IRSST - Institut de recherche Robert-Sauvé en santé et en sécurité du travail

Resistance of Protective Materials to Multiple Mechanical Stresses: Simultaneous Cutting and Puncturing


Lacerations of the puncture and cut type represent a significant proportion of hand injuries in many workplaces. There are a great variety of mechanical stressors, including points of blades, metal shards, poorly deburred components and shards of glass, and these constitute multiple risks. Wearing protective gloves helps reduce these risks. However, the gloves may not provide adequate resistance to all types of stresses. For example, since there is no correlation between resistance to cuts, punctures and pricking, a material may be highly resistant to one type of mechanical stressor, yet much less so to another type. Previous research conducted at the IRSST focused on the phenomena of cutting, puncturing and, more recently, pricking by medical needles. However, little is known about the mechanisms involved in puncturing by a pointed or sharp object. At present, the lack of information on the process combining puncturing and cutting, and the lack of objective characterization methods for this category of stressor, does not allow assessment of the protection provided by gloves against punctures or cuts.

The main objective of this study was to investigate fundamental aspects of the behaviour of protective materials against multiple mechanical stressors that cut and puncture simultaneously, with a view to developing an objective test method to characterize resistance to puncturing by a pointed and sharp object. To simulate a multiple mechanical stressor, experimental tests involving puncturing by pointed blades were carried out under different conditions. The effects of blade geometry (angle at the tip), material characteristics (thickness, type of material) and experiment conditions (including speed of movement, lubrication and angle of approach of the blade, as well as the pre-extension of the sample) on resistance to puncturing by a pointed blade were investigated in the elastomeric membrane. This research analyzed in detail the behaviour of the homogeneous materials most used in the manufacture of protective gloves, namely, neoprene rubber, butyl, nitrile, as well as a few models of protective gloves.

The results demonstrated that the mechanisms for puncturing the elastomeric membrane with pointed blades involved a mixed rupture mode, that is, combining Mode I (through normal stress to the crack/fissure plane) and Mode III (through shear stress parallel to the crack/fissure plane and the front of the crack/fissure. These mechanisms and the respective contributions of these rupture modes are different from those involved in puncturing by medical needles or by standardized probes rounded at the tip. The study also demonstrated the major contribution of friction between the blade and the material during the rupture process. The friction energy for the materials tested is two times higher than that required for the rupture. Consequently, the resistance of materials to puncturing by a pointed blade is greatly affected by the friction between the gloves employed and the mechanical stressor. This friction depends in particular on the working environment, whose operations may require, for example, the use of various lubricants.

The effects of the blade geometry, the material’s characteristics and the experiment conditions on resistance to puncture by a pointed blade were studied. Complete penetration force decreases as the angle of approach between the blade edge and the sample increases, as the blade is lubricated or as the material is extended. The complete penetration force, strongly dependent on the geometry of the blade and the thickness of the sample, does not represent an intrinsic parameter of the performance of the material at the puncture/cut.

A characterization method was therefore developed to allow an objective and quantitative assessment of the material's resistance to combined puncturing and cutting. It consisted in assessing the rupture and friction energies per unit area of the fissure created from a puncture test using a pointed blade. The results revealed that the rupture energy per unit area is independent of the geometries of the blade and the sample, thus representing an intrinsic property of the material and an objective parameter of the resistance to puncturing/cutting by pointed blades. The friction energy per unit area is also independent of the geometries of the blade and the sample, but varies with the surrounding environment. It plays an important role in material protection performance and can be considered a semi-intrinsic property that represents the conditions serving the puncture/cut. When the friction is high, it helps increase the resistance of the blade penetration into the material. That said, if there is a lubricant present in the environment, which helps to reduce the friction, then the use of high performance materials -- such as those with higher rupture energy per unit area (intrinsic parameter) -- should be considered to ensure a high level of protection.

This new approach to characterization was also tested on several types of protective gloves of different compositions and thicknesses. A simplified method, one that is faster and more feasible, is therefore being proposed for the characterization of protective gloves.

Additional Information

Category: Research Report
  • Ennouri Triki
  • Phuong Nguyen-Tri
  • Meriam Azaiez
  • Toan Vu-Khanh
  • Chantal Gauvin
Research Project: 0099-3770
Online since: April 12, 2016
Updated date: May 18, 2016
Format: Text