A biaxial tension device (Fig. 7.2) has also been used to characterize the tensile behavior of the reinforcements.

The biaxial tension device.

Biaxial and uniaxial tension tests as well as tensile test conducted on individual tows can be performed using this device. In-plane shear test can also be performed using the bias test samples. All these specific samples are shown in Fig. 7.3. For synthetic carbon or glass fabrics, the limit to failure is not reached during form­ing, and the tensile test are designed to analyze the possible nonlinearity of the stress-strain curves due to the 2D assembly of the woven textiles generally used. For natural fiber fabrics, the tensile limit of the fabric becomes particularly interesting as the tows used to elaborate the woven fabrics are manufactured from finite length
fibers slightly entangled and held together by a natural binder are not expected to show comparable tensile resistance. The tensile strains for each considered tows are measured using a 2D version of the mark-tracking device described previously. The detailed description of the device as well as the procedure of the test may be found in Reference 67.