Tensile Test Fixture

Concrete reinforced with steel bars is one of the most common materials used in construction. While steel bars provide increased structural integrity to accommodate the tensile stresses in concrete, steel reinforcement is susceptible to corrosion and this deterioration is often not visible and can lead to structural failure.

Various fiber reinforced polymer bars, such as carbon, glass, and basalt fiber reinforced polymer bars are increasingly being used instead of steel bars to reinforce concrete. These fiber reinforced polymer (FRP) materials have a high tensile strength in the direction of the fibers, but are weak in the transverse direction. These materials must be tested for tensile strength via fundamental materials science tests in which a specimen is subjected to a controlled tensile load until failure. This tensile strength test is necessary to quantitatively measure important engineering properties. It is difficult to test FRP materials in tension because the material cannot be clamped directly as this would crush the fibers.

Currently, FRP materials are encased by anchors to be tested with traditional grips (clamping mechanism). Aligning the anchors can be difficult and time consuming, and each specimen requires a dedicated setup procedure for each test run. In addition, the anchors at the specimen end require a large grip opening, often beyond the standard capabilities in certifying laboratories.

An FSU inventor created a tensile test fixture for quick testing of materials with low traverse strength. The novel tensile test fixture can be mounted in any universal testing machine, such as a two-part load frame, and quickly aligned for repeated testing and reliable tensile test results. Alignment of the first test specimen ensures that all consecutive test specimens are identically aligned within the tensile test fixture and no further alignment is required. This novel tensile test fixture greatly improves testing of materials with low strength in the transverse direction.

Advantages

• Works with universal testing machines
• Requires one alignment only
• Does not require each test material to be anchored