Automotive wire harness insulation abrasion resistance testing measures the ability of cable insulation to withstand repeated mechanical scraping until the conductor is exposed, making it one of the most important durability gates for vehicle electrical systems. Conducted by accredited third-party laboratories in accordance with ISO 6722-1, ISO 14572, GB/T 25085, and related standards, the scrape abrasion test helps wire manufacturers, harness suppliers, and OEMs prevent chafing-induced short circuits and vehicle fires.
Technical Overview
Automotive wire harness insulation abrasion resistance testing, commonly known as the scrape abrasion test, is a laboratory mechanical durability test that evaluates how well the insulation of an automotive wire or cable resists repeated reciprocating scraping action. The test replicates real-world chafing conditions in which a harness rubs against sheet-metal edges, brackets, clamps, grommets, or adjacent harnesses while the vehicle is in motion. During the test, a hardened stylus or needle is pressed against the insulation under a defined load and moved back and forth until the insulation is worn through and electrical contact with the conductor is detected.
This test is critical because modern vehicles contain kilometers of wiring routed through tight, often abrasive environments. Engine compartments, chassis cross-members, door hinges, and seat mechanisms all subject harnesses to continuous vibration-induced relative motion. If the insulation wears through, the consequences range from intermittent signal faults and blown fuses to corrosion, loss of propulsion or braking control functions, and, in the worst case, thermal events and fire. The scrape abrasion test therefore quantifies the safety margin of an insulation system before it is released for series production.
The principal standards governing this test include ISO 6722-1 for 60 V single-core road vehicle cables, ISO 14572 for 600 V and higher-rated cables used in conventional and electrified vehicles, and GB/T 25085, the Chinese national adoption of the ISO 6722 series. Complementary material-level methods such as ASTM D2197 (scrape abrasion) and ASTM D4060 (rotary platform abrasion), along with UL and JIS cable test methods, are used for comparative evaluation of insulation compounds, tapes, and protective sleeving.
Results are typically expressed as the number of scrape cycles sustained before conductor contact occurs, as a pass/fail verdict against a minimum cycle count defined for the insulation class, or as the residual dielectric withstand capability of the abraded specimen.
Testing Samples
Single-Core Insulated Low-Voltage Wires
These are the most common test objects and include copper or tinned-copper conductors with cross-sections typically ranging from 0.35 mm² to 6 mm², insulated with PVC, cross-linked PVC, XLPE, TPE, or TPU compounds. Standard-wall, thin-wall, and ultra-thin-wall constructions are all evaluated, and the applied scraping load and acceptance threshold are selected according to the wall class. Specimens are generally supplied as straight lengths of approximately 0.5 m to 1 m, with three to five samples tested per condition to account for material variability.
High-Voltage Cables for Electric Vehicles
Electric and hybrid vehicles use shielded high-voltage cables with large cross-sections, commonly 25 mm² to 95 mm², rated at 600 V or higher and insulated with XLPO, silicone, or specially formulated elastomers. Because these cables are heavier and often routed through metal battery enclosures and underbody brackets where relative movement is significant, ISO 14572 and vehicle-maker specifications impose demanding abrasion requirements on both the insulation and the outer sheath.
Protected Harness Segments and Covering Materials
System-level specimens consisting of wires wrapped with PVC or PET tape, enclosed in corrugated conduit, or covered with braided sleeving can be tested to assess the contribution of the protection system as a whole. Flat material coupons of tapes, sleeves, and sheath compounds are also submitted for comparative rotary or linear abrasion testing when screening new materials.
Testing Items
The scope of insulation abrasion testing typically covers the following items, with the exact parameters defined by the applicable product standard:
- Reciprocating scrape abrasion resistance, reported as the number of cycles to insulation breakthrough
- Pass/fail abrasion resistance at a specified load and minimum cycle count for the insulation class
- Abrasion testing at elevated temperature or after thermal aging, where required by the specification
- Dielectric withstand verification performed on the abraded specimen
- Insulation resistance measurement after abrasion exposure
- Visual and photographic assessment of wear-through, cracking, smearing, or melting of the insulation
- Comparative rotary (Taber-type, ASTM D4060) or linear sandpaper abrasion for tapes, sleeves, and sheath materials
Testing Methods
The core procedure is the reciprocating scrape test defined in ISO 6722-1, ISO 14572, and GB/T 25085. The apparatus consists of a rigid fixture that holds the wire specimen taut, a hardened steel needle or stylus of standardized geometry mounted on a reciprocating carriage, a dead-weight or pneumatic loading system that presses the stylus against the insulation with a calibrated force, and an electrical detection circuit. The conductor is connected to the detection circuit, and the moment the stylus penetrates the insulation and touches the conductor, the circuit trips, the machine stops, and the cycle counter registers the failure point.
