ASTM D3846 describes the method for determining the in-plane shear strength of reinforced plastic composite materials. These specimens are typically thermosetting plastics with reinforcements that widely vary in type and thickness ranging from 2.54 mm to 6.60 mm.
The test method is similar to that of ASTM D695-15 Test Method for Compressive Properties of Rigid Plastics, except that in the ASTM D3846 method, failure of the specimen occurs in shear between two centrally located notches that are machined halfway through the thickness of the specimen and spaced a fixed distance apart on opposing faces. For this test, we recommend a 6800 Series universal testing system.
The challenges of testing to this standard:
- Ensuring parallelism of compression platens
- Reporting calculations in compliance with the standard
- Ensuring parallelism of compression platens – When testing according to ASTM D3846, the compression platens must be parallel to each other and in the normal plane to the axial loading. The lockable spherically-seated platens provide a means of pre-loading the assembly and locking the platen to ensure parallelism for the test.
- Reporting calculations in compliance with the standard – In order to calculate the in-plane shear strength, the user must measure the length of the failed area. Bluehill® Universal materials testing software offers a prompted test to walk users through the necessary inputs at each step. An integrated specimen measurement device can be used to automatically input the measurements into Bluehill Universal, saving time and eliminating typos.
It is important to review ASTM D3846-08(2015) in order to fully understand the test setup, procedure, and results requirements.