ISO 14130
Short-Beam Interlaminar Shear Strength of Composites

Universal Grip ISO 14130 short-beam shear (ilss) fixture

Downloads: ISO 14130 Short-Beam Shear (ILSS) Fixture – Universal Grip Data Sheet (PDF)

Written by Chris Thomas, Universal Grip Company · Reviewed by Frank Bertini · Updated October 24, 2026

ISO 14130 is the international standard for the apparent interlaminar shear strength (ILSS) of fibre-reinforced plastic composites by the short-beam method. A short, thick bar, 20 × 10 × 2 mm in the standard size, is bent in three-point loading on a span only five times its thickness, so that the beam fails by shear between the plies rather than by bending of the outer fibres. The single result, the apparent interlaminar shear strength in MPa, is the fastest and cheapest measure of how well a resin bonds to its fibres and how well a laminate is consolidated, which is why it is the universal screening test for prepregs, resin systems, cure cycles and production panels in aerospace, wind energy and automotive composites. It is the ISO counterpart of ASTM D2344 and the aerospace standards EN 2563 and EN 2377.

The test looks trivial and is easy to get wrong: the rollers have specific radii, the span is held to ±0.3 mm, the speed is fixed at 1 mm/min, and only two of the six possible failure modes count as a shear strength. This guide gives the exact specimen and fixture geometry with tolerances, the scaling rule for thicker laminates, the procedure, the formula with worked examples and a capacity calculation, the failure-mode rules, a numeric comparison with ASTM D2344 and EN 2563, and the fixture and machines Universal Grip supplies. The shear testing page gives the lab overview, the composite shear comparison puts short-beam shear beside the V-notch and rail methods, and the ISO standards hub lists every ISO method we equip.

In this guide: What ISO 14130 Measures and Why the Strength Is 'Apparent' · Editions: 1997, Corrigendum 2003 and the ISO 4585 Legacy · Specimen Dimensions and the Scaling Rule · Fixture Geometry: Span 5h, R5 Nose, R2 Supports · Speed, Procedure and Stopping · The Formula, a Worked Example and Capacity · Failure Modes: What Counts as an ILSS · ISO 14130 vs ASTM D2344 vs EN 2563 · Common Errors · Equipment for ISO 14130: Fixture, Inserts, Machines · FAQ

What ISO 14130 Measures and Why the Strength Is 'Apparent'

The standard applies to fibre-reinforced thermoset and thermoplastic composites, in practice continuous-fibre laminates of carbon, glass or aramid, tested as a simply supported beam with a central load. In a beam the shear stress varies parabolically through the thickness and peaks at the neutral plane, where it equals 3F/(4bh). When the span-to-thickness ratio is small, that mid-plane shear stress reaches the interlaminar strength before the outer-fibre bending stress reaches the tensile or compressive strength, and the laminate splits between plies. The stress at that moment is the apparent interlaminar shear strength τM.

The word 'apparent' is deliberate. Beam theory assumes a pure parabolic shear distribution, but under the loading nose the real stress state is a mix of shear and through-thickness compression, the span is so short that the plies carry load partly as a compression strut, and the nose indents the surface. The number is therefore reproducible and useful for ranking materials, batches and cure states, but the standard says it is not suitable for design parameters, and clause 1 restricts it to cases where interlaminar shear failure is actually obtained. Design-level shear properties come from ASTM D5379 V-notch or ISO 14129 ±45° tension; a quick comparison of the methods is on our composite shear fixtures post.

Apparent interlaminar shear stress τ: the shear stress on the neutral plane calculated from F, b and h.
Apparent interlaminar shear strength τM: τ at failure or at the maximum force, whichever occurs.
Direction 1 and 2: parallel and transverse to the fibres; specimens A and B are cut in each when the laminate has no dominant orientation.

Editions: 1997, Corrigendum 2003 and the ISO 4585 Legacy

ISO 14130 was published in December 1997 and replaced ISO 4585:1989, the earlier short-beam standard. Technical Corrigendum 1 of November 2003 is editorial. There is no amendment and no second edition; BS EN ISO 14130:1998, EN ISO 14130:1997 and DIN EN ISO 14130:1998 are the same text with national covers. The 1997 foreword carried over an alternative specimen from ISO 4585, 30 × 15 × 3 mm on a 15 mm span, and notes that the width changed from 10 to 15 mm for that size; it is easy to misread the foreword and take 15 mm as the standard span. The standard specimen is 20 × 10 × 2 mm on a 10 mm span. The standard has no precision statement, so it warns that the method may not be suitable for specifications or disputes until interlaboratory data exist.

