ASTM D5766 Open Hole Tensile Test | Notched Composite Laminate OHT Tensile Testing Machine

Information on the most widely used ASTM standards within the materials testing industry

Descriptions of the most prominent lSO standards within the materials testing industry

Standards including EN, DIN, JlS, and more

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ASTM D5766 Open Hole Tensile Tester | Composite Laminate OHT Testing | UnitedTest

ASTM D5766 standard tests open-hole tensile strength (OHT) of multidirectional fiber-reinforced polymer composite laminates, simulating structural fastener cut-out notch effects. UnitedTest manufactures ASTM D5766 compliant notched composite tensile testing machines for aerospace structural quality control.

ASTM D5766 is a key standardized test method dedicated to evaluating the open-hole tensile strength (OHT), also known as notched tensile strength, of multi-directional fiber-reinforced polymer matrix composite laminates. Built upon the classic ASTM D3039 tensile testing framework, this method uses standard tensile coupons with a precision-machined central through-hole, loaded under uniaxial tension until structural failure occurs.

This test effectively quantifies the notch sensitivity and stress concentration effect caused by central perforations on composite laminates. It accurately simulates real-world fastener cut-outs, drilling holes and structural cutaway features widely applied in aerospace, automotive and wind energy composite structures. ASTM D5766 test data provides critical performance parameters for structural design safety verification, damage tolerance evaluation, composite material qualification and batch production quality inspection.

UnitedTest designs and manufactures high-precision ASTM D5766 open-hole tensile testing machines fully compliant with standard test specifications. Our professional composite test equipment delivers stable uniaxial tension loading, precise failure data recording and repeatable OHT test results, ideal for advanced composite laboratories, aviation material R&D institutions and industrial structural component certification.

Test Principles:

A balanced, symmetric multi‑directional laminate coupon containing a centrally located circular hole is loaded in uniaxial tension to failure, following the apparatus, alignment and procedure rules of ASTM D3039/D3039M.

The key conceptual point: the hole creates a stress concentration and a reduced net section, and the resulting failure is governed by that notch. Strength is nevertheless reported on the gross cross‑sectional area (w × h), deliberately ignoring the hole . This is an aerospace design convention: it folds the effect of the notch into the strength number itself so the value can be used directly as a notched design allowable (a "remote stress") without re‑computing stress concentrations for fastener holes, free edges, flaws or damage not explicitly modelled in the stress analysis .

The only acceptable failure mode is one that passes through the hole. Anything else is invalid data.

ASTM D5766 open-hole tensile test for composite laminates

Test Specimen information

Laminate	Multi‑directional, balanced and symmetric about the test direction; fibers in ≥2 directions; continuous‑fiber or discontinuous‑fiber (tape and/or fabric)
Standard lay‑up	Typically `[45ᵢ/−45ⱼ/0ⱼ/90ₖ]ms` tape or `[45ᵢ/0ⱼ]ms` fabric, with ≥5 % of fibers in each of the four principal orientations — this family gives the highest likelihood of acceptable failure modes. Not suitable for unidirectional (single‑orientation) tape laminates.
Thickness	Nominal 2.5 mm [0.10 in.], permissible 2–4 mm [0.080–0.160 in.]
Width	36 ± 1 mm [1.50 ± 0.05 in.] (both configurations)
Length	Config. A: 200–300 mm [8–12 in.] (preferred, general lay‑ups); Config. B: 150–200 mm [6–8 in.] (limited to quasi‑isotropic lay‑ups, grip length 35–55 mm, ungripped length ≥75 mm)
Hole	Central, 6.00 ± 0.06 mm [0.250 ± 0.003 in.] diameter; centered along length to within 0.12 mm [0.005 in.] and across width to within 0.05 mm [0.002 in.]
Tabs	Optional; generally not needed — the hole is a sufficient stress riser to force failure in the notched region
Hole preparation	Drill undersized then ream to final size; must not delaminate or otherwise damage material around the hole. Backing the laminate with a sacrificial board and using composite‑specific drills are standard shop practice. Method must be recorded and reported.
Key ratios	w/D = 6 (maintain unless the study is about this ratio); D/h preferred 1.5–3.0

Test Equipment required of ASTM D5766 open-hole tensile test for composite laminates

Universal testing machine	Conforms to ASTM D3039/D3039M requirements, capable of controlled constant cross‑head speed, continuous force‑displacement recording.
Micrometer or gauge	capable of measuring hole diameter to ±0.025 mm [±0.001 in.] — an explicit additional requirement beyond D3039 .
Edge‑mounted extensometer	Installed on specimen edges across the hole gage section, used to capture local strain response and compute percent bending of the coupon.
Specimen machining tools	Undersize drill + reamer for hole fabrication (to avoid hole‑edge delamination damage)
Temperature chamber	for non‑ambient testing (electric heating, CO₂ or LN₂ cooling), plus thermocouples.

Test parameters and stipulations

Speed: in practice ≈2 mm/min crosshead rate (chosen so failure occurs in roughly 1–10 min)

Sampling rate: 2–3 Hz, ≥100 points/test.

