Effect of quilting pitch and sewing thread type on the fragment protective performance of para-aramid fabrics used in military body armour

Abstract

Personal protective equipment (PPE) is crucial for military personnel who find themselves in hostile situations facing a prolific and focused enemy. PPE is designed to protect the wearer from injury and/or fatality, i.e. the use of PPE increases the likelihood of survivability. Military body armour, which protects the critical organs of the torso, contains multiple layers of para-aramid or ultra-high molecular weight polyethylene (UHMWPE) fabrics. These layers of fabric are often quilted for ease of handling during the construction of the armour and to prevent the slumping of the armour layers in the carrier and protect the wearer from fragmentation which is the major cause of injury in modern warfare. Minimal work has been published on the effect of quilting on the protection offered by military body armour. In this work, the effects of quilting pitch (none; bias direction −10, 20 and 30 mm pitch), sewing thread type (cotton, polyester-cotton, para-aramid, bonded nylon) and the number of layers (one, three) of a Twaron® fabric on the fragment protective performance was investigated with reference to military body armour systems. Evidence of a strain rate effect was noted. Use of 100% cotton or bonded nylon thread for quilting typically resulted in a higher energy dissipated (ED ) compared to not-quilted specimens. The greatest improvements were noted with bonded nylon quilted specimens. At slower velocities, this improvement was 94% for one-layer specimens and 32% for three-layer specimens. At faster velocities, this improvement was 41% for one-layer specimens and 32% for three-layer specimens.