Specimen Dimensions and the Scaling Rule

The standard specimen (clause 6.1) is a flat rectangular bar with thickness h = 2 ± 0.2 mm, length l = 20 ± 1 mm and width b = 10 ± 0.2 mm. The general rule in 6.1.2 is length = 10h and width = 5h, so thicker laminates scale up: 3 mm → 30 × 15 × 3 mm on a 15 mm span; 4 mm → 40 × 20 × 4 mm on a 20 mm span. The note under 6.1 is important: 2 mm specimens of some materials fail by compression under the nose or by excessive deflection rather than by shear, and in that case a thickness that does produce horizontal shear failure should be chosen. Carbon/epoxy at 2 mm almost always shears cleanly; a tough thermoplastic laminate or a soft glass/polyester often needs 3 or 4 mm.

Preparation: machined from moulded blanks or sheet per ISO 1268, machining per ISO 2818; flat, free of twist, edges square and undamaged; the moulded (unmachined) face goes against the supports.
Uniformity: thickness within ±5 % of the mean along the specimen, width constant within 0.2 mm.
Measurement: width to 0.02 mm and thickness to 0.05 mm at mid-length, with a flat-anvil micrometer (hemispherical for textured surfaces).
Number: at least five specimens; if the laminate has no dominant fibre direction, five in each principal direction (A and B), otherwise in the preferred direction.
Conditioning: per the material specification, otherwise ISO 291; test in the same atmosphere unless elevated or reduced temperature is agreed.

Width matters more than it looks. The standard accepts 2h as the minimum in the scaling rule only through the preferred 5h; a narrow coupon has a larger fraction of edge-cut fibres and free-edge stresses and gives a lower, more scattered strength. Cutting 20 mm coupons from a panel is best done with a diamond saw and a jig that holds several strips at once, then deburring the edges without rounding them.

Fixture Geometry: Span 5h, R5 Nose, R2 Supports

ISO 14130 specifies the contact geometry in clause 5: the loading member has a radius r1 = 5 ± 0.2 mm (a 10 mm diameter cylinder) and the two supports have a radius r2 = 2 ± 0.2 mm (4 mm diameter). Nose and supports must be longer than the specimen is wide and parallel to one another, and the span must be adjustable. The span L is set to five times the mean thickness of the specimen set, L = 5h ± 0.3 mm, which is 10.0 mm for the standard specimen; a shorter span is permitted for materials that will not fail in shear at 5:1. The specimen is centred on the supports with the unmachined face down. No hardness is specified for the contact surfaces, which is one of the differences from ASTM D2344's 60 to 62 HRC, but hardened, ground rollers are what keep the radii true after a few hundred tests.

Setting a 10 mm span to ±0.3 mm by eye is not realistic; the support blocks need to move on a scaled slide or against a spacing gauge, and the span is measured between the roller axes, not the roller edges. The same error that is tolerable on an 80 mm flexure span is 25 % of a short-beam span. The force transducer must meet ISO 5893 class 1 (±1 % of full scale), and because the whole test lasts well under a minute at 1 mm/min with a peak of a few kilonewtons, a load cell sized close to the expected force and a data rate of at least 10 Hz are needed to catch the first load drop.

Speed, Procedure and Stopping

The crosshead speed is 1 mm/min ± 0.2 mm/min unless the material standard says otherwise. Force is recorded continuously against crosshead displacement; no extensometer or deflectometer is used, because no modulus is calculated. The standard does not define a stop criterion beyond 'failure or maximum force', so laboratories generally stop at a 30 % drop from the peak, when the specimen separates, or when nose travel exceeds the thickness, which is the ASTM D2344 rule and a sensible one. The procedure:

Measure b and h at mid-length; compute the mean thickness of the set and set the span to 5h ± 0.3 mm.
Fit the R5 nose and R2 supports and check that they are parallel and longer than the specimen width.
Place the specimen centrally, unmachined face on the supports, fibres (direction 1) along the span.
Apply a small contact preload, zero the force, and run at 1 mm/min.
Record the force-displacement trace to the stop point; note the maximum force.
Examine the specimen edge under low magnification and classify the failure mode (next section).
Calculate τ for each valid specimen, then the mean (and standard deviation per ISO 2602) to three significant figures.
Report per Clause 11: 'ISO 14130/1' (the /1 is the speed), material and layup, machine class, loading and support radii, specimen preparation and direction, dimensions, number tested, individual and mean results, failure modes, conditioning and date.