Specimen Preparation and Conditioning
Specimens are cut to the required length, and the conductor ends are exposed for electrical connection. Samples are conditioned in a standard laboratory atmosphere, typically 23 °C ± 5 °C, for a defined stabilization period before testing. Where the specification requires it, specimens may be pre-conditioned by heat aging or tested inside an environmental chamber at elevated temperature to evaluate retained abrasion performance after thermal exposure.
Scrape Abrasion Test Procedure
- Mount the specimen securely in the fixture so that the insulated section is supported without slack or pre-deformation.
- Select the scraping load, stroke length, and stroke rate according to the cable size and insulation wall class specified in the standard; stroke rates on the order of 50 to 60 double strokes per minute are typical.
- Connect the conductor to the failure-detection circuit and verify the trip function.
- Start the reciprocating scraping action and allow it to continue until the detection circuit indicates conductor contact.
- Record the number of cycles to breakthrough, then repeat the test on the remaining specimens.
- Report individual results, the mean or minimum value as required, and any anomalous wear morphology observed.
Post-Abrasion Electrical Verification
When the specification calls for verification on specimens that have survived the required number of cycles, a dielectric withstand voltage is applied between the conductor and an electrode in contact with the abraded region, and insulation resistance is measured. The specimen must withstand the specified voltage without breakdown and maintain the minimum insulation resistance defined by the standard.
Acceptance Criteria
Acceptance is defined in the product standard or customer drawing and is typically expressed as a minimum number of scrape cycles without breakthrough for a given load, wall class, and conductor size. High-voltage cables and cables intended for severe routing environments generally carry higher minimum cycle requirements than standard low-voltage cabin wiring.
Applications
Insulation abrasion resistance testing is applied throughout the automotive electrical supply chain and supports product development, qualification, and failure analysis:
- Type approval and design validation of new cable designs before series release by wire and cable manufacturers
- Incoming inspection and supplier qualification programs at harness assembly plants
- Validation of high-voltage EV cable systems routed through battery enclosures, underbody structures, and metal brackets
- Material research and screening of PVC, XLPE, TPE, TPU, and silicone insulation compounds
- Production part approval and periodic quality audits demonstrating continuing compliance with ISO 6722-1, ISO 14572, or GB/T 25085
- Root-cause investigation of field failures involving harness chafing, intermittent faults, or electrical short circuits
- Benchmarking of alternative protection systems such as textile sleeving, tapes, and corrugated conduit
Test reports from accredited third-party laboratories are widely used as objective evidence in customer submissions, homologation packages, and dispute resolution between supply-chain partners.
FAQ
What counts as failure in the scrape abrasion test?
Failure is defined as the first moment the scraping stylus penetrates the insulation and makes electrical contact with the conductor, which is detected automatically by the trip circuit. The number of cycles completed up to that point is the abrasion resistance result for that specimen.
Which standards govern automotive insulation abrasion testing?
The primary standards are ISO 6722-1 for 60 V single-core cables, ISO 14572 for 600 V and high-voltage cables, and GB/T 25085 as the Chinese national adoption of the ISO 6722 series. UL and JIS cable test methods, as well as ASTM abrasion methods such as ASTM D2197 and ASTM D4060, are used for complementary or material-level evaluations.
How many specimens are required and how long does testing take?
Most test plans require three to five specimens per condition to obtain a statistically meaningful result. A single scrape test typically runs from several minutes to a few hours depending on the required cycle count, and complete programs including conditioning and reporting are usually completed within a few working days.
Can the test be performed at elevated temperature?
Yes. Where the product specification requires it, specimens can be tested inside a temperature-controlled chamber or after prior heat aging to determine whether the insulation retains its abrasion resistance under thermal stress, which is particularly relevant for engine-bay and battery-compartment applications.
How does scrape abrasion differ from other mechanical abuse tests?
The scrape test isolates progressive surface wear caused by repeated rubbing, whereas crush, impact, and notch tests evaluate resistance to single-event mechanical damage. Both categories are needed for a complete assessment of harness mechanical durability, but abrasion resistance is the parameter most directly linked to long-term chafing behavior in service.
What information should be provided when commissioning a test?
The client should supply the cable or harness samples, the applicable standard or customer specification, the insulation wall class, the conductor size, the required scraping load, and the acceptance criterion. Accredited third-party laboratories can also assist in selecting appropriate test parameters when a specification reference is incomplete.