At present, countries in the world are constantly developing and optimizing various types of new anti-ballistic materials to enhance the ballistic protection performance of vehicles and individual soldiers. High-performance fiber composite materials have the characteristics of light weight, high strength, and excellent elasticity resistance. They are the most researched, fastest-growing and most promising ballistic materials. Military developed countries represented by the United States pay special attention to the development of high-performance ballistic fiber and composite materials. Defense research institutions such as the US Army Research Laboratory and universities funded by the Department of Defense have carried out a lot of research work in recent years. This article mainly introduces the development, application status and performance level of glass fiber, aramid fiber, ultra-high molecular weight polyethylene fiber, carbon fiber, PBO and M5 fiber and their composite materials abroad.
Glass fiber (GF) has high tensile strength, high elongation at break, good impact performance, fatigue resistance, and chemical stability. The disadvantage is that it is relatively dense. GF composite material is the first generation of relatively inexpensive ballistic armor material. The armors of the American "Bradley" infantry fighting vehicle, the Russian T90S main battle tank and the Indian "Arjun" main battle tank all use GF interlayer. The dry strings of the US Navy's "Wasp" class amphibious assault ship and the Russian "Kuznetsov" aircraft carrier also use GF composite anti-ballistic protection structures. E-glass fiber (E-GF) and S-2 fiberglass (S-2GF) are two types that are often studied and applied. S-2GF has higher strength and elongation than E-GF.
Grujicic et al. studied the anti-penetration elastic performance of S-2GF reinforced phenolic resin/alumina ceramic armor, and found that this composite armor has an excellent ceramic/composite areal density ratio and has high anti-elasticity performance against armor-piercing bullets. RajuMantena et al. studied the anti-explosive impact performance of a new generation of GF polymer-based composite materials for ships. The sandwich composite panel made of E-GF, Dow510A-40 vinyl bromide, and Tycor, polyvinyl chloride The core layer is composed of foam and balsa.
Michigan State University in the United States has conducted extensive research on GF reinforced polymer matrix composites and submitted a report to the Army Research Laboratory. It prepared a composite material based on S-2GF/SC-15 epoxy resin; studied the effect of the size effect of the composite material composed of orthogonal flat-woven GF felt cloth and epoxy resin matrix on the behavior under high-pressure loads; developed The high impact three-axis quasi-three-dimensional woven composite material based on GF and its impact test show that the stiffness of the three-axis quasi-three-dimensional composite material is 12.5% and 20% higher than that of the two-dimensional woven and laminated samples, respectively; The resin transfer molding process prepared the SC-15 epoxy resin composite board reinforced with glass fiber mat for vehicle protection panels. The average tensile modulus and tensile strength were 20.06GPa and 383.65MPa, respectively, and the average compressive modulus and compressive strength were respectively They are 31.83 GPa and 258.60 MPa, the average shear modulus and shear strength are 5.62 GPa and 97.43 MPa, respectively, and the average flexural modulus and bending strength are 16.23 and 334.61 MPa, respectively; finally they also used S-2GF felt fabric to make a preform The preform is impregnated with SC-15 epoxy resin using a vacuum assisted resin transfer molding process to produce a composite bumper bracket for vehicles.
The US Army Engineering Research and Development Center also studied the energy dissipation and high strain rate dynamic response of E-GF composites loaded with carbon nanotubes. They grow carbon nanotubes on the E-GF felt, and then combine the E-GF felt loaded with carbon nanotubes with resin to form a composite material. Tests on the mechanical properties and ballistic properties of the material show that the composite material loaded with carbon nanotubes can increase the specific absorption energy by 106% at high strain rates, and the energy density dissipation increases by 64.3% after 5 cycles at quasi-static strain rates, and the V50 value An increase of 11.1%.
2. Aramid fiber
Aramid fiber has the characteristics of high specific strength and high elongation at break. Under the same areal density, the elasticity of aramid/resin composite is 2~3 times that of GF/resin composite, which can be comprehensive in many fields. Replace GF/resin composite materials.
United States Clemson University Joint Army Research Laboratory and other institutions used traditional finite element method to perform numerical analysis on KevlarKM2 ballistic fiber felt to determine the penetration resistance of the material and the overall deflection, deformation, and failure response to impact. The team’s Grujicic and others have further optimized and upgraded the ballistic impact/explosion protection calculation and analysis model of plain-woven Kevlar fiber-reinforced polymer matrix composites. In 2014, Grujicic et al. also studied the relationship between the microstructure/performance of PPTA (polyparaphenylene terephthalamide)-based materials, and developed a multi-length-scale calculation method to determine the effects of various microstructure features on PPTA at different scales. The impact of the macroscopic ballistic anti-penetration performance of the base felt cloth or PPTA fiber reinforced polymer matrix composite material.
