Honeycomb composites, also know as sandwich core composites, are a unique form of composites. They are made up of an inner core that is made of thin light material positioned on a honeycomb shape, and an outer laminate that is bonded to the honeycomb. Honeycomb composites rely on the geometry of the fabricated materials for its strength. The outer material provides stiffness to the honeycomb composite. The adhesion between the outer material and the inner honeycomb increases the bending strength of the composite by distributing the bending load to a tension-compression load in the honeycomb. In applications that rely on the bending strength honeycomb composites, understanding the strength of the adhesive bond between the top layer and inner layer is critical. Shear fatigue tests are often used to gain understanding into the endurance capabilities of the top layer and inner honeycomb layer. By compressing the composite ASTM C394 is a test method used to determine the fatigue shear strength sandwich core materials. This standard test method takes a strip of sandwich core composite and bonds it to a set of grips that move axially along the direction of the outer layer. TestResources suggests either a servo hydraulic or servo electric t dynamic testing machines for fatigue testing materials. Servo hydraulic test machines, such as the 902 series has high load capabilities up to 22 kip and high cyclic frequency capacity up to 100 Hz. Servo electric test machines, such as the 830 and 810 series, have lower load capacity and lower speed capacity then the servo hydraulic models. However, this makes them much less expensive then the servo hydraulic test machines and just as capable in terms of meeting the requirements of ASTM and ISO strain controlled fatigue testing standards. There are a wide variety of controllers that can be used with the dynamic test machines. GC 273 are excellent grips for adherence fatigue testing materials in shear.
Applicable Testing Standards
- ASTM C365 Compression Sandwich Core Flatwise Test Machine
- ASTM C394 Shear Fatigue - Sandwich Core Materials
- ASTM E466 Load Controlled Constant Amplitude Fatigue Tests of Metals
Recommended Test Machine
Static and fatigue forces up to 50 kN (11,250 lbf)
Frequency ratings up to 75 Hz
Oil-free, all electric actuator for clean test conditions
Lower purchase, operating, and maintenance costs than hydraulic equivalents
Static and fatigue forces up to 25 kN (5,500 lbf)
Frequency ratings up to 100 Hz
Servohydraulic
Small, portable footprint
Recommended Testing Accessories
Designed in accordance to ASTM C273