Glass Fibre Reinforced Plastic (GFRP) Parts and Threaded Sealant Performance Testing Service – Comprehensive Evaluation of Structural Integrity, Sealing Efficiency and Long‑Term Durability
As an ISO/IEC 17025 accredited independent testing laboratory, we offer specialised testing services for glass fibre reinforced plastic (GFRP) components and threaded sealant systems used across the automotive, aerospace, marine, construction, chemical processing, and general industrial sectors. GFRP parts – commonly known as fibreglass – are lightweight, high‑strength composites widely used for structural and corrosion‑resistant applications, while threaded sealants are critical for preventing leakage and ensuring the integrity of bolted connections. Our test protocols evaluate the mechanical performance, thermal stability, chemical resistance, and environmental durability of GFRP parts, as well as the sealing capability, adhesion, and long‑term reliability of threaded sealants under simulated service conditions. All methods are aligned with ISO, ASTM, EN, and GB/T standards, including ISO 527 (Tensile properties of plastics), ASTM D790 (Flexural properties of plastics), ISO 14125 (Fibre‑reinforced plastic composites – Flexural properties), ASTM D638 (Tensile properties of plastics), ISO 10952 (Plastics piping systems – Glass‑reinforced thermosetting plastics – Determination of the resistance to chemical attack), ASTM D5365 (Sealant performance), ISO 898‑1 (Mechanical properties of fasteners), and GB/T 1040 (Plastics – Determination of tensile properties). 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.
GFRP Parts and Sealant Systems We Regularly Test
Our testing facilities accommodate a wide range of GFRP components and threaded sealant products. Typical test articles include:
- GFRP structural components – beams, channels, angles, rods, tubes, and custom‑moulded parts for construction, infrastructure, and industrial equipment
- Pultruded GFRP profiles – for bridge decks, walkways, handrails, and ladders
- Filament‑wound GFRP pipes and vessels – for chemical processing, water treatment, and oil and gas applications
- Sheet moulding compounds (SMC) and bulk moulding compounds (BMC) – for automotive body panels, electrical enclosures, and consumer goods
- Hand lay‑up and spray‑up GFRP parts – for marine hulls, tanks, and custom fabrications
- Threaded sealants and adhesives – anaerobic sealants, PTFE‑based sealants, threadlockers, and pipe joint compounds
- Bolted connections with GFRP components – for assessing the sealing and load‑bearing performance of the entire assembly
- Coated and surface‑treated GFRP parts – with protective gelcoats, paints, or anti‑corrosion coatings
Mechanical Properties Testing – Tensile, Flexural and Compressive Performance of GFRP
- Tensile strength and modulus – ISO 527 / ASTM D638 / GB/T 1040 – We test standard GFRP specimens (dumbbell‑shaped or straight‑sided) in a universal testing machine at a crosshead speed of 2‑10 mm/min, depending on the material and the standard. The tensile strength (in MPa), the tensile modulus (in GPa), and the elongation at break (in %) are recorded. For pultruded GFRP, the tensile strength is typically in the range of 150‑300 MPa; for SMC and BMC, it is typically 50‑150 MPa. The results are compared to the specified minimum values for the material grade.
- Flexural strength and modulus – ISO 14125 / ASTM D790 / GB/T 1449 – We perform three‑point or four‑point bending tests on GFRP specimens (typically 80 mm × 10 mm × 4 mm) at a crosshead speed of 1‑2 mm/min. The flexural strength (in MPa) and the flexural modulus (in GPa) are recorded. For high‑performance GFRP, the flexural strength can exceed 300 MPa. The test is performed at room temperature (or at the specified temperature).
- Compressive strength – ISO 14126 / ASTM D695 / GB/T 1448 – We test cylindrical or prismatic GFRP specimens in compression, recording the compressive strength (in MPa) and the compressive modulus (in GPa). The compressive strength is typically lower than the tensile strength for most GFRP materials.
- Shear strength – ASTM D5379 / ISO 14129 / GB/T 1450 – For assessing the interlaminar shear strength of GFRP laminates, we perform a short‑beam shear test (three‑point bending with a short span) and record the apparent shear strength (in MPa). This test is essential for evaluating the quality of the fibre‑matrix bond.
- Impact resistance – ISO 179 / ASTM D256 / GB/T 1843 – We perform Charpy and Izod impact tests on notched and un‑notched GFRP specimens to evaluate the toughness and the resistance to brittle fracture. The impact strength is expressed in kJ/m² or J/m.
