Laminated Glass
Definition
Two glass sheets bonded with a polyvinyl butyral (PVB) interlayer. Cracks but does not shatter. Standard for windshields and bank counters. The PVB layer is itself a forensic substrate.
- Structure
- Two glass sheets bonded with PVB interlayer
- Fracture behaviour
- Cracks but does not shatter
- Common use
- Windshields, bank counters
- Forensic note
- PVB layer is itself a forensic substrate
Common questions
What can the PVB interlayer itself reveal in an examination?+
It can retain fibre, paint, or fingerprint traces transferred during an impact, and its stretching or tearing pattern can help reconstruct the direction and force of an impact separate from the glass fracture pattern.
Why does laminated glass matter for interpreting an impact event differently from ordinary annealed glass?+
Because the interlayer holds fragments together instead of letting them scatter, standard radial and concentric fracture-pattern analysis used on loose glass fragments applies differently, and the interlayer's own tear pattern becomes an additional source of directional evidence.
Related terms
- Borosilicate Glass
- Heat-resistant glass with about 80 percent SiO2 and 13 percent B2O3 (boric oxide). Low thermal expansion. Used in cookware (Borosil, Pyrex) and...
- Concentric Crack
- A crack that runs in roughly circular arcs around the point of impact, joining radial cracks. The 4C rule applies: Concentric cracks...
- Float (Pilkington) Glass
- Sheet glass manufactured on a bath of molten tin. The tin-contact face fluoresces under short-wave UV, which lets the analyst orient a...
- Radial Crack
- A crack that runs outward from the point of impact, like spokes of a wheel. The 3R rule applies: Radial cracks have...
- Soda-Lime Glass
- The commonest glass family. About 72 percent SiO2, 14 percent Na2O (from soda ash) and 10 percent CaO (from limestone), with small...
- Tempered Glass
- Glass heat-treated to introduce compressive surface stresses and tensile core stresses, producing a material four to five times stronger than annealed glass...
- Wallner Lines and Hackle Marks
- Wavy curved lines (Wallner) and step-like ridges (hackle) on a fracture surface that record the direction the crack front was moving. Used...