Standard Test Method for Shear Properties of Sandwich Core Materials
APP-C273Always sandblast and solvent-wipe the steel loading plates to bare metal immediately before applying epoxy to prevent premature bond line peeling.
Challenge & Testing Gap
Parasitic bending and peeling moments generated by thick bonding plates distort pure planar shear states inside the core.
The Solution
Utilize , precision-ground steel loading plates paired with self-aligning knife-edge or universal joint frame adapters.
Mechanics & Specimen Behavior
Primary Mechanics
Planar shear loading applied parallel to the sandwich plane via rigid plates bonded to the core faces until core failure.
Specimen Details
Rectangular block of core material bonded between two thick steel or aluminum loading plates per standard thickness.
Mechanical Ratios & Properties
Length-to-thickness ratio fixed to a minimum of 12:1 to ensure a uniform shear stress distribution across the free core span.
Expert Engineering Commentary
Core Problem Identification
Adhesive bond line failure at the plate interface before achieving true ultimate shear failure within the core.
Root Cause Analysis
Inadequate surface preparation or improper selection of the high-strength structural adhesive used for plate bonding.
Hardware Specific Solutions
Heavy-duty dual-plate shear testing fixture with heat-treat hardened alignment tracking pins and low-friction universal joints.
Analysis & Calculation Standards
Event & Failure Detection
Initial non-linear seating detection followed by continuous first-derivative load drop tracking at ultimate core rupture.
Required Calculations
Core Shear Strength, Core Shear Modulus, Shear Strain at Break, Peak Force, and Failure Mode (Core vs Adhesive).
Statistical Outputs
Batch mean values, standard deviation, and variance envelopes for core density and shear properties correlation.
32-bit closed-loop Newton controller monitors plate-travel micro-displacements directly to calculate precise core shear strain.
Additional Commentary
Proper load alignment completely eliminates external bending moments, forcing pure, unadulterated planar shear stress.
Ensure the line of action of the applied force passes directly through the diagonally opposite corners of the sandwich core.
Common Pitfalls
Using an elastic epoxy that is too flexible, which introduces secondary compliance errors into the core shear modulus calculation.