Influence of gripping method on tensile properties of unidirectional thermoplastic CFRP – Round-robin activity for international standardization in Japan:

For unidirectional thermoplastic composite materials, it is preferable to use tab-less specimens in tensile tests owing to the low adhesive performance between specimens and tabs, as well as considerable warpage in laminates due to compression molding. In this study, round-robin tests are performed for unidirectional laminates in the 0 degrees and 90 degrees directions by two types of thermoplastic composites - carbon/polyamide 6 and carbon/polypropylene. The purpose of the round-robin test is to examine the difference between tab-bonded and tab-less specimens. Statistical analyses determined the degree to which tab-less specimens influenced their evaluation of the mechanical performance. In addition, from the detailed experiments, precisely controlled gripping force, fine roughness of grip surfaces, and a few inserted abrasive papers had significant impact on the 0 degrees tensile strength of tab-less specimens. Based on the results, 0 degrees tab-less strength of the proposed gripping method was shown to be almost equal to that of tab-bonded specimens recommended by the present tensile test standard.