Testing Kevlar Material and Stab-Proof Vests

Solution

• Twin-column, software-controlled tensile/compression test system.
• Load cells were selected to match the required test forces.
• Adjustable upper grip to hold a range of blade- or spike-like implements.
• Lower fixture table designed to support vest samples securely..

Benefits

• Flexible software environment to calculate key performance parameters.
• Large test space accommodating a variety of vest sizes and designs.
• Reliable, repeatable testing to provide confidence in wearer protection.

Requirement

Kevlar® is one of the strongest materials available and is used in protective gloves, tires, and even bulletproof vests. The material's strength-to-weight ratio makes it the material of choice for stab-proof vests that combine Kevlar inserts with external layers of softer material for comfort.

These need to withstand stabbings from knives, spikes, and other sharp, pointed items while allowing easy movement. A leading law enforcement agency required comparative testing of new and used vests to measure penetration resistance across different areas, including shoulders, chest, sides, and back, using real-world knives and improvised weapons.

Solution

The protective performance of Kevlar® arises from its tightly woven fibers. Under a stabbing impact, the weave absorbs energy and slows the entry of a sharp object.

Pointed weapons may separate fibers locally, while broader blades can be caught in the weave, reducing the likelihood of complete puncture.

Presto Stantest supplied a MultiTest 25-i twin-column tensile tester fitted with a special upper fixture to hold a variety of knife blades and improvised stabbing implements. A lower penetration jig securely positions vest specimens, allowing the blade to pass through safely. Emperor™ software controlled the test, applying compressive forces while recording maximum penetration force in newtons and the energy absorbed in joules, providing critical comparative performance data.

Test equipment

• The MultiTest 25-i is a twin-column, software-controlled tensile/compression test system.
• 10 kN cell
• Adjustable upper grip for knives and improvised stabbing tools.
• Lower support fixture with an aperture to allow complete penetration.