Italy Cassino and University of Southern Lazio Sorrentino, etc. combined Kevlar29 plain weave felt with thermosetting resin to make laminates, and carried out Walker numerical model prediction and ballistic performance tests on the prepared composite armor. The U.S. Army Research Laboratory O'Brien and others prepared a composite material with a light transmittance of about 40% using a flat strip-shaped transparent nylon monofilament as a reinforcement and a transparent epoxy resin matching the refractive index as a matrix. , And conduct ballistic experiments on the material, and the V50 value of the material obtained is greater than 305m/s, which is much higher than epoxy resin and polycarbonate.
The United States Sandia National Laboratory Song et al. studied the effect of twist on the transverse impact performance of KelvlarKM2 elastic fiber yarn, and used a high-speed camera to measure the Euler transverse wave velocity caused by the impact. The results show that the Euler transverse wave speed increases with the increase in the number of fiber yarn twists, which means higher ballistic performance. Therefore, the use of twisted fiber yarn in the ballistic fiber felt can improve the ballistic properties of the material. Wong et al. studied the effect of magnetic field on the ballistic properties of aramid fibers and ultra-high molecular weight polyethylene fibers. The researchers sandwiched aramid fiber (Kevlar K29) and ultra-high molecular weight polyethylene fiber between two sets of opposite rare earth magnets to test the effect of magnetic repulsion on the ballistic properties of the material. The results show that the magnetic repulsion can restrain bullets from entering the front panel of aramid fiber.
Nano-modification of aramid fiber or nano-filling of its composite material can also improve the anti-elasticity performance. Sodano et al. enhanced the interface strength by growing vertical ZnO nanowires on the surface of Kevlar fibers. The interface strength of the fiber is 96.9% higher than that of the bare fiber, and the peak load of the pull-out test is increased by 6.5 times. ZnO nanowires strengthen the pull-out performance of Kevlar fibers, which in turn also improves the ballistic impact protection level of the material. ManeroII et al. studied the impact of nano-particle fillers on Kevlar29 impact-resistant composite materials, and conducted V50 ballistic testing on Kevlar29 fiber composites filled with ground carbon fibers and nanoparticles (carbon nanotubes and core-shell rubber particles). The results show that the nano-core shell rubber particle filler is effective for energy absorption during impact due to cavitation, and at the same time significantly improves the ballistic performance. Carbon nanotube filler can improve the matrix-fiber interface performance, and also significantly improve the ballistic performance. Both can enhance the V50 anti-elasticity performance of composite materials. Adding 1% of the mass fraction of ground carbon fiber to the composite material and adding 1% of nanoparticles can increase the V50 by 7.3% (carbon nanotubes) and 8% (core-shell rubber particles) compared to the reference sample.
3. Ultra-high molecular weight polyethylene fiber
Ultra-high molecular weight polyethylene fiber has low density, good moisture absorption resistance, and high elongation at break. It is one of the fibers with the best specific strength that has been commercialized. Dyneema is an ultra-high molecular weight polyethylene composite material produced by Dyneema in the Netherlands. It is one of the main commercial materials for future combat systems to achieve lightweight and protective performance. The company's hard and lightweight bulletproof composite material reinforced by Dyneema HB26 polyethylene fiber is 40% stronger than aramid. Hardwire LLC of the United States used Dyneema HB26 and HB50 ultra-high molecular weight polyethylene fibers to develop and demonstrate a vehicle explosion-proof system.
