Puncture of elastomer membranes by medical needles. Part I: Mechanisms

Abstract

Resistance to puncture is a critical property for several applications, in particular for elastomer materials used in protective clothing. To evaluate the puncture resistance of membranes, some methods have been proposed as standard tests. However, the rounded puncture probes used in these tests are very different from real pointed objects like medical needles, and may not measure the level of material resistance that corresponds to them. In fact, puncture by medical needles is shown to proceed gradually as the needle cuts into the membrane. This behavior is highly different from puncture by rounded probes which occurs suddenly when the strain at the probe tip reaches the failure value. In addition, maximum force values are observed to be much smaller with medical needles. A method has been developed based on the change in strain energy with the puncture depth to evaluate the fracture energy associated to puncture. The results show that the phenomenon of puncture by medical needles involves contributions both from friction and fracture energy, in a similar way as for cutting. A lubricant was tentatively used to reduce the friction contribution for the computation of the material fracture energy.

Combined puncture/cutting of elastomer membranes by pointed blades: Characterization of mechanisms

“…The global fracture energy and the global friction energy, which are responsible of the creation for a new fracture surface in rubber materials, were measured by loading/unloading test at 100 mm/min (Figure ). These types of test are commonly used in several breaking methods to characterize the fracture energy . Rivlin and Thomas proposed this approach to calculate the tearing energy of rubbers .…”

“…This approach was also used to study the tearing energy of textile materials by trouser tear tests and tensile tests . Others studies have characterized the puncture and cutting of rubber by loading/unloading tests …”

“…The puncture tests by a rounded probe showed that the penetration force largely depends on the deformation of elastomer membranes . However, in the case of puncture by medical needles, the material deformation is low. A linear relationship between the penetration force and probe (medical needles and conical and rounded probes) diameter is observed…”

Airtight container for the transfer of atmosphere-sensitive materials into vacuum-operated characterization instruments

“…The present device has been specifically designed to meet the conditions for single crack propagation and where a single nucleation site is promoted by puncture, the elastomer is not too brittle, the strain-rate during the crack opening is small and the tension of the membrane is anisotropic. 7 (4), and the needle (5). For better visibility, the two side braces, which maintain the upper ring in compression over the membrane, are not shown on these schematics.…”

Combined puncture and cutting of elastomer membranes: A fracture energy approach

“…The intrinsic material properties controlling the puncture/cutting process are also still unknown, which limits the ability to produce gloves to protect against punctures and cuts. However, the resistance of elastomer membranes to mechanical hazards such as cuts and punctures has been widely studied . The resistance to punctures or cuts is usually assessed using applied force.…”