The Formula, a Worked Example and Capacity

With F the force in newtons, b the width and h the thickness in millimetres, the apparent interlaminar shear stress is τ = 3F / (4bh) in MPa, and τM uses the force at failure or the maximum force. There is no span term: the shear stress on the neutral plane of a centrally loaded beam does not depend on the span, which is why the short span is a means of forcing shear failure, not part of the calculation.

Worked example, carbon/epoxy unidirectional. Specimen 20.0 × 10.0 × 2.00 mm, span 10.0 mm, 1 mm/min. The trace rises linearly to 2,900 N and drops sharply with a single horizontal crack at mid-thickness. τM = 3 × 2,900 / (4 × 10.0 × 2.00) = 8,700 / 80 = 109 MPa, a typical value for aerospace carbon/epoxy (published round-robin values are about 108 ± 6 MPa). A glass/epoxy laminate of the same size failing at 1,200 N gives 3,600 / 80 = 45 MPa, in the normal 40 to 70 MPa band for glass systems. A 3 mm alternative specimen, 30 × 15 × 3 mm, at 100 MPa carries F = 4bhτ/3 = 4 × 15 × 3 × 100 / 3 = 6,000 N.

Capacity. The force needed is F = 4bhτ/3. For the standard 10 × 2 mm section at a high carbon ILSS of 120 MPa that is 4 × 10 × 2 × 120 / 3 = 3,200 N; at 4 mm thickness and 20 mm width it rises to 12.8 kN. A 10 kN fixture with a 5 or 10 kN load cell therefore covers every 2 and 3 mm specimen, and a 25 kN frame covers scaled 4 mm coupons. Because the loads are modest and the stroke is tiny, the fixture's stiffness and the squareness of the nose to the supports matter more than the frame's capacity.

Failure Modes: What Counts as an ILSS

Clause 9.7 and Figure 4 classify six failure modes and accept only two of them. Single shear is one horizontal crack at or near mid-thickness running from under the nose towards a support; multiple shear is several such cracks at different plies. Both are valid, and the result is an interlaminar shear strength. The other four are not: mixed failure (shear combined with tension or compression), tensile failure of the bottom face, compressive failure or crushing under the nose, and plastic shear, where the beam yields and bends without a clear crack. If any of these occur the standard says the value is not an interlaminar shear strength and may only be used to compare specimens of the same material.

Tension failure on the bottom face: the span is too long for the material or the laminate has a high ILSS relative to its flexural strength; shorten the span (a smaller ratio is permitted) or use a thicker specimen.
Crushing under the nose: soft or low-modulus matrix, a damaged or undersized roller, or a thin specimen; move to 3 or 4 mm, check the R5 nose, consider a thin cushion only if the material specification allows it.
Plastic shear: tough thermoplastic matrices (PEEK, PA) and some vinyl esters deform instead of cracking; the short-beam test is simply not discriminating for them and a V-notch test is the alternative.
Mixed: usually a span slightly too long for a glass laminate; the first drop may still be a shear event, but the standard requires a clean classification.

Record the mode for every specimen, because a set with three valid shears and two crushes is reported as three results, not five, and a laboratory that quietly averages all five is reporting a number the standard does not recognise. Inspection is quick with a 10× loupe on the polished edge; a dab of white marker on the edge before the test makes the crack obvious afterwards.

ISO 14130 vs ASTM D2344 vs EN 2563

The three short-beam standards use the same 0.75 F/(bh) arithmetic and give results that track each other, but the geometry differs enough that the numbers are not interchangeable and the fixtures need different inserts:

ISO 14130: standard specimen 20 × 10 × 2 mm (l = 10h, b = 5h); span 5h ± 0.3 mm = 10 mm; loading nose R5 ± 0.2 (Ø10), supports R2 ± 0.2 (Ø4); no hardness requirement; 1 ± 0.2 mm/min; flat specimens only; ≥5 specimens; failure or maximum force, no stop criterion stated.
ASTM D2344/D2344M: span-to-thickness 4.0; specimen length 6h, width 2h, thickness 2 to 6 mm (for 2 mm: 12 × 4 × 2 mm on an 8 mm span); nose R3.00 (Ø6.00 mm) and supports R1.50 (Ø3.00 mm) in D2344M, 0.250 and 0.125 in in D2344; 60 to 62 HRC; 1.0 mm/min; stop at a 30 % force drop, two-piece failure or nose travel greater than the thickness; flat and curved specimens; ≥5.
EN 2563 (carbon, aerospace) and EN 2377 (glass): 5:1 span like ISO, with tight ±0.02 mm centring and parallelism tolerances on the anvils and 6 mm diameter noses and supports in the common fixture kits.

