The main requirements of any Impact or Bullet Resistance Glass (BRG) structure are related to their impact strength properties (performance), their optical properties (functionality) and the mechanical consistency of the laminates (linked to their operational life span). 
This ArtiBlog focuses our attention around the factors that influence the mechanical consistency of laminates with the aim to know how to increase the present durability of the laminates.
The delamination is the most important problem of any laminated structure and one of the main failure causes. Delaminations might come from: limitations or defects on anyone of the laminated materials, process lamination conditions or failures or/and environmental materials changes during their operational life that might affect the laminates resistance.
From all laminated layers, the PVBs or TPUs are the main ones used to join all the others (glasses, PCs, PMMAs, PETs). Until now the TPUs used for the Ballistic Resistant Glass (BRG) constructions have been supplied just like optical and adhesive films. Most of the TPU grades available in the market are manufactured with just these two basic properties on them and with poor mechanical properties on them (see our previous report The Mechanical Behavior of TPUs used for BRG structures).
All TPUs have good elastic properties but most of them lack of the structural properties needed to insure the mechanical consistency of the laminates under real ambient conditions. With all the other quality parameters under spec, this is the critical factor that can reduce the operational life spans of the laminates. To extend the life of the laminates over 3 years something else needs to be changed and done also. Our TPU Grades we developed and manufacture, take this need into account.
To go deeper to this subject, we recommend you to download and go through our 10 pages Report.