ASTM D1002 - Lap Shear Tensile Test

Downloads: Standard Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading (Metal-to-Metal) - PDF

Written by Chris Thomas, Universal Grip Company · Reviewed by Frank Bertini · Updated October 31, 2026

ASTM D1002 is the standard test method for the apparent shear strength of adhesives that bond metal to metal, measured on a single-lap-joint specimen pulled in tension. It is the most widely run adhesive test in the world: aerospace, automotive, electronics and industrial labs use it to compare adhesives, surface treatments, cure cycles and environmental exposure. This guide covers the specimen, the loading rate, how the specimen is gripped, how to calculate and report results, the failure modes you will see, and the equipment Universal Grip builds for the test. It is written from the fixture maker's side of the bench, so it also covers the alignment and gripping details that decide whether a test is valid.

Two things to keep in mind before you start. First, D1002 is a comparative test: the standard itself says the values are not design allowables, because the stress in a single-lap joint is far from uniform. Second, the adhesive manufacturer, not the standard, supplies most of the process details (surface preparation, cure, conditioning), so record them with every data set.

In this guide: What ASTM D1002 Measures · Specimen Dimensions and Panel Layout · Surface Preparation, Bonding and Cure · Test Setup: Grips, Grip Separation and Shims · Test Procedure Step by Step · Calculations and a Worked Example · Failure Modes and What They Tell You · Common Errors and How to Avoid Them · Reporting Checklist · Equipment for ASTM D1002 · Related Standards · FAQ

What ASTM D1002 Measures

The test reports apparent shear strength: the load at failure divided by the bonded area of the overlap. It is called apparent because the stress is not pure shear. The two adherends are offset by their own thickness, so the load path bends them slightly as the joint is pulled, and the adhesive sees a mix of shear and peel that peaks at the two ends of the overlap. The number you get depends on the adhesive, the adherend stiffness, the overlap length and the bondline thickness, which is why the standard fixes all of them.

D1002 is used to answer practical questions rather than to produce design data: which of two adhesives is stronger on aluminum, whether a new surface treatment improves adhesion, how much strength is lost after humidity or salt-spray exposure, and whether a production batch matches the qualification lot. For design values, the adhesive industry uses thick-adherend tests such as ASTM D5656 or finite-element analysis fed by D1002-style data.

Related methods use the same joint for other adherends: ASTM D3163 for rigid plastics, ASTM D5868 for fiber-reinforced plastics, ASTM D3164 for plastic adherends in a laminated assembly, and ASTM D3165 for laminated assemblies with notched adherends. See our ASTM D5868 lap shear page for the FRP version and our lap shear vs. block shear guide for how D1002 compares with ASTM D905 and D4501 block shear.

Specimen Dimensions and Panel Layout

The standard specimen is two metal strips bonded with a short overlap. The figures below are the values in D1002 Figure 1; the tolerances matter because a small change in overlap or thickness changes the result.

• Width: 25.4 mm (1.0 in), measured to 0.25 mm.

• Adherend length: 101.6 mm (4 in) each.

• Adherend thickness: 1.62 ± 0.125 mm (0.064 ± 0.005 in). This is the standard thickness for most metals; thicker adherends are allowed when the adhesive is strong enough to yield the metal at the standard thickness.

• Overlap: 12.7 ± 0.25 mm (0.5 ± 0.01 in), measured to 0.25 mm.

• Bonded area: 25.4 × 12.7 = 322.6 mm² (0.5 in²).

• Adhesive run-out: the adhesive may extend about 6 mm (¼ in) beyond the overlap on the unbonded side; squeeze-out beyond that is trimmed.

• Edges: machined edges should have a surface roughness no coarser than about 160 µin rms so that a rough edge does not start the failure.

Specimens are normally made as a bonded panel and cut into strips afterwards, which keeps the overlap and bondline consistent across a set. The usual panel is two 101.6 mm × 177.8 mm (4 × 7 in) sheets bonded along one 12.7 mm edge; the panel is then sawn into five or more 25.4 mm strips, discarding the outer edges, where the bondline is least uniform. Cut without overheating or bending the joint; a slow bandsaw or waterjet is better than an abrasive cut-off wheel. The standard asks for panels in multiples of five specimens so that each condition is represented by at least five results.

Adherends. The standard names common metals and their material specifications: aluminum alloy 2024-T3 clad (ASTM B209) is the usual choice for qualification work, with brass (B36), copper (B152), carbon steel (A109), 302 stainless (A167) and titanium (B265) also listed. Use the same alloy, temper and thickness across every set you intend to compare.

