Bullet-proof helmet - mfd. from two rigid shells having composite interlayer of elastic foam and aromatic polyamide

摘要

A bullet-proof helmet is made from two rigid concentric shells having a composite interlayer comprising a layer of elastic foam and a layer made of =1 layer of 'Kevlar' (RTM-aromatic polyamide) fabric assembled from segments of fabric cut and tailored together edge to edge to obtain the hollow helmet from without any folds or wrinkles in the fabric. Pref. the fabric segments are cut using ultrasonic shears, to avoid any peripheral fraying, and are wetted with a binder resin to stabilise their shape and position. Pref. the shells are made of a rigid material which can deflect a bullet but which can be penetrated by a bullet without shattering, e.g. a self-extinguishing polyester resin with glass fibre reinforcement, opt. with a ceramic coating. The foam interlayer may be moulded to shape or may also be assembled from suitably tailored segments. Use of tailored segments minimises the quantity of expensive fabric and/or foam used per helmet.