Military Bulletproof Helmet Manufacturing Process - Primary Requirements

During the projectile penetrating textile-based materials, the strain propagates away from the impact point along the axis of yarn, simultaneously the strain also develops at opposite to the projectile flying direction to deflect the stress thus create the transverse wave velocity. From the strain wave propagating direction, it is cleared that the longer fibre, the better energy absorption. Thus, fibre continuity is desirable in reinforcements, it should be maintained throughout the whole manufacture without disturbance.

A flat fabric with continuous fibres conforming onto the arbitrary shape of surface was described as forming or draping. The preforms free of wrinkles/folding or misalignment serve as an ideal reinforcement for composite, achieving better energy absorption. Shearing is the major mechanism determining the draping behaviour, which can be predicted by bias extension and picture frame test. The mouldability tester was developed as an alternative as well.