Bond strength test

Bond Strength Testing Service – Comprehensive Evaluation of Adhesive Performance for Structural, Industrial and Aerospace Applications

As an ISO/IEC 17025 accredited independent testing laboratory, we offer specialised bond strength testing services to manufacturers, engineering contractors, and quality assurance teams across the aerospace, automotive, construction, electronics, packaging, and medical device sectors. Bond strength – the maximum tensile, shear, peel, or cleavage stress that an adhesive joint can withstand before failure – is a critical performance parameter for products that rely on adhesives for structural integrity, sealing, or assembly. Our test protocols evaluate the strength of adhesive bonds under various loading modes, environmental conditions, and ageing regimes, providing essential data for material selection, process validation, product certification, and failure analysis. All methods are aligned with ISO, ASTM, EN, and GB/T standards, including ISO 4587 (Tensile lap-shear strength), ASTM D1002 (Tensile shear strength of adhesives), ASTM D5868 (Lap shear adhesion for fibre-reinforced plastics), ISO 14615 (Adhesives – Peel test), ASTM D1876 (T-peel test), EN 1465 (Lap shear test), GB/T 7124 (Tensile shear test), and GB/T 7122 (Peel test). Our inspection and test reports are recognised by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Industry and Information Technology (MIIT), and international certification bodies for product registration, type approval, and quality assurance.

Bond strength test

Adhesive Types and Bonded Assemblies We Regularly Test

Our bond strength test facilities accommodate a wide range of adhesive chemistries, substrate materials, and joint configurations. Typical test articles include:

Structural adhesives – epoxies, polyurethanes, acrylics, cyanoacrylates, and structural acrylic adhesives for load-bearing applications
Flexible adhesives and sealants – silicones, polyurethanes, and MS polymers for sealing and flexible bonding
Hot-melt adhesives – for packaging, woodworking, and assembly applications
Pressure-sensitive adhesives (PSAs) – tapes, labels, and films for temporary and permanent bonding
Composite bonding systems – for aerospace, automotive, and marine composites
Metal-to-metal, metal-to-polymer, and composite-to-composite assemblies
Coated and surface-treated substrates – with primers, anodised layers, or surface conversion coatings
Bonded joints subjected to environmental ageing – for assessing the durability of the adhesive bond

Tensile Shear Bond Strength Testing – Measuring the Strength of Lap Joints

Lap shear test – ISO 4587 / ASTM D1002 / GB/T 7124 – for metal-to-metal joints – We prepare standard lap shear specimens (typically 25 mm wide × 100-150 mm long, with a 12.5 mm or 25 mm overlap) by bonding two metal strips together with the adhesive. The specimens are cured under the specified conditions (temperature, pressure, and time). The joint is then pulled in tension in a universal testing machine at a controlled crosshead speed (typically 1.3 mm/min or 10 mm/min, depending on the standard). The maximum load (in N) and the lap shear strength (in MPa) are recorded. The failure mode is assessed by visual inspection.
Lap shear test for composites – ASTM D5868 / ISO 14615 – for fibre-reinforced plastics – We use a modified lap shear test method for composites, taking into account the specific characteristics of the composite substrates (e.g., surface roughness, fibre orientation). The test is performed at a specified crosshead speed, and the shear strength (in MPa) is calculated. The failure mode is also recorded.
Lap shear test at elevated or reduced temperatures – for simulating service conditions – We perform the lap shear test at specified temperatures (e.g., -40 °C, 80 °C, 150 °C) using a temperature-controlled chamber attached to the testing machine. The test determines the effect of temperature on the bond strength.
Lap shear after ageing – for assessing the durability of the adhesive bond – We condition the lap shear specimens in an environmental chamber (e.g., 40 °C, 95 % RH, 1 000 hours) or in a specific ageing medium (e.g., salt spray, acid rain, UV exposure) and then test the bond strength. The retention of the lap shear strength after ageing is calculated.

