A ballistic-resistant material is a composite based on a high-strength and high-modulus fiber, and is generally applied in individual protection, such as body armors. The ballistic-resistant material is mainly classified as soft and hard ballistic-resistant materials, which have different ballistic-resistant mechanisms. The hard ballistic-resistant material mainly utilizes its hardness to alter the shape of a bullet or fragment, thereby reducing the kinetic energy thereof and producing a ballistic-resistant effect, while the soft ballistic-resistant material mainly utilizes the deformation of the soft ballistic-resistant material to produce a buffering effect, to absorb the kinetic energy of a bullet or fragment shot thereon, thereby achieving the ballistic-resistant purpose.
The ballistic-resistant material may have a structure composed of unidirectional high-strength and high-modulus fibers, such as high-strength and high-modulus polyethylene fibres or aramid fibres. Such a ballistic-resistant material has a ballistic-resistant performance to some extent; however, since the resin adhesive used in each layer of the ballistic-resistant material is a single resin system, the ballistic-resistant material is either too soft, which makes the material easily be penetrated when subjected to the breakthrough of a steel core bullet; or is too hard, which makes the wearer feel uncomfortable.
U.S. Pat. No. 7,378,147 has disclosed using a dynamic mechanical analysis (DMA) test method to test the loss modulus of polyethylene yarns. The dynamic mechanical analysis is a technology of applying a dynamic stress or strain to a sample and analyzing the response so as to obtain mechanical performances such as a storage modulus (E′), loss modulus (E″) and damping (tan δ) as a function of the temperature and/or frequency.
The storage modulus is a capability that a material is able to store the energy applied thereon for further use or for use during rebound deformation. The loss modulus is a capability that a material is able to dissipate the energy applied thereon, for example, the energy lost due to failure to return to its original shape after plasticine being stretched. The tan δ is a ratio of the storage modulus to the loss modulus.
For the test on the loss modulus in U.S. Pat. No. 7,378,147, a peak value of the loss modulus was obtained at a frequency of 10 or 100 radians/second, within a temperature range of −150° C. to 125° C. and under a strain value of 0.025±0.005%.
Although the loss modulus of a ballistic-resistant fibre is associated with the ballistic-resistant performance, there has been no report on the correlation between its loss modulus and the loss modulus of a resin adhesive.
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