Shear behavior of woven and non-crimp fabric based thermoplastic composites at near-processing conditions

• Published in: Composites. Part B, Engineering Vol. 185; p. 107761
• Main Authors: Mattner, Tobias, Wrensch, Michael, Drummer, Dietmar
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-03-2020
• Subjects: Clamping; