NUMERICAL SIMULATIONS OF FABRIC SHIELDS FOR BULLETPROOF VEST: DETERMINING THE NUMBER OF SHEETS TO WITHSTAND BALLISTIC IMPACTS

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ALEX ALVES BANDEIRA

Abstract

THE BASIC AIM OF THIS RESEARCH IS TO STUDY FABRIC SHIELDS FOR BULLETPROOF VEST AND DETERMINE THE NUMBER OF SHEETS NECESSARY TO RESIST THE BALLISTIC IMPACT. FOR THIS PURPOSE, A SOPHISTICATED NUMERICAL ALGORITHM IS USED. NEW CONSTITUTIVE EQUATIONS ARE DEVELOPED CAPABLE TO TAKE INTO ACCOUNT THE MATERIAL DAMAGE, THE YIELD STRESSES AND THE RUPTURE LIMITS. THIS IS BASED ON ELASTOPLASTICITY THEORY, WITH AN ADAPTATION OF THE FUNCTION RELATED TO THE HARDENING OF THE MATERIAL. WITH THIS, IT IS POSSIBLE TO CONTROL THE LIMITS OF THE PERMISSIBLE STRESSES ON THE YARN AND ON THE COATING OF THE STRUCTURAL FABRIC AND ACCURATELY REPRESENT THE PHYSICAL BEHAVIOR OF THE MATERIALS USED. IN THIS WAY, THE ELASTOPLASTICITY AND DAMAGE THEORIES ARE DEVELOPED IN THIS ARTICLE AND, FINALLY, A NUMERICAL ALGORITHM IS PRESENTED FOR THE DETERMINATION OF STRESSES, DISPLACEMENTS AND MATERIAL DEFORMATIONS. A TENSORIAL FINITE ELEMENT FORMULATION IS PRESENTED TO MODEL A FABRIC SHIELD SEGMENT AND THE PROJECTILE IS MODELED AS A RIGID SPHERE. THEREAFTER, THE MECHANICAL CONTACT FORMULATION IS DEVELOPED TO SIMULATE THE IMPACT BETWEEN A PROJECTILE AND A FABRIC SHIELD. FINALLY, THE ITERATIVE SOLUTION ALGORITHM IS PRESENTED. BASICALLY, THIS ARTICLE ALSO HAS THE PURPOSE OF MAKING A COMPLETE BIBLIOGRAPHICAL REVIEW OF THE FORMULATIONS USED SO FAR ON THE BALLISTIC IMPACT IN FABRIC SHIELDS AND, COMPARE THESE RESULTS WITH THE OBTAINED BY THE COMERCIAL PROGRAM LS-DYNA AND THE ONES OBSERVED IN LITERATURE. THE RESEARCH IS COMPLETED BY PRESENTING NUMERICAL EXAMPLES WITH THE OBJECTIVE TO MODEL THE BALLISTIC IMPACT BETWEEN A PROJECTILE AND A FABRIC SHIELD (BULLETPROOF VEST). THIS BULLETPROOF VEST IS SIZED SO AS TO COMPLETELY STOP THE PROJECTILE SHOT BY AN ASSAULT RIFLE. THE AUTHORS CONCLUDE BY STATING THE EFFICIENCY OF THE FORMULATIONS, THE GOOD PERFORMANCE OF THE ALGORITHMS AND THE PRECISION BETWEEN THE OBTAINED RESULTS, EVEN WHEN COMPARING WITH EXPERIMENTAL ONES. THE THEORIES PRESENTED AND THE RESULTS OBTAINED ARE EXTREMELY RELEVANT FOR THE SCIENTIFIC DEVELOPMENT OF THIS RESEARCH FIELD.

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