The practical consequences: an ISO coupon is 2.5 times wider than an ASTM coupon of the same thickness and sees fewer edge effects; the ISO 5:1 span puts slightly more bending into the beam than the ASTM 4:1, so soft matrices are more likely to fail in tension or mixed mode under ISO; and the ASTM R3/R1.5 rollers are sharper than the ISO R5/R2, which raises the contact stress and tends to lower the result by a few percent. A laboratory serving both markets keeps both roller sets and reports which standard, span and radii were used. Our ASTM D2344 guide gives the ASTM side in the same detail and uses the same ISO figures as this page: 20 × 10 × 2 mm, 10 mm span, Ø10 nose, Ø4 supports, 1 mm/min.

Common Errors

Span measured to the roller edges: on a 10 mm span, measuring between the inside edges of Ø4 supports gives a true span of 14 mm, a 7:1 ratio and a beam that fails in bending.
D2344 rollers on an ISO test: R3/R1.5 inserts are not the ISO R5/R2 geometry; the report must state the radii, and the result is not comparable to ISO data.
Taking the foreword's 15 mm span as standard: that belongs to the 3 mm alternative specimen; the 2 mm specimen runs on 10 mm.
Machined face on the supports: the standard puts the unmachined face down; cutting marks on the tension face start cracks early.
Averaging invalid failures: crushed or plastically sheared specimens are not an ILSS and are reported separately.
Thickness mis-measurement: h is in the denominator and also sets the span; a 0.1 mm error on a 2 mm laminate is 5 % on the result and 0.5 mm on the span setting.
Treating the value as a design allowable: it is a screening number; use V-notch or ±45° tension for design.
Too few samples per direction: fabrics and multiaxials with no dominant direction need five in each of directions A and B.

Equipment for ISO 14130: Fixture, Inserts, Machines

The Universal Grip ISO 14130 short-beam shear fixture is a three-point bend fixture built for short spans: the support blocks slide in a scaled T-slot beam for quick, accurate setting of the 5h span, and a radiused loading nose on the upper beam loads the specimen centrally so that failure occurs by interlaminar shear. The loading nose and supports are interchangeable, radiused per ISO 14130 geometry (R5 nose, R2 supports), with hardened, ground contact surfaces, and the same inserts also suit flexure and plate-twist tests, which is why the fixture photographed is a multi-standard kit shared with the ISO 15310 plate-twist method and with the long-span ISO 14125 flexure specimens. It is rated 10 kN standard with higher capacities on request, built with stainless steel beams and hardened inserts, and supplied with clevis-pin or threaded adapters to suit your frame. When ordering, specify the specimen thickness and span, the loading nose and support radii, the capacity and the machine connection; R3/R1.5 inserts are available for ASTM D2344M on the same base.

Machines. With peak forces of 1 to 4 kN on standard coupons, a 5 kN benchtop UTM is the natural home for an ILSS fixture, and a 10 kN frame adds headroom for 3 and 4 mm coupons and shares the fixture with ISO 14125 and ISO 178 flexure. Choose a load cell no larger than about five times the expected peak so the 1 % class requirement is met at the failure force, and set the data rate to 10 Hz or faster. Hot/wet ILSS testing, a routine qualification step for aerospace prepregs, puts the fixture inside an environmental chamber.

Choosing between the shear methods. Short-beam shear is the fastest way to rank resins, cure cycles and consolidation quality and needs no strain measurement. When you need a shear modulus, a design value or the in-plane shear response, the V-notch (ASTM D5379) and rail-shear fixtures on our shear fixtures page and the composite fixture buyer's guide cover the alternatives. Tensile and compressive properties of the same laminates are covered by ISO 527-4, ISO 527-5 and ISO 14126.

ISO 14130 FAQ

What is ISO 14130?

ISO 14130 is the international standard for the apparent interlaminar shear strength (ILSS) of fibre-reinforced plastic composites by the short-beam method: a 20 × 10 × 2 mm bar is loaded in three-point bending on a 10 mm span (5 × thickness) at 1 mm/min until it fails by shear between plies. The edition is ISO 14130:1997 with Corrigendum 1:2003; it replaced ISO 4585.