A lot of research on Dyneema fiber and composite materials has been done abroad. Sanborn et al. used the direct grip method to test the tensile properties of Dyneema SK76 single fiber under multiple load rates, and solved the problem that the fiber diameter is too small and the surface energy is too low to be accurately measured by the traditional adhesion method. Greenhalgh et al. studied the micro-sections of different DyneemaHB26 orthogonal laminated composite laminates under ballistic impact and deduced the sequence of failure modes such as delamination, layer cracking and fiber kinking during the impact process, and obtained the main energy absorption fracture process. And determine how these processes are affected by the preparation conditions and target response. Karthikeyan et al. studied the damage mechanics and interface effects of HB26 laminates with different areal densities to evaluate the material's limit speed and failure mechanism. O'Masta et al. studied the continuous penetration deformation and fracture mechanisms of HB50 and BT10m composite laminates reinforced by Dyneema ultra-high molecular weight polyethylene fibers and molecularly oriented strips, and discussed the HB50 fiber and BT10m strip reinforcement. The difference. Rosso et al. used Dyneema SK75, Dyneema SK76 and Kevlar49 to manufacture micro-woven fabrics with different skewness and configurations, and evaluated the ballistic properties of polymer matrix composites reinforced by different micro-woven fabrics through a series of impact tests. The results show that the ballistic limit of the polymer composite reinforced by the micro-woven fabric is nearly 20% higher than that of the orthogonal laminated composite made of unidirectional fibers.
Sapozhnikov et al. compared the fragment ballistic properties of homogeneous and hybrid thermoplastic composites with different structures at different temperatures. The composition of these composite systems is a multilayer aramid felt cloth (Twaron, RUSLAN-SVM)/low density polyethylene matrix composite laminate. Based on Dyneema (HB2, HB80) multilayer ultra-high molecular weight polyethylene system, and hybrid aramid/DyneemaHB2, DyneemaHB2/DyneemaHB80 laminates. The results show that temperature has little effect on the V50 value of aramid felt cloth/low-density polyethylene and ultra-high molecular weight polyethylene composites, but the divergence of experimental data increases at low temperatures. Under high-speed impact, the V50 value and absorption energy of laminates based on ultra-high molecular weight polyethylene fibers are better than other materials. But when the projectile's velocity exceeds the ballistic limit, its energy absorption capacity drops sharply.
In addition, Zhou et al. also studied the influence of yarn gripping on the ballistic properties of UHMWPE felts, and clarified the feasibility of creating a new felt structure that can effectively enhance the friction between yarns. Nguyen et al. studied the ballistic performance of UHMWPE composite panels with different thicknesses against two kinds of caliber fragments. Studies have shown that as the thickness of the target plate increases, the sample exhibits two stages of penetration: the first stage is the initial shearing plugging, the penetration occurs during fiber shear, and the target plate does not flex; the second stage It is a bulge, the sublayer detaches from the target plate and undergoes large deflection and penetration during fiber stretching. The researchers carefully studied the two stages of penetration and developed an analytical model to describe them.
4. Carbon fiber
The Young's modulus of carbon fiber is usually more than three times that of traditional glass fiber and about twice that of Kevlar fiber. It has important application potential in lightening military equipment and improving survivability. In 2015, Chae of Georgia Institute of Technology in the United States developed a new process for the preparation of continuous carbon fiber by gel spinning based on polyacrylonitrile (PAN) spinning technology. The average tensile strength of the prepared PAN-based carbon fiber is 5.5~5.8GPa The tensile modulus is between 354~375GPa. The tensile modulus is 25%~36% higher than IM7 type PAN-based carbon fiber widely used in aerospace. The combination of strength and modulus is PAN-based continuous The highest value combination of carbon fiber. In the future, by optimizing materials and processes, the strength and modulus of PAN-based carbon fibers will be improved simultaneously.
Wang et al. studied the remaining strength of the structure of Hexcel carbon fiber composites when subjected to ballistic impact. They used projectiles of different calibers to conduct ballistic tests on the materials under low-speed and high-speed impacts, and observed the damage degree of the specimens, and then prepared the tensile strength after impact. Extend, compress and shear samples, and conduct mechanical tests. The results show that at an impact velocity significantly higher than the ballistic limit, the residual strength of the specimen with ballistic impact damage is significantly lower than that of the original specimen, but not significantly lower than the specimen with a machined hole with the same caliber as the projectile. Research on the ballistic damage of carbon fiber polymer composites is very important for aircraft design and damage repair.
Lawrence and others are committed to the research of knitted carbon fiber (T300) composite materials. The purpose is to reduce the attenuation of the in-plane performance of the material through the development of knitting technology. These in-plane properties are related to the reinforcement technology along the thickness direction, including Z-direction reinforcement technology and stitching. And tufting technology. Researchers have developed a unique internal knitting process, which enables z-direction fibers to be embedded into the composite laminate at different angles (±45/90°), effectively reducing the loss of tensile strength and significantly improving the compressive strength.
