Page 87 - Engineered Interfaces in Fiber Reinforced Composites

IO Engineered interfaces in jiber reinforced composites

The technique underlying this test has the advantage of utilizing the relatively
inexpensive, straight-sided tensile specimens and conventional uniaxial tensile test
equipment. Caution should be exercised, however, in interpretation of the ultimate
shear strength values obtained from this test because the laminate is under combined
normal and shear stresses. Nevertheless, there is generally a good agreement
between the stress-strain response obtained in this test and other in-plane shear test
geometry including the three-rail shear (Sims, 1973) and the torsion shear tests
(Chiao et al., 1977).

3.3.5. [lo"] of-axis tensile test

The [lo"] off axis tension specimen shown in Fig 3.23 is another simple specimen
similar in geometry to that of the [f45"], tensile test. This test uses a unidirectional
laminate with fibers oriented at 10" to the loading direction and the biaxial stress
state (i.e. longitudinal, transverse and in-plane shear stresses on the lo" plane)
occurs when it is subjected to a uniaxial tension. When this specimen fails under
tension, the in-plane shear stress, which is almost uniform through the thickness, is
near its critical value and gives the shear strength of the unidirectional fiber
composites based on a procedure (Chamis and Sinclair, 1977) similar to the [f45"],
tensile test.

Fiber
direction

Fig. 3.23. Schematic drawing of specimen for [IO"] off-axis tensile tcst. After Chamis and Sinclair (1976).