What are the ISO 14130 specimen dimensions?

Thickness 2 ± 0.2 mm, length 20 ± 1 mm, width 10 ± 0.2 mm. The general rule is length = 10h and width = 5h, so a 3 mm laminate is tested as 30 × 15 × 3 mm on a 15 mm span and a 4 mm laminate as 40 × 20 × 4 mm on a 20 mm span. Thickness must be within ±5 % of the mean along the specimen and width constant within 0.2 mm.

What span and roller radii does ISO 14130 use?

Span L = 5h ± 0.3 mm, i.e. 10 mm for the standard 2 mm specimen, measured between roller axes. The loading nose radius is 5 ± 0.2 mm (10 mm diameter) and the support radius 2 ± 0.2 mm (4 mm diameter). No hardness is specified, unlike ASTM D2344's 60–62 HRC.

What is the test speed in ISO 14130?

1 mm/min ± 0.2 mm/min unless the material specification states otherwise. Force is recorded continuously; no extensometer is needed because the method reports strength only, not a modulus.

How is interlaminar shear strength calculated in ISO 14130?

τ = 3F/(4bh), with F in newtons and b, h in millimetres, giving MPa; τM uses the force at failure or the maximum force. Example: 2,900 N on a 10.0 × 2.00 mm section gives 3 × 2,900 / 80 = 109 MPa. The span does not appear in the formula.

Which failure modes are valid in ISO 14130?

Single shear (one horizontal crack near mid-thickness) and multiple shear (several interlaminar cracks) are valid. Mixed shear-plus-tension or shear-plus-compression, tensile failure, compressive crushing under the nose and plastic shear are not; those results are not an interlaminar shear strength and may only be used to compare specimens of the same material.

How many specimens does ISO 14130 require?

At least five. If the laminate has no dominant fibre direction, five in each of the two principal directions (specimens A and B). Results are reported individually and as a mean to three significant figures, with the standard deviation optional.

What is the difference between ISO 14130 and ASTM D2344?

ISO 14130: 5:1 span, fixed 20 × 10 × 2 mm specimen (10h × 5h), R5 nose / R2 supports, no hardness spec, flat specimens only. ASTM D2344: 4:1 span, specimen 6h long × 2h wide (12 × 4 × 2 mm at 2 mm), R3 nose / R1.5 supports at 60–62 HRC, 30 % load-drop stop, flat and curved specimens. Both use 0.75 F/(bh) and 1 mm/min, but results are not interchangeable.

Why is the ISO 14130 result called 'apparent' shear strength?

Because the beam-theory parabolic shear distribution is only approximate at a 5:1 span: through-thickness compression and indentation under the nose and the strut action of the short beam change the real stress state. The number is reproducible for ranking materials and checking consolidation but, as the standard says, is not suitable for design parameters.

What typical ISO 14130 values should I expect?

Aerospace carbon/epoxy unidirectional laminates give roughly 100–120 MPa (round-robin data around 108 MPa); glass/epoxy 40–70 MPa; glass/polyester and vinyl ester often 25–45 MPa. Values well below these on a known material point to poor consolidation, voids or incomplete cure.

What machine capacity is needed for ISO 14130?

Small: F = 4bhτ/3, so a 10 × 2 mm carbon coupon at 120 MPa needs 3.2 kN and a 20 × 4 mm coupon at 120 MPa about 12.8 kN. A 5 or 10 kN benchtop UTM with a 10 kN fixture covers the standard and 3 mm specimens; use a load cell no more than about five times the expected peak.

Can ISO 14130 be run on the same fixture as ISO 14125 flexure?

Yes. Universal Grip's short-beam fixture uses interchangeable radiused inserts on a scaled T-slot beam, so the R5/R2 ISO 14130 set, the R5/R2 and R5/R5 ISO 14125 sets and R3/R1.5 ASTM D2344M inserts fit the same base; only the span setting and inserts change between a 10 mm ILSS test and an 80 mm Class IV flexure test.

Need a short-beam shear fixture with ISO 14130 rollers, or a complete ILSS system? Contact Universal Grip with your laminate thickness, expected shear strength and machine connection and we will quote the right setup.

Literature

Pricing and Availability

ISO 14130 Short-Beam Interlaminar Shear Strength of Composites