5. Glass fiber-carbon fiber hybrid
Boyd et al. studied the multi-impact durability of carbon fiber-glass fiber/epoxy resin hybrid composites toughened by thermoplastic polyurethane interlayer membranes. The specific content includes thermoplastic polyurethane (TPU) interlayer toughened non-wrinkle IM7 carbon fiber-S2 glass fiber The preparation process of hybrid composite laminate and its influence on impact performance. The results show that the TPU toughened hybrid material can be successfully prepared by vacuum-assisted resin transfer molding and curing/post-curing processes, and the process has almost no or few distortions and defects. The sample showed good performance in the impact test, but it is still necessary to develop a model to fully study the reinforcement mechanism of the TPU interlayer.
In order to study the effect of three-dimensional braided structure on the mechanical properties of materials, Justusson et al. conducted mechanical tests on the prepared carbon fiber-glass fiber three-dimensional hybrid fabric composite and its SC-15 epoxy resin matrix. The study found that the braided configuration is critical to the failure of the two composite materials under tensile load; the carbon fiber/glass fiber hybrid composite material is less balanced in the two directions, and the strength and modulus in the warp direction are higher than that of the weft. The direction is much higher, and the failure types in the longitudinal and dimensional directions are different.
Muoz et al. produced a flat composite material by vacuum impregnating epoxy-vinyl ester into a hybrid three-dimensional orthogonal woven preform. The upper four layers of the preform are glass fibers, the lower two layers are AS4C carbon fibers, and the glass fiber and carbon fiber layers are hybrid layers oriented in the filling direction. The study found that if the carbon fiber surface of the sample is impacted, the energy dissipation of the hybrid three-dimensional composite material will be increased.
PBO (poly-p-phenylene benzobisoxazole) fiber was originally developed by the U.S. Air Force, and later Zylon products were manufactured by Japan’s Toyobo Company. PBO fiber is known as the future ultra-high performance fiber that can replace aramid fiber. The density of this kind of fiber is lower than that of aramid fiber, and its mechanical properties and environmental resistance are far better than Kevlar and other aramid fibers.
In 2006, the University of California signed a contract with the U.S. Army to conduct ballistic tests to determine the elastic properties of Zylon fibers. The results show that Zylon fiber has better performance than Kevlar29, and when used in armor, it will effectively enhance protection performance and mobility. Although PBO fiber has the advantages of light weight, high strength and high modulus, it is limited by the degradation of mechanical properties during use in protection applications. To solve this problem, Tamargo-Martínez et al. developed a supercritical CO2 chemical reagent diffusion post-treatment process to treat PBO fibers to reduce the rate of decline of their mechanical properties and extend their service life. Lesser of the University of Massachusetts Amherst studied the stabilized PBO fiber after supercritical CO2 post-treatment, using supercritical CO2 as an extractant to extract the phosphoric acid and water remaining on the PBO fiber, and using it as a medium to introduce a variety of substances Neutralize phosphoric acid and weaken the degradation effect of water and acid on PBO fiber.
The overlapping of elastic fibers may be a factor of performance degradation. McDonough et al. studied the effect of folded anti-bullet PBO fiber performance attenuation, and determined the effect of this failure mechanism on armor protection performance through experiments. They also further studied the influence of folding against the internal structure of elastic fibers. Japan Horikawa et al. have done a lot of research on PBO fibers. For example, they studied the tensile and fatigue strength of high modulus PBO fibers through heat treatment, and studied the effect of shear rate on the tensile strength of high modulus PBO fibers.
M5 (poly-2,5-dihydroxy-1,4-phenylenepyridodiimidazole) fiber is developed by AkzoNobel. Its structure is similar to PBO, but the molecule contains hydroxyl groups, so hydrogen bonds can be formed between macromolecular chains and compressed Performance is better than PBO.
The University of Delaware and the Army Research Laboratory conducted a series of basic research on M5 fiber. First of all, infrared spectroscopy and kinetic studies were carried out on the formation of intermolecular hydrogen bonds in M5 fibers. The results showed that heat treatment promoted the formation of hydrogen bonds between polymer chains in the fibers. It was calculated that the hydrogen bonds between molecular chains were formed and activated. It can be 14.8kJ/mol; the interface behavior of the three high-performance fibers of M5 KevlarKM2 and Armos has been compared and studied, and the results show that M5 exhibits higher interfacial shear strength than other fibers; the effect of hydrogen bonding and water cycle is also studied. It is found that the increase of hydrogen bonds will increase the compressive strength of the fibers due to the influence of the compressive properties of M5 fibers. The water cycle experiment revealed the reversibility of some hydrogen bonds in the material.