Testing standard
Standard Test Method for Determining Durability of Adhesive Joints Stressed in Shear by Tension Loading
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ASTM D2919 determines the durability of an adhesive joint by holding a single-lap bonded specimen under a sustained tensile shear load while it sits in a chosen environment, and recording the time to failure. Stress, temperature and humidity or immersion are the three variables set deliberately, and a family of failure times across several conditions is what the method is designed to produce. The current edition is D2919-01(2023).
Single-lap adhesive joints are held under a sustained tensile shear load while exposed to a chosen environment, and the time each takes to fail is recorded. The scope covers joints stressed in contact with air, with air in equilibrium with certain solutions, with water, with aqueous solutions, or with other environments, at a range of temperatures. Three variables are set deliberately: applied stress, temperature, and the humidity or immersion condition. The result is not a force but a survival time under those three, and a family of such times across several conditions is what the method is designed to produce.
The premise is stated plainly in the standard: stress and moisture together degrade most adhesive joints, and stress in the presence of water or water vapour can cause some joints to fail at a small fraction of the load needed to break the same joint dry. That is the failure mode a dry lap-shear test cannot see. Two adhesives can post identical breaking strengths on a bench and behave completely differently after a fortnight at load in humid air.
Time to failure falls as stress, temperature and relative humidity rise, which is what makes the method usable as an accelerated screening test. It is also the standard way of separating surface preparation and substrate from the adhesive itself, because those choices show up in durability long before they show up in dry strength. The method notes that assessing an adhesive properly means testing across a range of stress, humidity and temperature, while qualifying one joint for one known service condition may need only a single set.
A durability result belongs to the whole bonded system — substrate, surface preparation, adhesive and cure — not to the adhesive on its own.
Assessing an adhesive properly means testing across a range of stress, humidity and temperature. Qualifying one joint for one known service condition may need only a single set of conditions — but the two are different exercises and should not be confused with each other.
For the dry reference test that sets the stress level, not for the sustained stage. Self-tightening wedges hold a flat adherend squarely; shims or offset grips keep the load line through the bond, since the two strips lie on different planes.
Specifications
Hydraulic closure for the same reference test where the adherends are thick or the joint strong enough that a manual wedge would slip before the bond failed.
SpecificationsTwo different things, at two different stages. Establishing the dry reference strength is a straightforward tension test: a frame with self-tightening wedge or vice-action grips holding the adherends on the load axis, with end shims so the bond line sits on the centreline, run to rupture. That is where a universal testing frame is used, and the set-up is a conventional lap-shear one.
The sustained-stress stage is different. Joints have to hold a fixed load for days or weeks while sitting in a humidity cabinet, a tank of water or an outdoor rack, so they are held in stressing devices rather than in a testing frame — a frame occupied for a month is a frame doing nothing else. What the apparatus must guarantee is that the load stays constant as the joint creeps, and that moving a stressed specimen between environments does not disturb it.
Choosing a stress level too high, so every joint fails within a day and the ranking is dominated by short-term strength rather than durability. Choosing one too low, so nothing fails and the test yields nothing. Reporting a time to failure without the stress, temperature and humidity that produced it, which makes the number meaningless. Comparing durability across two substrate preparations while also changing the adhesive, so neither effect can be attributed. And treating an accelerated result as a service life: the method is explicit that it screens and compares, and the relationship between an accelerated failure time and years in the field is not one this test supplies.
| ASTM D2919 | ASTM D1002 | ASTM D2294 | |
|---|---|---|---|
| Loading | Sustained, in an environment | Ramped to rupture | Sustained, spring-loaded |
| Adherends | Written broadly | Metal to metal | Metal to metal |
| Result | Time to failure | Breaking strength | Creep deformation over time |
| Environment | Chosen deliberately, and a variable | Laboratory conditions | As specified |
| Question answered | How long does this joint last under load and moisture? | How strong is this joint now? | How much does this joint move under a held load? |
| Committee | D14.80 | D14.80 | D14.80 |
A D2919 programme almost always begins with D1002, or its international counterpart ISO 4587, because the sustained stress is set against the dry breaking strength. But dry strength does not predict durability: the method's own premise is that stress in the presence of water or water vapour can cause some joints to fail at a small fraction of the load needed to break the same joint dry.
