminates under the impact of pistol bullets. A corresponding smoothed particle hydrodynamics (SPH)–finite element method coupled numerical model is established to study the impact phenomenon. The bullet model is developed using the SPH method. The laminate is developed with multiple equivalent sublaminate finite element models. The experimental results show the damage mode and back‐face features of the laminate. First, the damage mode has two stages: the first stage includes a small number of layers that are penetrated on the impact surface and the second stage includes the expansion of the back‐face deformation. Second, the average maximum bulge height in three repeated experiments is 14.59 mm. Third, the average maximum velocity of the bulge apex position in experiments on the z‐axis is 92.32 m/s. Fourth, the maximum and minimum back‐face in‐plane shear values are 0.0893 and −0.0928, respectively. Finally, the numerical results have good agreement with the experimental results and show that the compression waves mainly propagate along the x and y directions. The experimental results can provide quantifiable features for studying the impact responses of UHMWPE laminates. The numerical model could be applied to study features that cannot be measured by experiments.

Improving Interlayer Adhesion of Poly(p-phenylene terephthalamide) (PPTA)/Ultra-high-molecular-weight Polyethylene (UHMWPE) Laminates Prepared by Plasma Treatment and Hot Pressing Technique.

Poly(p-phenylene terephthalamide) (PPTA) is a high-performance polymer that has been utilized in a range of applications. Although PPTA fibers are widely used in various composite materials, laminar structures consisting of PPTA and ultra-high-molecular-weight polyethylene (UHMWPE), are less reported. The difficulty in making such composite structures is in part due to the weakness of the interface formed between these two polymers. In this study, a layered structure was produced from PPTA fabrics and UHMWPE films via hot pressing. To improve the interlayer adhesion, oxygen plasma was used to treat the PPTA and the UHMWPE surfaces prior to lamination. It has been found that while plasma treatment on the UHMWPE surface brought about a moderate increase in interlayer adhesion (up to 14%), significant enhancement was achieved on the samples fabricated with plasma treated PPTA (up to 91%). It has been assumed that both surface roughening and the introduction of functional groups contributed to this improvement.

Experimental and microstructure analysis of the penetration resistance of composite structures

Abstract Composite structures (SiC/UHMWPE/TC4; SiC/TC4/UHMWPE) were designed using silicon carbide (SiC)ceramics, ultra-high-molecular-weight polyethylene (UHMWPE) laminate, and titanium alloys (TC4s). Penetration experiments and numerical simulations were carried out to study the anti-penetration mechanism and energy characteristics of the composite structures, and the microstructure of the TC4 was analyzed. The results show that the two composite structures designed have advantages in reducing mass and thickness. The energy proportion of the TC4 is the largest among the three materials, which mainly determines the anti-penetration performance. The microstructure of the TC4 in composite structure I shows rough edges of bullet holes, a large number of adiabatic shear bands (ASBs), ASB bends and bifurcates, and many cracks, which lead to spalling damage of the TC4. The microstructure of the TC4 in composite structure II shows flat edges of bullet holes, several straight ASBs, and no cracks, which leads to brittle fragmentation. The initiation, expansion, combination of ASBs and cracks lead to more energy consumption. Therefore, the combination form of composite structure I can give full play the energy dissipation mechanism of the TC4 and has better anti-penetration performance than composite structure II.

Ballistic performance of ultra-high molecular weight polyethylene laminate with different thickness

To explore the influence of thickness on the protective performance and damage mechanism of ultra-high molecular weight polyethylene (UHMWPE) laminates penetrated by 7.62 × 39 mm steel core bullets, field firing tests were carried out for 10-, 20-, and 30-mm-thick laminates at 10°C. The deformation and failure process, final failure state and deformation degree, and cross-section of the opening holes of different thickness UHMWPE laminates were analyzed and compared to determine the protective capability and failure mechanism of the laminates. The results show that the ballistic responses of the UHMWPE laminates with different thicknesses vary significantly, and that the protective capability of the UHMWPE laminates was improved with the increase in the laminate thickness. The 10-mm-thick UHMWPE laminate was perforated by the bullet, while the 20- and 30-mm-thick laminates were not. The 10-mm-thick laminate shows two-stage failure characteristics, while the 20- and 30-mm-thick laminates exhibit three-stage failure characteristics that are different from each other. The largest back-face deformation depth of 17.50–21.25 mm was obtained for the 20-mm-thick laminate, while the deformation of the 30-mm-thick laminate is negligible. It is suggested that the functions and application scenarios for the UHMWPE laminates with different thicknesses are different due to their different protective properties and failure mechanisms.