An evaluation of damage development for CFRTP by conventional tows and spread tows using acoustic emission

Comparison of damage development of textile composites made by combination of two resin (Polyamide and Epoxy) and two kinds of fiber bundles (conventional tows and spread tows) is carried out. The quasi-static tensile tests were carried out with using DIC (digital image correlation) system to estimate the full field strain and AE (acoustic emission) sensors for measurement of the acoustic emission features. The CFRTP specimens were also investigated with optical microscope to clarify the difference of damage. Fig.1 shows characteristic damage of each CFRTP. The fiber debonding and delamination were shown in CF(with spread tows)/PA composites and the damage in weft yarn covered a wide range of test specimens. It is suggested that these features of damage were influenced with effect of fiber opening. This may also be explained by AE events. In weft yarn of CF(with conventional tows)/PA composites, we observed not only transverse crack but also clack which propagated parallel to loading direction. This type of crack was not found in other thermoplastic carbon composites such as CF/PPS described in the literature. From these results, we conclude that the damage development of textile composites is sensitive to the form of fiber bundles and the properties of the matrix.