Peel Bond Strength Testing – Measuring the Resistance to Separation

T-peel test – ASTM D1876 / ISO 11339 / GB/T 7122 – for flexible-to-flexible and flexible-to-rigid joints – We prepare T-peel specimens by bonding two flexible strips (or one flexible and one rigid strip) together at one end. The free ends are placed in the grips of a universal testing machine and pulled apart at a specified crosshead speed (typically 50-300 mm/min). The peel force (in N/25 mm) is recorded. The average peel force and the peel resistance (in N/m or N/mm) are calculated.
180° peel test – ASTM D3330 / ISO 8510 / GB/T 2791 – for pressure-sensitive adhesives and flexible substrates – We apply a tape or a flexible adhesive layer to a rigid substrate (e.g., steel, glass) and peel it off at a 180° angle at a specified speed (typically 300 mm/min). The peel force (in N/25 mm) is recorded. The test is used to assess the adhesion of tapes, labels, and flexible adhesives.
90° peel test – ASTM D6862 / ISO 8510 / GB/T 2791 – for rigid-to-rigid and flexible-to-rigid joints – We perform a 90° peel test (with a 90° angle) on rigid-to-rigid or flexible-to-rigid joints. The peel force (in N/25 mm) is recorded. The 90° peel test is more severe than the 180° peel test and is used for high-performance adhesives.
Floating roller peel test – ASTM D3167 / ISO 4578 – for measuring the peel strength of metal-to-metal bonded joints – We use the floating roller peel test method, where the flexible bonded specimen is peeled off a rigid roller with a specified force and speed. The test is used for aerospace and automotive structural adhesives.

Tensile Bond Strength and Pull-Off Testing – Assessing the Resistance to Normal Stress

Tensile bond strength (pull-off) – ASTM D4541 / ISO 4624 / GB/T 5210 – for coatings and adhesives on rigid substrates – We use a portable pull-off adhesion tester to measure the force required to pull a bonded stud (a metal dolly) off the surface of the coated or bonded substrate. The test is performed at a specified loading rate (typically 0.1-1 MPa/s). The tensile bond strength (in MPa) is recorded, and the failure mode is assessed (cohesive, adhesive, or substrate failure).
Flat-wise tensile strength – ASTM C297 / ISO 8509 – for sandwich panels and thick adhesive joints – We apply a tensile load perpendicular to the plane of the bonded joint (flat-wise), using a universal testing machine. The test is used for assessing the tensile strength of thick adhesive joints and sandwich panels.
Butt joint tensile test – ISO 6922 / ASTM D2095 – for assessing the tensile strength of adhesives – We bond two cylindrical or rectangular specimens together with the adhesive and pull them in tension. The tensile strength (in MPa) is calculated from the maximum load and the bond area. The failure mode is recorded.

Shear and Cleavage Bond Strength Testing – Assessing Resistance to Shear and Peel Stresses

Cleavage test – ASTM D1062 / ISO 14615 – for assessing the resistance to splitting forces – We apply a tensile load to the free ends of a bonded joint, creating a cleavage (opening) force on the joint. The test is used for assessing the resistance of adhesives to peel and cleavage stresses.
Impact peel and impact shear test – for high-strain-rate applications – We perform impact peel and impact shear tests using a pendulum impact tester or a drop-weight tester. The test assesses the adhesion strength under high-strain-rate loading (e.g., during a crash or a drop).
Dynamic shear test – for assessing the shear strength under cyclic loading – We apply a cyclic shear load (sinusoidal or other waveform) to the bonded joint and measure the fatigue life. The test is used for assessing the shear fatigue resistance of structural adhesives.