Overlap limit. The overlap must not be so long that the metal yields before the adhesive fails. The tensile stress in the adherend is the adhesive shear stress multiplied by overlap and divided by thickness, so the maximum overlap is roughly the adherend yield strength times its thickness divided by the expected adhesive shear strength, with a 1.5 safety factor applied to the adhesive strength. For 1.62 mm 2024-T3 (yield about 345 MPa) and a strong structural epoxy at 30 MPa, that limit is about 345 × 1.62 ÷ 45 ≈ 12 mm, which is why the standard overlap is 12.7 mm and why very strong adhesives are sometimes tested on thicker adherends. If an adherend shows a permanent bend or necking after the test, the result is not a valid shear strength.

Surface Preparation, Bonding and Cure

D1002 leaves surface preparation, adhesive application and cure to the adhesive manufacturer's instructions, and it requires you to report them. Follow the instructions exactly and record them, because surface preparation is usually the single biggest influence on the result.

• Cleaning and treatment: solvent wipe, abrasion, alkaline clean, etch or anodize per the adhesive data sheet. ASTM D2651 describes standard metal preparation practices, and ASTM D2093 covers plastics.

• Bondline thickness: control it with shims, wire spacers or glass beads, and measure it after cure (adherend stack minus the two metal thicknesses). The report asks for average bondline thickness to the nearest 0.025 mm.

• Assembly: note open time, closed assembly time, temperature and humidity.

• Cure: pressure, time, temperature, heat-up rate and whether temperature was measured at the bondline or in the oven.

• Conditioning before test: the adhesive maker specifies this. Most labs use the ASTM D618 standard atmosphere of 23 ± 2 °C and 50 ± 10 % relative humidity for at least 40 hours, and report any environmental exposure (humidity, salt spray, fluid immersion, heat aging) separately.

Test Setup: Grips, Grip Separation and Shims

A single-lap specimen is offset: the two adherends are not in the same plane. If you clamp the ends in ordinary flat jaws, the load line passes through the center of the jaws but not through the bond, and the specimen is bent as soon as the load comes on. The standard addresses this with three rules.

• Jaws engage the outer 25 mm (1 in) of each adherend. This fixes the free length and the bending stiffness of the joint.

• The distance from the end of the overlap to the jaws is 63 mm (2.5 in) on both sides, and it stays the same even when a non-standard overlap is used.

• Grips must be self-aligning so the load passes through the bond as the specimen straightens.

Shims (spacers). The simplest way to put the load line through the bond plane is to add a shim equal to the adherend thickness behind one end of the specimen in each grip, so the free adherend and the shim together are centered in the jaws. For the standard 1.62 mm adherend, use a 1.62 mm shim, or a short offcut of the same sheet. Grips with built-in offset jaws do the same job without loose shims and are worth it for high-volume labs. Our ASTM D1002 lap shear grips ship with matched spacers for 1.62 mm and 3.2 mm adherends, and we make offset jaw sets to order.

Grip type and jaw faces. Wedge grips are the usual choice for D1002: they tighten as the load rises, so a 25 mm wide aluminum strip does not slip at 5–10 kN. Use serrated faces for steel and titanium and fine-serrated or smooth faces for aluminum and copper, which are soft enough to be marked by coarse teeth. Slippage shows up as a sawtooth or a flat step in the load-extension curve, and jaw marks that run into the overlap mean the specimen was gripped too close to the bond. Pneumatic grips are a good option for high-throughput labs because the clamping force is the same on every specimen. Vise grips work at the 1–5 kN level with the right faces, but need a self-aligning coupling above and below.

Alignment check. Before the first test, load a bare strip of the adherend metal in the grips and watch for bending; a strain-gaged or dial-indicator check between the jaws should show no measurable bow. A joint that fails from one edge of the overlap every time, with a torn or peeled look at that edge, is a sign of misalignment rather than a weak adhesive.

Capacity. The breaking load should fall between 15 % and 85 % of the load cell's range. A structural epoxy at 20–35 MPa on the standard 322.6 mm² area breaks at 6.5–11.3 kN, so a 10 kN or 20 kN load cell is the right size; a 100 kN cell would put the result below 15 % of range. See our universal testing machines for frames from 5 kN to 600 kN, or our motorized tensile testers for low-strength adhesives under 6.7 kN.

Test Procedure Step by Step

• Measure and record the width and overlap of each specimen to 0.25 mm, and the adherend thicknesses. Calculate the bonded area.

• Set the grip separation so each jaw engages the outer 25 mm of the adherend and the lap ends are 63 mm from each jaw.

• Insert the shims or use offset jaws so the bond plane is on the machine's load axis. Close the lower grip first, let the specimen hang straight, then close the upper grip.

• Zero the load. The standard calls for a loading rate of 8.3 to 9.7 MPa per minute (1,200 to 1,400 psi/min) of shear area. In crosshead control this works out to about 1.3 mm/min (0.05 in/min) for a standard joint; in load control, set 2.7 to 3.1 kN/min for the 322.6 mm² area.