Thermal and Environmental Durability Testing – Resistance to Heat, Moisture and Chemicals
- Heat deflection temperature (HDT) – ISO 75 / ASTM D648 / GB/T 1634 – We determine the temperature at which a GFRP specimen deflects by a specified amount under a specified bending load (1.82 MPa or 0.45 MPa). The HDT is a measure of the material's resistance to deformation at elevated temperatures. For GFRP, the HDT is typically 100‑200 °C, depending on the resin system.
- Water absorption and moisture resistance – ISO 62 / ASTM D570 / GB/T 1034 – We immerse GFRP specimens in water at 23 °C (or at 70 °C) for a specified period (typically 24 hours, 7 days, or 28 days) and measure the weight gain (in %). A high water absorption (> 1 %) indicates a porous or low‑quality material that may degrade in humid environments.
- Chemical resistance – ISO 10952 / ASTM D543 / GB/T 11547 – We immerse GFRP specimens in a specified chemical solution (e.g., 10 % H₂SO₄, 10 % NaOH, 5 % NaCl, or organic solvents) at a specified temperature (e.g., 23 °C, 60 °C) for a specified period (typically 7‑28 days) and evaluate the changes in weight, dimensions, and mechanical properties (tensile and flexural strength). The chemical resistance is critical for GFRP used in chemical process equipment, storage tanks, and pipe systems.
- UV weathering and accelerated ageing – ASTM G154 / ISO 4892‑3 / GB/T 16422 – We expose GFRP specimens to UVA‑340 or xenon‑arc lamps for 500‑2 000 hours to simulate the effects of sunlight and outdoor weathering. After exposure, we measure the colour change (ΔE*), the gloss retention, and the retention of tensile and flexural strength. A strength retention of ≥ 80 % after 1 000 hours is typically required for outdoor applications.
- Thermal cycling and thermal shock – IEC 60068‑2‑14 / GB/T 2423.22 – We subject GFRP assemblies to 50‑100 thermal cycles between -40 °C and +80 °C (or between -20 °C and +100 °C) to assess the resistance to cracking and delamination caused by differential thermal expansion of the glass fibres and the resin matrix.
Threaded Sealant Performance Testing – Sealing Capability, Adhesion and Durability
- Sealing performance test – ASTM D5365 / ISO 898‑1 / GB/T 16823 – We assemble a threaded connection (bolt and nut, or pipe fitting) with the specified sealant applied to the threads. The assembly is pressurised (hydrostatically or pneumatically) to a specified pressure (typically 1‑10 MPa) and held for a specified period (typically 1‑24 hours). The pressure drop (or the presence of leakage) is monitored and recorded. A sealant that provides a leak‑tight seal under the specified pressure is considered effective.
- Breakaway torque and prevailing torque – for assessing the friction and locking performance – We measure the breakaway torque (the torque required to start loosening the fastener) and the prevailing torque (the torque required to rotate the fastener after the initial breakaway) using a calibrated torque wrench or a torque‑angle tester. The test is performed on a thread assembly with and without the sealant, and the results are compared to the specified requirements.
- Adhesion strength of the sealant – ASTM D1002 / ISO 4587 / GB/T 7124 – We apply the sealant to a standard test coupon (or to a threaded fastener) and measure the tensile shear strength (in MPa) using a universal testing machine. The adhesion strength is a measure of the sealant's ability to bond to the metal surface.
- Chemical resistance of the sealant – ASTM D543 / ISO 175 / GB/T 11547 – We immerse the sealant‑coated fastener in a specified chemical solution (e.g., oil, fuel, brake fluid, or acid) for a specified period and then test the sealing performance and the adhesion strength. A good sealant must retain its sealing properties after exposure to the service fluids.
- Temperature resistance of the sealant – ASTM D573 / ISO 188 / GB/T 3512 – We condition the sealant‑coated fastener at a specified temperature (e.g., 100 °C, 150 °C) for a specified period (e.g., 24‑168 hours) and then test the sealing performance and the breakaway torque. The test assesses the sealant's ability to withstand elevated temperatures without degradation.