Environmental and Durability Testing – Assessing the Long-Term Performance

Heat-ageing and thermal cycling – ASTM D4501 / ISO 9142 / GB/T 7124 – We condition the bonded joints at elevated temperatures (e.g., 70 °C, 100 °C, 150 °C) for a specified period (e.g., 168 hours, 1 000 hours) and then test the bond strength. The test is used to assess the thermal stability and the resistance to heat ageing.
Humidity and moisture ageing – ASTM D2247 / ISO 6270‑1 / GB/T 12000 – We condition the bonded joints in a humidity chamber (e.g., 40 °C, 95 % RH) for a specified period (e.g., 168 hours, 1 000 hours) and then test the bond strength. The test is used to assess the resistance to moisture ingress.
Salt spray and corrosion testing – ASTM B117 / ISO 9227 / GB/T 10125 – We expose the bonded joints to a salt spray environment (5 % NaCl, 35 °C) for 240-500 hours and then test the bond strength. The test is used to assess the resistance of the adhesive bond to corrosion and to corrosive environments.
UV and weathering – ASTM G154 / ISO 4892‑3 / GB/T 16422 – We expose the bonded joints to UV light (UVA-340 lamps, 0.89 W/m², 60 °C, 8h dry / 4h condensation cycles) for 500-2 000 hours and then test the bond strength. The test is used to assess the resistance to UV degradation and outdoor weathering.
Chemical resistance – ASTM D543 / ISO 175 / GB/T 11547 – We immerse the bonded joints in specified chemical solutions (e.g., oil, fuel, brake fluid, acid, alkali) for a specified period and then test the bond strength. The test is used to assess the resistance to chemical attack.

Failure Mode Analysis – Understanding the Mechanism of Failure

Visual and microscopic examination – for identifying the failure type – We inspect the fractured bonded joint to identify the failure mode: (a) cohesive failure – the failure occurs within the adhesive layer, indicating that the adhesive is the weakest part of the joint; (b) adhesive failure – the failure occurs at the adhesive-substrate interface, indicating poor adhesion; (c) substrate failure – the failure occurs in the substrate material, indicating that the adhesive is stronger than the substrate; (d) mixed failure – a combination of cohesive, adhesive, and substrate failure.
Fracture surface analysis – using stereomicroscopy and scanning electron microscopy (SEM) – ASTM E1508 / ISO 10543 – We examine the fracture surface under a stereomicroscope and, where required, under a scanning electron microscope (SEM) to identify the failure mechanism (e.g., micro-void coalescence, cleavage, or interfacial debonding).
Surface analysis – for identifying contamination or poor surface preparation – We analyse the surface of the substrate (before bonding) and the fracture surface (after the test) using energy-dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) to detect any contamination (oil, grease, dust) or poor surface preparation that may have contributed to the failure.

Regulatory Compliance and Product Certification – Supporting Industry Standards

Our bond strength testing services are performed in accordance with the most widely used international and national standards. The most commonly requested include:

ISO 4587 – Adhesives – Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies – the international standard for lap shear testing
ASTM D1002 – Standard Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading – the North American standard for lap shear testing
ASTM D5868 – Standard Test Method for Lap Shear Adhesion for Fiber Reinforced Plastic (FRP) Bonding – for FRP bonding
ISO 14615 – Adhesives – Determination of peel strength – the international standard for peel testing
ASTM D1876 – Standard Test Method for Peel Resistance of Adhesives (T-Peel Test) – for T-peel testing
ASTM D4541 – Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers – for pull-off testing
GB/T 7124 – Adhesives – Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies – the Chinese national standard for lap shear testing
GB/T 7122 – Adhesives – Determination of peel strength – the Chinese national standard for peel testing

Report Acceptance and Regulatory Recognition

All bond strength tests are conducted under our ISO/IEC 17025 accreditation, using calibrated universal testing machines, environmental chambers, and instrumentation, all traceable to national and international reference standards. Our final test reports include: a complete description of the test article (adhesive, substrate, surface preparation, cure conditions), the test method and conditions (temperature, humidity, crosshead speed), the measured parameters (lap shear strength, peel strength, tensile strength, failure mode), a statistical summary (mean, standard deviation, coefficient of variation), a detailed failure analysis (photographs and SEM images), and a clear pass/fail verdict against your specified acceptance criteria. These reports are accepted by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Industry and Information Technology (MIIT), and international certification bodies for product registration, type approval, and quality assurance. Bilingual (English/Chinese) versions are available to facilitate submissions to domestic and international authorities and to support your global market access.