• Load to failure and record the maximum load. Most joints fail in 1 to 3 minutes at this rate.

• Examine both bonded faces and estimate the percentage of each failure mode (see below).

• Test at least five specimens per adhesive and condition. Report each result and the average, maximum and minimum.

Loading rate matters. Adhesives are viscoelastic, so a faster pull gives a higher apparent strength. If you compare data sets, make sure they were run at the same rate and in the same control mode; converting between stress rate and crosshead rate depends on the stiffness of the whole load train, so the 1.3 mm/min figure is a starting point, not a substitute for the specified stress rate.

Calculations and a Worked Example

Apparent shear strength = failing load ÷ bonded area. Area is width × overlap. The standard reports the area to the nearest 0.06 cm² (0.01 in²) and strength in MPa or psi.

Example: a 2024-T3 specimen measures 25.4 mm wide with a 12.7 mm overlap, so the area is 322.6 mm². It fails at 6,480 N. Apparent shear strength = 6,480 ÷ 322.6 = 20.1 MPa, or 2,910 psi. If the width measured 25.2 mm and the overlap 12.9 mm, the area is 325.1 mm² and the strength 19.9 MPa; the 1 % difference is why both dimensions are measured on every specimen rather than assumed.

Sizing the machine from the expected strength works the other way: 35 MPa × 322.6 mm² = 11.3 kN, so a 20 kN machine and grips keep the break near 55 % of capacity. For a weak contact adhesive at 2 MPa, the break is only 645 N, and a 5 kN or smaller load cell is needed to stay above 15 % of range.

Load rate conversion: 9.7 MPa/min on 322.6 mm² is 3.1 kN/min. If your machine only runs in crosshead control, run one specimen in load control, note the crosshead speed that gives the correct stress rate, and use that speed for the set.

Failure Modes and What They Tell You

After the break, look at both faces of the overlap and estimate the percentage of each failure type. The standard asks for the estimate in the report, and it is often more useful than the strength value itself.

• Cohesive failure (within the adhesive): adhesive remains on both adherends. This is the result you want; it means the bond was stronger than the adhesive itself and the strength value reflects the adhesive.

• Adhesive (interfacial) failure: the adhesive separates cleanly from one adherend. This points to surface preparation, contamination or a primer problem rather than to the adhesive's strength.

• Substrate (adherend) failure: the metal yields, necks or tears before the bond fails. The joint was stronger than the metal; use thicker adherends or a shorter overlap, and do not report the value as a shear strength.

• Mixed mode: a percentage of each. Report the estimated split, for example 70 % cohesive / 30 % adhesive.

Failure that starts at one end of the overlap and tears across at an angle usually means the specimen was bent during the test, either from missing shims or from grips that were not self-aligning. A failure that always starts at the same edge of the strip points to a bondline that is thicker on one side.

Common Errors and How to Avoid Them

• No shims or offset jaws: the single most common cause of low, scattered results. Peel stress at the overlap ends drops the apparent strength by 10–30 %.

• Gripping too close to the overlap: the standard's 63 mm rule is there to keep jaw pressure and bending away from the bond.

• Wrong loading rate: a 10× faster pull can raise the apparent strength of a toughened epoxy by 10 % or more.

• Uncontrolled bondline thickness: thick bondlines usually test lower. Use spacers and measure after cure.

• Comparing different overlaps or thicknesses: the standard warns that results are only comparable when the joint geometry is identical.

• Overheating during cutting: a hot saw cut can post-cure or soften the adhesive at the edge of the strip.

• Slipping in the grips: fix the jaw face before you question the adhesive. A sawtooth curve is a grip problem.

• Too few specimens: five is the minimum; adhesive data scatter is high enough that three results cannot distinguish two products.

Reporting Checklist

D1002 lists what a complete report contains. Use it as a checklist so data sets can be compared later.

• Adhesive identification, lot and supplier.

• Adherend metal, alloy, temper, thickness and surface preparation.

• Application method, bondline thickness control, assembly conditions and cure cycle.

• Average bondline thickness (to 0.025 mm) and how it was measured.

• Overlap length and specimen width.

• Conditioning and any environmental exposure.

• Number of specimens and number of panels they came from.

• Loading rate and control mode.

• Maximum, minimum and average failing load and apparent shear strength.

• Average estimated percentage of cohesive, adhesive and substrate failure.

The standard includes no precision and bias statement, so keep your own records of repeatability by running a reference adhesive with each batch.

Equipment for ASTM D1002

A complete D1002 setup is a tensile machine, a load cell sized for the adhesive, self-aligning grips with offset jaws or shims, and software that can run in stress-rate control. Universal Grip supplies all of it and fits our grips to Instron, MTS, Shimadzu, ZwickRoell, Tinius Olsen and Mark-10 frames with the right adapters.

