Axial tensile breaking force testing measures the maximum longitudinal pull force that a medical catheter shaft or its bonded joints can withstand before rupturing or separating. This critical mechanical performance evaluation, specified in standards such as ISO 10555-1, YY/T 0285.1, ASTM F623, and EN 1616, is essential for design verification, manufacturing quality control, and regulatory submission of catheter-based medical devices. Accredited third-party laboratories routinely perform this testing to reduce the risk of in-vivo catheter fracture and to safeguard patient safety.
Technical Overview
Axial tensile breaking force testing is a destructive mechanical test in which a catheter specimen is clamped at both ends and loaded in tension along its longitudinal axis until the shaft, joint, or hub interface fractures or separates. The peak force recorded at the moment of failure is defined as the axial breaking force (also referred to as rupture force or tensile strength of the catheter assembly).
This test is clinically significant because catheters are subjected to substantial axial stresses during insertion, manipulation, exchange, and inadvertent traction in use. If the shaft or a bonded junction fails in vivo, the consequences can include catheter fragmentation, distal embolization, fluid leakage, and difficult surgical retrieval. Regulatory bodies and product standards therefore treat breaking force as a fundamental safety performance requirement for catheter-type devices.
The primary standards governing this test include:
- ISO 10555-1: Sterile and single-use intravascular catheters — Part 1: General requirements, which defines tensile strength requirements for the catheter body and all component joints, with minimum force values scaled to the catheter's outside diameter.
- ISO 10555-3, ISO 10555-4, and ISO 10555-5: Requirements for central venous catheters, balloon dilatation catheters, and over-needle peripheral catheters, all referencing the general test method.
- ISO 11070: Sterile single-use intravascular catheter introducers, including sheath and dilator tensile integrity.
- YY/T 0285.1: The Chinese medical industry standard for intravascular catheters, aligned with ISO 10555-1.
- GB/T 15812.1: Chinese national standard for non-vascular medical catheters, covering general performance including connection strength.
- ASTM F623: Standard specification for Foley (indwelling urinary) catheters, including strength requirements.
- EN 1616 and ISO 20696: Requirements for sterile single-use urinary and intermittent urethral catheters, including connection strength.
Testing is typically performed on a calibrated universal tensile testing machine equipped with an appropriately sized load cell and specialized clamping fixtures that grip the delicate polymer tubing without causing premature slippage or jaw-edge failure.
Testing Samples
Intravascular Catheters
This category includes peripheral intravenous catheters, central venous catheters (CVC), peripherally inserted central catheters (PICC), balloon dilatation catheters, neurovascular microcatheters, hemodialysis catheters, and introducer sheaths with dilators. Both the shaft tubing and the complete catheter assembly, including hub-to-shaft joints, are evaluated.
Non-Vascular Catheters
This category covers urinary (Foley) catheters, intermittent urethral catheters, gastrointestinal feeding tubes, drainage catheters, epidural catheters, and various surgical suction and irrigation catheters. For these products, the strength of the shaft, the balloon bonding region, and the funnel or connector interface is of particular interest.
Catheter Components and Joints
In addition to finished devices, individual components and junctions may be tested in isolation, including:
- Hub-to-tube bond points and solvent or UV-cured adhesive joints
- Thermal weld seams and RF-welded side arms
- Y-site, bifurcation, and reinforcement sleeve junctions
- Soft distal tip-to-shaft transitions and marker band regions
- Luers and other molded connector interfaces
Specimen Conditioning and Quantity
Specimens are conditioned in a standard laboratory atmosphere, typically 23 °C ± 2 °C and 50 % ± 10 % relative humidity per ISO 291, for the equilibration period defined by the applicable product standard. Testing is normally conducted on finished, sterilized product in its final packaged condition when the objective is release or regulatory verification. A minimum of three to five specimens per lot is typical, or the number required by the product standard or the manufacturer's statistical sampling plan.
Testing Items
Depending on the product family and applicable standard, the following items are commonly evaluated:
- Axial breaking force of the catheter shaft (tube rupture force)
- Joint separation force between the hub and catheter tubing
- Bond strength of welded, glued, or fused junctions along the catheter body
- Strength of side arms, Y-ports, and bifurcation connections
- Securement strength of tip segments and sleeve reinforcements
- Elongation at break and force-displacement behavior (supplementary data)
- Failure mode classification, such as shaft rupture, joint separation, or hub fracture
Testing Methods
Test Principle
The specimen is secured between two axially aligned grips of a universal testing machine. A steadily increasing tensile load is applied along the catheter axis at a constant crosshead separation rate until the specimen fails. The maximum force achieved prior to failure is recorded as the axial breaking force, and the location and mode of failure are documented.