Dimensional measurements: Measure actual hole diameter D, specimen width w, thickness h

Step-by-Step Test Procedure of ASTM D5766 open-hole tensile test for composite laminates

Pre‑test preparation: Confirm sampling method, specimen geometry, conditioning scheme, extensometer requirements, and target test parameters. Measure width, thickness, and precisely measure hole diameter; inspect hole edges for delamination damage.
Environmental conditioning (if specified): Condition specimens per D5229/D5229M and keep specimens in conditioning environment until test execution; document moisture content and exposure parameters.
Mount specimen in tensile machine: Align specimen axially; fit edge‑mounted extensometers across the hole gage section if strain measurement is needed.
Conduct tensile test: Run monotonic tensile loading following D3039/D3039M procedure. Continuously record force‑crosshead‑displacement (and force‑strain with extensometer). Capture force at initial damage events, maximum force, rupture‑point displacement.
Post‑test inspection: Record three‑character failure‑mode code for each specimen. Discard results for coupons failing outside the hole gage‑middle zone and perform retest.
Data computation: Calculate open‑hole tensile strength, actual w/D, actual D/h, sample average, standard deviation and CV. Report values to three significant figures where required.

Industry applications

Aerospace & defense (the primary driver): notched design allowables for wing/fuselage skins, covers, frames and control surfaces; bolted‑joint bearing/bypass analysis; material qualification and specifications; quality assurance / batch acceptance .

Automotive & motorsport: carbon‑fiber structures with mechanically fastened joints or cut‑outs.

Wind energy: blade root and structural laminates with holes/cut‑outs.

Marine, rail, infrastructure: composite panels and joints in harsh environments.

R&D and material development: quantifying notch sensitivity, comparing lay‑ups, fiber/matrix systems, drilling processes and toughening strategies; validating progressive‑damage FE models.

Data generated with this method feeds CMH‑17 (Vol. 1 Ch. 2 material characterization; Vol. 3 Ch. 11 bolted joints; Ch. 12 damage‑tolerance allowables) databases .

Related Standard:

ISO 527‑4 / ISO 527‑5	tensile properties of isotropic and orthotropic fiber-reinforced plastic composites. tensile properties of unidirectional fiber-reinforced composites. These are the nearest ISO counterparts; a formal ASTM/ISO harmonization study exists, but specimen dimensions, grip recommendations and the modulus chord differ.
ASTM D3039	Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials
GB/T 3354	Test method for tensile properties of orientation fiber reinforced polymer matrix composite materials
EN 2561 / EN 2597	European aerospace series CFRP unidirectional laminate tensile test parallel (and transverse) to the fiber direction.
SACMA SRM 4R-94	Legacy industry method, historically used alongside early D3039 editions
ASTM D3479	tension–tension fatigue; explicitly uses the D3039 specimen geometry.
ASTM D5766	open-hole (notched) tensile strength.
ASTM D6484	Open‑Hole Compressive Strength
ASTM D6742	Filled‑Hole Tension & Compression Practice
ASTM D7291	through-thickness ("flatwise") tensile strength and modulus.
ASTM D3518	in-plane shear response by tensile test of a ±45° laminate; same straight-sided coupon, no fixture.

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WDW Series Computer Control Electronic Universal Testing Machine made by UNITEDTEST range from 100N to 600KN load capacity with various models like single columns, table type, door frame type etc., is used to perform tension, compression, flexure/bending, shearing, peeling etc., test for metal and nonmetal specimens.

Hydraulic wedge test grips are a robust and versatile solution for tensile testing of high-strength materials. It can be used in both static and dynamic materials testing applications – from 20KN to 500 kN force capacity for dynamic tests, and up to 600 kN for static tests.

Temperature furnace chamber for tensile testing machine, furnace have a columnar split structure, three stage control function. Mainly consists of furnace, temperature controller, high temperature pull rod, high temperature clamp, high temperature extensometer and supporting device.

Video extensometer, is a non-contact real-time high-precision strain measurement system, which is based on a separate camera and real-time image processing algorithm, by taking images of the experimental process, analyzing image characteristic changes, dynamically measuring the strain changes.

Q1: What is ASTM D5766 test used for?

A1: ASTM D5766 measures open‑hole tensile strength (OHT) of balanced‑symmetric multi‑directional polymer‑matrix composite laminates. It evaluates tensile performance weakened by a central drilled hole, simulating fastener holes, cut‑outs or access openings found in real composite structural parts.

Q2: Why is ASTM D5766 test important for composite materials?

A2: Composite laminates are highly notch‑sensitive, without metal‑like plastic yielding to relieve stress concentration around holes. Un‑notched tensile results (ASTM D3039) overestimate real‑world component capacity. D5766 generates reliable notched design allowables for aerospace, automotive composite structural sizing, material qualification and laminate lay‑up optimization. It also reflects hole‑drilling manufacturing quality via test strength variation.

Q3: What are valid failure modes for ASTM D5766 test? When should I discard test data?

