User:FuzzyMagma/Arcan test fixture

The Arcan test fixture is a testing device used to determine the mechanical properties of materials, such as metals, plastics, composites, and fiber-reinforced polymers (FRPs). The test method involves applying a shear force through a section between two edge notches to produce a nearly uniform shear stress along the section. The Arcan test fixture consists of a specimen holder that mounts the test coupon and a testing machine that applies the load. The fixture can be used for uniaxial and biaxial testing of laminates in pure shear and combined normal/shear stress states.

The Arcan testing configuration has been successful in testing a wide range of materials. There are typically two classes of methods used to attach the Arcan fixture to the load frame actuators: a connection allowing rotation in the plane of the specimen and a "fixed" connection inhibiting in-plane rotation at the fixture ends. Modified versions of the Arcan test fixture have been developed to produce different biaxial states of stress by varying the angle α between the longitudinal axis of symmetry of the specimen.

Examples of research papers and video

The Arcan test fixture is a testing device used to determine the mechanical properties of materials, such as metals, plastics, composites, and fibre-reinforced polymers (FRPs). The Arcan test fixture was originally designed by Arcan et al. in 1978 to evaluate the inter-laminar fracture parameters under complete in-plane loading conditions, ranging from pure mode I to pure mode II, with a single specimen configuration. The test method involves applying a shear force through a section between two edge notches to produce a nearly uniform shear stress along the section. The Arcan test fixture consists of a specimen holder that mounts the test coupon and a testing machine that applies the load. The fixture can be used for uniaxial and biaxial testing of laminates in pure shear and combined normal/shear stress states. The Arcan testing configuration has been successful in testing a wide range of materials.

There are typically two classes of methods used to attach the Arcan fixture to the load frame actuators: a connection allowing rotation in the plane of the specimen and a "fixed" connection inhibiting in-plane rotation at the fixture ends.

Modified versions of the Arcan test fixture have been developed to produce different biaxial states of stress by varying the angle α between the longitudinal axis of symmetry of the specimen.

Further modifications, of the Arcan fixture, proposed by Yen et al. included bolting a butterfly-shaped specimen between two symmetrical semi-circular steel discs. The specimen had trapezoidal cut-outs into which it was fitted before bolting it down. Yen showed that a homogenous stress and strain fields can be obtained through a central butterfly-shaped specimen. This was also the origin of the test specimen known today as the “butterfly specimen”. This was certified with a photo-elastic analysis.

A problem that exists with the current optimized butterfly specimen is that the stress concentrations on the inner circular edges are responsible for early fractures due to the uniaxial stresses acting in the notches/defects present after manufacturing of such a specimen.

In 1995 the Arcan fixture was modified by Amstutz et al. for more stable crack opening. Instead of using trapezoidal cut-outs Hajjar and Ali increased the number of bolts used, six bolts for each side of the specimen, to fasten the specimen to the Arcan. These alterations allowed for biaxial stresses to be obtained with relative ease by adjusting the (α) angle at which the loads are applied.

It is normally assumed that for unidirectional materials that the in-plane and through-thickness mechanical properties are the same for both the transverse and shear directions if a homogenous stress field exists within the test specimen.