The impact of different target plate structural forms on anti-fragment and anti-ballistic properties
May 25, 2024
Table 4 gives a comparison of the anti-fragment performance of several target plates with different structural forms. The comparison is based on the overall surface density of the target plate (different from the density of the single layer of the target plate). The fragmentation speed during the experiment was about 600m/s. According to statistics from limited sources, the V50 setting value of individual anti-fragment bulletproof products of various countries, especially helmet composite materials. The US military's PASGT helmet V50 is 610m/s, the German army is 620m/s, the French army is 680m/s, South Korea is 609m/s, and China's new composite helmet V50 is 610m/s. In Table 4, the glue content of CT709 laminate is 12%, and the other target plate samples are simple laminates.
It can be seen from the results in Table 4. Under the condition that the overall surface density of the target plate is certain. Only in terms of ballistic resistance. The simple laminated sample of ultra-high molecular weight polyethylene fiber orthogonally laid composite material (spectra shielded Plus LCR) has the highest anti-fragmentation ability. This is followed by CT709 laminated fabrics and laminates. Stack the target again for a combination of yellow and white flakes. The worst is the single yellow chip laminated target plate.
For anti-fragmentation, the following information and discussion can also be obtained from Table 4:
The axial tensile mechanical properties of ultra-high molecular weight polyethylene Spectra2000 fiber are more than 2 times higher than that of para-aromatic polyamide fiber. However, the anti-fragment V50 of the laminated white film with the same overall surface density of the target is only about 16% higher than that of the laminated yellow film. The laminated white film is only 2% higher than the CT709 laminated fabric. This shows that the excellent tensile mechanical properties of ultra-high molecular weight polyethylene fiber have not been fully utilized. This is closely related to the low transverse mechanical properties (compression and shear) of ultra-high molecular weight polyethylene fibers and their low melting temperature.
Under the same target surface density conditions, the anti-fragment ability of the yellow film simple laminated target board is not as good as the CT709 laminated fabric. The main reason is that the yellow target plate is an orthogonal laminate composite material with a resin content of more than 20%, and the equivalent fiber content is lower than the CT709 laminated fabric. Although the fiber straightness in the yellow sheet is higher than that of the laminated fabric, its fiber energy diffusion capacity is higher than that of the laminated fabric. However, its fiber strain energy contribution is lower than that of laminated fabrics, and the comprehensive bulletproof effect is the combination of these two factors.
Compared with CT709 fabric laminated composite materials and CT709 laminated fabrics with the same overall surface density of the target plate, the anti-fragmentation capabilities of the two are basically the same. Although the laminated composite material and the laminated fabric target plate have the same number of fabric layers, the anti-fragment V50 of the former is 50-70M/S higher than that of the latter (see Table 3). This also shows that fabric or fiber is the main reason for the improvement of anti-fragmentation ability, while the contribution of the matrix to anti-fragmentation ability is limited.
Through a balanced combination of yellow flakes and white flakes, superior anti-fragmentation properties can be obtained compared to yellow flakes alone. Although the pure white film has better anti-fragment penetration or penetration ability. However, it is bulky and expensive, and its excellent tensile mechanical properties have not been fully utilized. So simply laminating white sheets is not a good material selection method. And two materials (yellow film and white film) can achieve the best balance of performance, weight and price. For the combination of white film in front and yellow film in the back, its anti-fragmentation ability is much lower than the combination of yellow film in front and white film in the back. The main reason is that the ultra-high molecular weight polyethylene at the front of the target plate will undergo non-tensile fracture due to local high pressure, so its excellent tensile mechanical properties cannot be fully utilized. Another reason is that the ultra-high molecular weight polyethylene fiber with higher strength, modulus and elongation at break can fully exert its tensile mechanical properties at the rear. (It can be seen from the observation of the damage morphology that the fiber fracture at the rear of the target plate is mainly a tensile fracture mode). On the other hand, the stress wave transmission speed in high modulus and low density ultra-high molecular weight polyethylene fibers is higher than that in para-aromatic polyamide fibers, which is conducive to the effective diffusion of stress waves (strain energy).
