ASTM D5868
Lap Shear Grips for FRP and Plastic Bonding (also ASTM D3163)
Request ASTM D5868 Lap Shear Grip Specifications
ASTM D5868 measures the lap shear strength of adhesives used to bond fiber-reinforced plastic (FRP) to itself or to metal, and ASTM D3163 does the same for rigid plastics. Both use a single-lap joint pulled in tension. Universal Grip supplies wedge or screw-action grips with offset spacers so the bond line stays on the load axis, the same proven setup we build for ASTM D1002 metal lap shear.
What ASTM D5868 Measures
The tests report the failure load and the apparent shear strength, the peak force divided by the bonded area, along with the failure mode: adhesive, cohesive or substrate. Automotive, marine and composite manufacturers use D5868 to qualify structural adhesives and surface preparation; D3163 is used for bonded thermoplastic and thermoset parts.
How the ASTM D5868 Test Works
Bond two adherends, typically 25.4 x 101.6 mm (1 x 4 in), with a 25.4 mm overlap (12.7 mm is also used).
Cure the adhesive as the manufacturer specifies.
Clamp each end in a grip, using shims or offset jaws equal to the adherend thickness so the joint is centered.
Pull at the specified rate: 13 mm/min (0.5 in/min) for D5868, 1.3 mm/min (0.05 in/min) for D3163.
Record peak force, calculate shear strength and classify the failure.
Specimens and Setup
Use spacers or offset jaws so the load line passes through the bond line and the joint is not bent at the start.
Wipe off adhesive squeeze-out so the overlap area is well defined.
Grip far enough from the overlap that the jaws do not crush the bond.
Report the failure mode; a substrate failure means the adhesive is stronger than the FRP or plastic.
Confirm specimen size and test rate against your copy of the current standard.
Universal Grip ASTM D5868 Fixture
Wedge or screw-action grips sized for 25 mm wide adherends
Offset jaws or shims to center the single-lap joint
Serrated or smooth faces to suit FRP and plastic surfaces
Self-aligning clevis connection to reduce bending
Capacities to suit structural adhesives
Clevis pin or threaded adapters for your frame
Applications
Automotive FRP and SMC bonding
Marine and composite assembly
Plastic part bonding
Surface preparation studies
Related Standards and Products
Send us your specimen dimensions, required capacity and machine connection through our contact page and we will quote an ASTM D5868 lap shear grip set. Request a quote
ASTM D5868 FAQ
How is D5868 different from D1002?
D1002 is for metal-to-metal lap joints. D5868 covers fiber-reinforced plastic bonded to itself or to metal, and D3163 covers rigid plastics. The grips and joint style are similar, but test rates and adherends differ.
What test speed does D5868 use?
D5868 uses 13 mm/min (0.5 in/min). D3163 is much slower, at about 1.3 mm/min (0.05 in/min).
Why are shims or offset jaws needed?
A single-lap joint has its adherends offset by their thickness. Shims or offset jaws line the bond up with the load axis so the joint is not bent before testing.
What if the FRP breaks before the bond?
That is recorded as a substrate failure. It shows the adhesive bond is stronger than the adherend, which is often the goal of the test.