Apparatus and Calibration
The test system comprises a universal tensile testing machine with:
- A load cell of suitable capacity, typically offering resolution of 0.01 N to 0.1 N for small-bore catheters, verified in accordance with ISO 7500-1 or ASTM E4
- Pneumatic, mechanical wedge, or custom cushioned grips that apply uniform pressure without cutting or crushing thin-walled polymer tubing
- A data acquisition system capturing force and displacement at sufficient sampling frequency to reliably detect the true peak force
- A gauge length and crosshead speed set according to the applicable product standard, with speeds commonly specified in the range of tens to hundreds of millimeters per minute depending on the standard and product family
Specimen Preparation
Specimens are removed from their packaging with care to avoid pre-stressing. The outside diameter of the tubing is measured and recorded, because minimum acceptance forces in standards such as ISO 10555-1 are tiered by the largest outside diameter of the catheter or component. Where the complete assembly is tested, the hub is mounted in a suitable fixture so that the load path passes through the hub-to-tube joint exactly as it would in clinical use.
Test Procedure
- Condition the specimens as specified and verify ambient laboratory conditions
- Mount the specimen in the aligned grips with the specified gauge length and apply a small preload to remove slack
- Apply the tensile load at the constant separation rate defined by the applicable standard
- Continue loading until the specimen ruptures or separates, recording the peak force and the force-displacement curve
- Document the exact failure location and failure mode for each specimen
- Repeat the test for the required number of replicate specimens and calculate individual and mean values as required
Data Evaluation and Acceptance Criteria
Results are compared against the minimum force requirements of the applicable product standard. Under ISO 10555-1 and YY/T 0285.1, the required minimum breaking force increases with the catheter's outside diameter: small-bore neurovascular or peripheral catheters must meet forces of only a few newtons, while large-bore hemodialysis and introducer-type catheters must withstand substantially higher loads. All components and joints of the assembly must satisfy the criterion, and failure must occur in the tubing or joint rather than through grip-induced cutting. Manufacturers may also define internal acceptance limits stricter than the standard for process control purposes.
Test Report
A complete report typically includes specimen identification and dimensions, sterilization and packaging status, conditioning details, test machine configuration with load cell capacity, gauge length and crosshead speed, individual and mean breaking force values, failure mode and location for each specimen, pass or fail judgment against the specified criteria, and any deviations from the standard method.
Applications
Axial tensile breaking force testing supports the full lifecycle of catheter-based medical devices:
- Design verification and validation: demonstrating that new catheter designs and design changes meet standardized and risk-based strength requirements prior to regulatory submission
- Process development and validation: confirming window robustness for thermal welding, solvent bonding, UV curing, tipping, and hub assembly operations
- Incoming quality control: evaluating extruded tubing lots from suppliers for consistent mechanical strength
- Routine batch release: verifying production consistency as part of finished product acceptance testing
- Regulatory submissions: generating objective evidence for product registrations and technical documentation in major markets, including NMPA, FDA, and EU MDR dossiers
- Stability and aging studies: confirming that breaking force is maintained after sterilization, real-time storage, and accelerated aging
- Failure analysis: investigating field complaints, returned fractured catheters, and process deviations to identify root causes such as under-cured adhesive, excessive rework, or material degradation
Testing performed by accredited third-party laboratories provides manufacturers with impartial, standards-compliant data that strengthens both internal quality decisions and external regulatory filings.
FAQ
What is the difference between catheter shaft breaking force and joint separation force?
Shaft breaking force is the force required to rupture the catheter tubing itself, whereas joint separation force is the force required to pull apart a connection such as a hub-to-tube bond or a welded side arm. Standards such as ISO 10555-1 require every load-bearing element of the catheter assembly to satisfy the applicable minimum, so both failure types must be assessed.
How many specimens should be tested?
Most product standards and internal protocols specify a minimum of three to five specimens per lot or per production run, though the exact number depends on the applicable standard, the purpose of the study (screening versus release testing), and the statistical rationale defined by the manufacturer.
What happens if the specimen slips in the grips before breaking?
Slippage invalidates the result. Laboratories mitigate this by using pneumatic grips with controlled pressure, cushioned or conformable jaw faces, increased grip length, gentle specimen wrapping, or specially machined fixtures. A valid failure must occur in the specimen body or joint, not at the jaw line, unless the standard explicitly evaluates a joint located at that position.
Can testing be performed on sterilized finished products?
Yes, and it is strongly recommended. Sterilization processes such as ethylene oxide exposure and gamma or e-beam irradiation can affect polymer mechanical properties, so verification of breaking force on the product in its final sterilized condition provides the most clinically relevant evidence.
What failure modes are recorded during testing?
Typical documented failure modes include ductile rupture of the tubing, brittle fracture, debonding at adhesive or weld interfaces, separation of the hub from the shaft, and fracture of molded connector components. Recording the failure location for every specimen is essential for interpreting results and driving corrective actions.
How does catheter size affect the acceptance criterion?
Standards tier the minimum required force by the largest outside diameter of the catheter or component. Larger-diameter catheters must withstand greater forces because they are generally used in higher-flow, higher-load clinical applications, whereas microcatheters are assessed against correspondingly lower thresholds.