Continued advancements in the design and manufacture of engineered composites has allowed composite materials to work their way into the products we use everyday. The most common modern advanced composites are fiber-matrix composites and they can be manufactured with polymer, carbon, metal, or ceramic matrix and an extremely wide range of reinforcement fiber including, carbon, boron, aramid, and glass. Since composites are anisotropic materials, care must be taken in setting up and conducting flexural tests to ensure proper specimen alignment and load application to the test sample. Specimen alignment and orientation may not be as crucial for non-aligned short fiber composites, as many exhibit quasi isotropic behavior. However, non-aligned short fiber composites should still be carefully aligned and tested in multiple orientations to ensure that manufacture processes do not induce undesired fiber alignment.
All aligned fiber composites will exhibit different mechanical properties in different orientations. Flexural tests of composite materials are useful as an alternative or supplementary method to determine tensile and compressive properties. Visual examination of failure behavior and simple bending stress analysis allow the use of flexural strengths to mathematically determine other composite material strength values. Flexural tests are very useful to determine the tensile strength of brittle matrix composites, such as fiber reinforced concrete and fiber reinforced ceramics, since they avoid many of the fixturing difficulties involved in tensile testing brittle materials. Due to the nature of composites, it is often necessary to conduct full-scale component tests along with the testing of composite test sample coupons. The wing break tests conducted by aircraft manufacturers are an example of a full-scale component flexural test. These full-scale tests allow manufacturers to perform validation of computational finite element models and allow the inclusion of irregular geometries and product features that aren't fully characterized with standard test methods.
ASTM and ISO have developed standard test methods for testing composite materials in flexure. The standards provide methods that can be recreated, ensuring materials are tested in the same manner and conditions and allowing test results validation between manufactures and customers. Popular flexural test methods are ASTM C1341 for fiber reinforced ceramic composites, ASTM D2344 for short beam strength of polymer matrix composites and laminates, ASTM D4762 for polymer matrix composites, ASTM D6416 for sandwich composite plates, ASTM D7264 for polymer matrix composites, ISO 14125 for fiber reinforced plastics, and ISO 3597-2 for glass roving reinforced plastics. Articulating rollers are a beneficial feature of loading fixtures for testing the flexural strength of composite materials, as they ensure uniform contact and load application between the loading bars, support bars, and test composite test specimen. Since composite materials are used in a wide variety of environments, flexural test fixtures are also designed to be used in saline baths for testing composites use in marine, biological, and outdoor environments and environmental chambers for composites used in the aviation, aerospace, and automotive industries. The machine families below can be configured to match the load capacities required for composites flexural testing. The bend fixtures have been designed to meets specific ASTM flexural strength test requirements and can also be custom manufactured to meet the unique testing requirements of your composites application. Contact a TestResources application engineer to design the best composites flexural test solution for you.
Applicable Testing Standards
- ISO 3597 Textile-Glass-Reinforced Plastics & Composites Flexural Compressive and Interlaminar Shear Strength
- ISO 14125 Plastic Composites Flexure Bend Test Machine
- ASTM C1341 Flexural Testing for Fiber-Reinforced Ceramic Composites
- ASTM D2344 short-beam testing of polymer matrix composite materials
- ASTM D4762 Polymer Matrix Fiber Reinforced Composites Test Equipment
- ASTM D6416 Flexural Sandwich Composite Plate Composite Test Machine
Recommended Test Machine
Force range of 5 kN to 600 kN (1,125 lbf to 135,000 lbf)
Adjustable test space
The most popular choice for static tension and compression tests
These dual column testers are available in both tabletop and floor standing models
Recommended Testing Accessories
Designed in accordance to ASTM D2344
Free-moving slide supported by rollers for smooth operation
Designed in accordance to ASTM D2344
Adjustable span from 4 mm to 150 mm (0.2 in. to 5.9 in.)
Built-in ruler allows for easy specimen alignment
Designed in accordance to ASTM D7249
Designed in accordance to ASTM D7264
Load ratings of 2.5 kN and 10 kN (550 lbf and 2,250 lbf)
Span and roller dimensions made to order
Satisfies ASTM D790 and D7264
Loading nose is guided by linear bearing for high precision
Standard temperature range of -155°C to 620°C (-247°F to 1150°F)
Accompanied by a broad set of accessories that are capable of withstanding the heat or cold
PID controlled internal temperature
Mounts directly to the test frame