• ASTM D1002 lap shear grips: wedge-action grips with matched 1.62 mm spacers and a self-aligning clevis coupling; 10 kN and 20 kN standard, higher on request.

• Wedge grips and pneumatic grips with serrated, fine-serrated or smooth faces for aluminum, steel and titanium adherends.

• Universal testing machines from 5 kN benchtop to floor-standing frames, with stress-rate control.

• Motorized tensile testers for low-strength adhesives and sealants.

• Environmental chambers for hot/wet and sub-zero testing of bonded joints.

Watch the fixture in use in our ASTM D1002 lap shear video on this page, and see the Tensile Grip & Fixture Selection Guide for matching grips to your machine.

Related Standards

• ASTM D3163: lap shear of adhesively bonded rigid plastics, at a slower 1.3 mm/min rate.

• ASTM D5868: lap shear of fiber-reinforced plastic bonded to itself or to metal, at 13 mm/min. See our ASTM D5868 page.

• ASTM D3165: laminated assemblies with notched adherends, which keeps the load line in the bond plane.

• ASTM D5656: thick-adherend lap shear with a KGR extensometer, used to measure adhesive shear stress-strain for design.

• ASTM D905 and D4501: block shear of wood and rigid materials. See our ASTM D905 and ASTM D4501 pages.

• ASTM D1876 and D903: T-peel and 180° peel, which measure peel rather than shear. See ASTM D1876 and ASTM D903.

• ISO 4587 and EN 1465: the international and European equivalents for rigid-to-rigid lap shear; specimen geometry differs slightly (ISO 4587 uses a 12.5 mm overlap on 25 mm wide, 1.6 mm adherends).

For the full list of adhesive tests we build fixtures for, see the adhesive testing guide and shear fixtures.

ASTM D1002 FAQ

What does ASTM D1002 measure?

It measures the apparent shear strength of an adhesive bonding two metal strips in a single-lap joint: the failing load divided by the bonded overlap area, reported in MPa or psi, along with the type of failure.

What are the ASTM D1002 specimen dimensions?

Two metal adherends 25.4 mm (1 in) wide, 101.6 mm (4 in) long and 1.62 mm (0.064 in) thick, bonded with a 12.7 mm (0.5 in) overlap, giving a bonded area of 322.6 mm² (0.5 in²).

What is the ASTM D1002 test speed?

The standard specifies a loading rate of 8.3 to 9.7 MPa per minute (1,200 to 1,400 psi/min) of shear area. In crosshead control this is about 1.3 mm/min (0.05 in/min) for a standard joint.

How far apart should the grips be?

Each jaw engages the outer 25 mm (1 in) of its adherend, and the distance from the end of the overlap to the jaw is 63 mm (2.5 in) on both sides.

Why do I need shims or offset grips?

The two adherends are offset by one thickness, so flat jaws put the load line beside the bond and bend the specimen. A shim equal to the adherend thickness, or offset jaw faces, puts the load through the bond plane.

How many specimens does D1002 require?

At least five per adhesive and condition. Panels are bonded and cut so each condition is represented by multiples of five specimens.

What is a typical lap shear strength?

Structural epoxies on properly prepared aluminum commonly give 20 to 35 MPa (2,900 to 5,000 psi). Acrylics and urethanes are often 10 to 25 MPa, and contact or pressure-sensitive adhesives are usually under 2 MPa. Values depend on surface preparation, bondline thickness and rate.

Is ASTM D1002 strength a design value?

No. The standard states the results are comparative. The stress in a single-lap joint is not uniform, so the number is used to compare adhesives, surface treatments and exposures, not to size real joints.

What is the difference between ASTM D1002 and D3163 or D5868?

They use the same single-lap geometry on different adherends: D1002 is metal to metal, D3163 is rigid plastics, and D5868 is fiber-reinforced plastic bonded to itself or to metal. The test rates also differ.

What load cell capacity do I need?

The breaking load should fall between 15 % and 85 % of the load cell range. A 10 kN or 20 kN cell suits most structural adhesives on the standard specimen; weak adhesives need 1 to 5 kN.

What does cohesive versus adhesive failure mean?

Cohesive failure leaves adhesive on both faces and shows the adhesive itself broke, which is the desired result. Adhesive failure is a clean separation from one surface and points to a surface preparation or contamination problem.

Can I run D1002 on a Mark-10 or small tensile tester?

Yes for adhesives that break below the tester's capacity. A 1,500 lbf (6.7 kN) frame covers adhesives up to about 20 MPa on the standard joint; order Mark-10's optional low-speed range, because the standard speed range starts above the 1.3 mm/min the test needs. Stronger adhesives need a universal testing machine.

Need a fixture, grips or a complete system for ASTM D1002? Contact Universal Grip with your specimen details, capacity and machine connection and we will quote the right setup.