A3: Only three valid three‑place failure‑mode codes are allowed: LGM (Lateral‑Gauge‑Middle), AGM (Angled‑Gauge‑Middle), MGM (Multi‑mode‑Gauge‑Middle). Failure must occur in the gauge‑middle zone right at the open hole. If fracture appears in grip region or away from the central hole, the test result is invalid and retest is required, unless studying pre‑existing flaws intentionally.

Q4: What are Configuration A and Configuration B specimens? What is difference?

A4:

Configuration A (preferred general‑purpose): Specimen length 200‑300 mm, for most balanced‑symmetric multi‑directional laminates. Long enough to build uniform strain field outside hole‑influence area.
Configuration B: Specimen length 150‑200 mm, limited only to quasi‑isotropic stacking sequences. Minimum un‑gripped length ≥75 mm to avoid grip‑boundary effect on hole‑zone failure. Both versions share nominal width = 36 mm, hole diameter = 6 mm, nominal w/D ratio = 6.

Q5: Why keep w/D (width‑to‑hole‑diameter) ratio =6 in ASTM D5766?

A5: Stress distribution near the hole interacts with specimen side edges. Fixed w/D=6 minimizes edge‑interference effect and creates comparable stress concentration state, so test data from different laboratories and specimen batches can be directly compared. Both nominal ratio and measured actual ratio must be reported to three significant figures in final report.

Q6: Do I need bonded tabs for ASTM D5766 test coupons?

A6: Tabs are optional and generally not required. The central hole acts as strong stress riser to force failure within hole gauge‑middle area. Tabs can still be applied if you encounter premature grip‑area damage, but it is not mandatory per the standard.

Q7: Can I directly use ASTM D3039 un‑notched tensile strength for composite parts with bolt holes?

A7: No. It is a risky shortcut in composite design. The open hole produces heavy strength reduction by stress concentration. Real composite structures with fastener holes must use open‑hole tensile allowables generated from D5766 rather than un‑notched D3039 values for structural safety design.

Q8. What is the difference between ASTM D5766 and ASTM D3039?

A8: D3039 measures unnotched tensile properties and is the base method D5766 refers to for apparatus, geometry, alignment and procedure. D5766 adds the hole and yields a notched allowable. Unnotched data is for basic material characterisation; OHT data is what structures containing holes are sized on. They are complementary, never interchangeable — OHT is commonly 40–50 % below unnotched strength for quasi‑isotropic CFRP/GFRP.

Q9. How does UnitedTest support ASTM D5766 testing?

A9: UnitedTest supplies electromechanical and hydraulic universal testing machines with the force accuracy (ISO 7500‑1 Class 0.5/1, ASTM E4), stepless speed control and gripping needed for D5766, plus wedge and pneumatic grips, compression platens, extensometers, environmental chambers and fixtures built to ISO, ASTM, EN and DIN requirements. SmartTest software lets you build a D5766 method with gross‑area strength calculation, w/D and D/h ratios, failure‑code entry and automatic mean, standard deviation and CV statistics, then generate a compliant report. Send UnitedTest your material, lay‑up, coupon size and expected failure load, and the team will specify the frame, load cell, grips, extensometer and chamber for your application.

Q10: Why choose ASTM D5766 Open‑Hole Tensile Testing Machine from UnitedTest?

A10: UnitedTest manufactures high‑performance universal testing machines fully compliant with ASTM D5766/D5766M‑23 standard for open‑hole tensile strength test of polymer‑matrix composite laminates. Suitable for CFRP, GFRP tape & fabric composite coupons for aerospace, automotive composite material qualification, R&D and quality control. Complete test fixtures, precision extensometer and dedicated composite test software available.

UnitedTest is a professional manufacturer of material testing equipment supplying complete solutions for ASTM D5766/D5766M‑23 open‑hole tensile strength test for polymer‑matrix composite laminates.

Our universal tensile test system performs standard open‑hole tension test for multi‑directional balanced‑symmetric composite laminates (continuous‑fiber tape, fabric or discontinuous‑fiber reinforced composites). It simulates real‑world stress concentration around fastener holes and cut‑outs, measuring open‑hole tensile strength (OHT) for composite material screening, structural design allowable generation, incoming‑material QC and aerospace‑grade composite qualification.

✅ Full compliance with ASTM D5766‑23 requirements

Compatible with both Configuration A and Configuration B specimen geometries
High‑accuracy load‑cell, stable cross‑head speed control following ASTM D3039 baseline requirements
Supports edge‑mounted extensometer for local strain measurement and percent‑bending calculation
Dedicated composite test software: auto‑calculates OHT strength, w/D ratio, D/h ratio, mean value, standard deviation and CV coefficient of variation; supports recording LGM / AGM / MGM failure‑mode codes; exports complete D5766‑compliant test reports.
Optional customized test fixtures, anti‑slip wedge grips, micrometer accessories for hole‑diameter inspection.

We offer customization to meet your specific needs. Our expert team will collaborate with you to develop the perfect product for you