As one of the most widely used personal protective equipment(PPE),body armors play an important role in protecting the human body from the high-velocity impact of bullets or projectiles.The body torso and critical org...As one of the most widely used personal protective equipment(PPE),body armors play an important role in protecting the human body from the high-velocity impact of bullets or projectiles.The body torso and critical organs of the wear may suffer severe behind-armor blunt trauma(BABT)even though the impactor is stopped by the body armor.A type of novel composite material through incorporating shear stiffening gel(STG)into ethylene-vinyl acetate(EVA)foam is developed and used as buffer layers to reduce BABT.In this paper,the protective performance of body armors composed of fabric bulletproof layers and a buffer layer made of foam material is investigated both experimentally and numerically.The effectiveness of STG-modified EVA in damage relief is verified by ballistic tests.In parallel with the experimental study,numerical simulations are conducted by LS-DYNA®to investigate the dynamic response of each component and capture the key mechanical parameters,which are hardly obtained from field tests.To fully describe the material behavior under the transient impact,the selected constitutive models take the failure and strain rate effect into consideration.A good agreement between the experimental observations and numerical results is achieved to prove the validity of the modelling method.The tests and simulations show that the impact-induced deformation on the human body is significantly reduced by using STG-modified EVA as the buffering material.The improvement of protective performance is attributed to better dynamic properties and more outstanding energy absorption capability of the composite foam.展开更多
Ba1-xSrxTiO3（BST）powders were fabricated by sol-gel process by using strontium carbonate for the substitution of strontium acetate.Barium acetate,strontium carbonate and titanium-tetrabutoxide were used as raw mater...Ba1-xSrxTiO3（BST）powders were fabricated by sol-gel process by using strontium carbonate for the substitution of strontium acetate.Barium acetate,strontium carbonate and titanium-tetrabutoxide were used as raw materials.The BST gel was studied by thermal analysis techniques,the physical structure of the BST powders was measured by XRD and the grain size was measured.The results showed that the powders possess a single perovskite phase after 700℃ and the ideal powder size even after 800℃ calcining.This indicated that the powder can be used for BST ceramics and the fabrication of the sol-gel derived BST can be carried out well by using carbonate as the starting materials.展开更多
基金the National Natural Science Foundation of China(Grant Nos.12072356 and 12232020)the Science and Technology on Transient Impact Laboratory(Grant No.6142606221105)the Beijing Municipal Science and Technology Commission(Grant No.Z221100005822006).
文摘As one of the most widely used personal protective equipment(PPE),body armors play an important role in protecting the human body from the high-velocity impact of bullets or projectiles.The body torso and critical organs of the wear may suffer severe behind-armor blunt trauma(BABT)even though the impactor is stopped by the body armor.A type of novel composite material through incorporating shear stiffening gel(STG)into ethylene-vinyl acetate(EVA)foam is developed and used as buffer layers to reduce BABT.In this paper,the protective performance of body armors composed of fabric bulletproof layers and a buffer layer made of foam material is investigated both experimentally and numerically.The effectiveness of STG-modified EVA in damage relief is verified by ballistic tests.In parallel with the experimental study,numerical simulations are conducted by LS-DYNA®to investigate the dynamic response of each component and capture the key mechanical parameters,which are hardly obtained from field tests.To fully describe the material behavior under the transient impact,the selected constitutive models take the failure and strain rate effect into consideration.A good agreement between the experimental observations and numerical results is achieved to prove the validity of the modelling method.The tests and simulations show that the impact-induced deformation on the human body is significantly reduced by using STG-modified EVA as the buffering material.The improvement of protective performance is attributed to better dynamic properties and more outstanding energy absorption capability of the composite foam.
文摘Ba1-xSrxTiO3（BST）powders were fabricated by sol-gel process by using strontium carbonate for the substitution of strontium acetate.Barium acetate,strontium carbonate and titanium-tetrabutoxide were used as raw materials.The BST gel was studied by thermal analysis techniques,the physical structure of the BST powders was measured by XRD and the grain size was measured.The results showed that the powders possess a single perovskite phase after 700℃ and the ideal powder size even after 800℃ calcining.This indicated that the powder can be used for BST ceramics and the fabrication of the sol-gel derived BST can be carried out well by using carbonate as the starting materials.