Combined Performance Testing – GFRP Parts with Threaded Connections
- Pre‑load relaxation and creep – for GFRP‑to‑metal connections with sealants – We assemble a GFRP component to a metal component using a threaded fastener (with the specified sealant) and apply a controlled pre‑load (torque or tension). We measure the relaxation of the pre‑load over time (up to 1 000 hours) by monitoring the torque or the tension. A high relaxation (> 20 %) indicates a potential loss of joint integrity.
- Corrosion testing – for GFRP‑to‑metal interfaces with sealants – ASTM B117 / ISO 9227 / GB/T 10125 – We assemble a GFRP component and a metal component (with the sealant applied to the threads) and expose the assembly to a salt spray environment (5 % NaCl, 35 °C) for 240‑500 hours. After the test, we inspect the assembly for any signs of corrosion of the metal, any degradation of the GFRP, and any loss of sealing integrity.
- Vibration and fatigue testing – for GFRP bolted joints – ISO 16750‑3 / IEC 60068‑2‑6 – We subject a bolted GFRP assembly to a defined vibration profile (sinusoidal or random) for a specified duration (1‑10 hours). We monitor the torque retention and the sealing performance during and after the vibration test. The test assesses the ability of the sealant and the threaded connection to maintain integrity under dynamic loading.
- Thermal cycling of GFRP‑to‑metal connections – for assessing the effect of differential thermal expansion – We subject the GFRP‑metal assembly to 10‑50 thermal cycles between -40 °C and +80 °C, and then test the sealing performance and the torque retention. The test assesses the risk of leakage or loosening caused by differential thermal expansion of the GFRP and the metal.
Quality Control and Material Characterisation – Ensuring Consistency and Compliance
- Fibre content and void content – ASTM D3171 / ISO 1172 / GB/T 2577 – We determine the glass fibre content (in %) and the void content (in %) of GFRP specimens using the ignition loss method (burning off the resin) or the acid digestion method. A high fibre content (> 50 %) and a low void content (< 3 %) indicate a high‑quality composite.
- Resin cure and glass transition temperature (Tg) – DSC – ISO 11357 / ASTM E1356 – We use differential scanning calorimetry (DSC) to determine the degree of cure and the glass transition temperature (Tg) of the resin matrix. A high degree of cure (> 95 %) and a Tg above the service temperature are required for long‑term durability.
- Degree of cure of the sealant – for assessing the curing behaviour of anaerobic and reactive sealants – We use DSC or FTIR to measure the degree of cure of the sealant after the specified curing time and temperature. An insufficient degree of cure (< 80 %) indicates that the sealant may not develop its full sealing and adhesion properties.
- Microscopic examination – for assessing fibre distribution and defects – ASTM E3 / ISO 4496 – We prepare metallographic sections of GFRP specimens and examine the fibre distribution, the presence of voids, and the quality of the fibre‑resin interface using an optical microscope (50‑200×).
Regulatory Compliance and Product Certification – Supporting Industry Standards
Our testing services for GFRP parts and threaded sealants are performed in accordance with a wide range of national and international standards. The most commonly requested include:
- ISO 527 – Plastics – Determination of tensile properties – for tensile testing of GFRP
- ASTM D790 – Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics – for flexural testing
- ISO 14125 – Fibre‑reinforced plastic composites – Determination of flexural properties – for flexural testing of composites
- ISO 10952 – Plastics piping systems – Glass‑reinforced thermosetting plastics – Determination of the resistance to chemical attack – for chemical resistance testing
- ASTM D5365 – Standard Test Method for Long‑Term Ring‑Bending Strain of “Fiberglass” (Glass‑Fiber‑Reinforced Thermosetting‑Resin) Pipe – for pipe testing
- ISO 898‑1 – Mechanical properties of fasteners – Part 1: Bolts, screws and studs – for fastener testing
- GB/T 1040 – Plastics – Determination of tensile properties – the Chinese national standard for tensile testing
- GB/T 1449 – Fibre‑reinforced plastic composites – Determination of flexural properties – the Chinese national standard for flexural testing
- GB/T 16823 – Torque‑clamp force testing of fasteners – for torque testing
Report Acceptance and Regulatory Recognition
All tests for GFRP parts and threaded sealants 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 (material, dimensions, fibre content, resin type, sealant type), the test method and conditions (temperature, pressure, test duration), the measured parameters (tensile strength, flexural strength, chemical resistance, sealing performance, adhesion strength, torque retention), a statistical summary (mean, standard deviation, coefficient of variation), 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.