It is the ASTM test method for determining the durability of adhesive joints stressed in shear by tension loading. Single-lap bonded joints are held under a sustained tensile shear load while exposed to a chosen environment, and the time each takes to fail is recorded. The current edition is D2919-01(2023) — the 2001 text reapproved in 2023 — maintained by subcommittee D14.80, and it is active with no successor named.
Because a dry lap-shear test cannot see the failure mode this method exists for. The standard states its premise plainly: the combination of stress and moisture decreases the durability of most adhesive joints, and stress in the presence of water or water vapour can cause some joints to fail at a small fraction of the load needed to break the same joint dry. Two adhesives can post identical breaking strengths on a bench and behave completely differently after a fortnight at load in humid air.
A time, not a force — and a time that only means something alongside the three conditions that produced it: applied stress, temperature, and relative humidity or the immersion condition. A family of such times across several conditions is what the method is designed to produce. Reporting a time to failure without its conditions makes the number meaningless.
Against the dry breaking strength of the same joint, which is why a set of ordinary lap-shear specimens is broken conventionally first. Choosing the level is the hardest decision in the programme. Too high and every joint fails within a day, so the ranking is dominated by short-term strength rather than durability. Too low and nothing fails and the test yields nothing.
No. The method is explicit that it screens and compares. Time to failure falls as stress, temperature and relative humidity rise, which is what makes it usable as an accelerated screening test — but the relationship between an accelerated failure time and years in the field is not something this test supplies. It ranks candidates and exposes weaknesses; it does not convert to a warranty period.
Because surface preparation and substrate choice show up in durability long before they show up in dry strength. A poorly prepared surface can bond well enough to pass a dry lap-shear test and then fail quickly under sustained load in humid air, since moisture attacks the interface rather than the adhesive. Separating the preparation from the adhesive is one of the method's stated applications — which also means changing both at once in the same programme leaves neither effect attributable.
For part of it. Establishing the dry reference strength is a conventional lap-shear tension test: a frame with self-tightening wedge or vice-action grips holding the adherends on the load axis, with end shims so the bond line sits on the centreline, run to rupture. The sustained-stress stage is different — joints have to hold a fixed load for days or weeks in a humidity cabinet, a tank of water or an outdoor rack, so they sit in stressing devices rather than in a frame. What that apparatus must guarantee is that the load stays constant as the joint creeps, and that moving a stressed specimen between environments does not disturb it.
D2294, Creep Properties of Adhesives in Shear by Tension Loading (Metal-to-Metal), uses the same tension loading on a bonded lap joint but measures creep under a spring-loaded static load rather than time to failure in an environment. It answers how much the joint moves; D2919 answers how long it lasts. D2294 is also written for metal adherends, where the D2919 scope is broader. Both are maintained by subcommittee D14.80 and they are often run in the same programme, but they are not alternatives to one another.
Dak verifies against whichever standard the method names, and where a class applies our frames sit a class tighter than it asks.
| The method asks for | Dak supplies | |
|---|---|---|
| Capacity | The sustained load is a chosen fraction of the dry breaking strength of the same joint, so the reference lap-shear test sets the range. Stress levels are set per programme and none is quoted, no publisher-side figure having been corroborated twice. | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | unknown for D2919 itself; the dry reference test under ASTM D1002 requires ASTM E4 | Verified to ASTM E4, and to ISO 7500-1 Class 0.5 |
| Gripping | Stressing devices that hold the joint at a constant load in the chosen environment for the sustained stage; a tension frame with self-tightening wedge or vice-action grips, and end shims, only for the dry reference strength | Our self-tightening serrated wedge grips, with V-jaws for round specimens or vice-action grips, built to the specimen |
| Environment | Chosen deliberately and varied: air, air in equilibrium with certain solutions, water, aqueous solutions, or other environments, at a range of temperatures | 3009 series chambers, −150 °C to +400 °C — temperature only |
This page describes the method as practised. The governing text is the current edition from the issuing body. Tell us what you are testing and we will answer with the machine, the fixture and a quotation.
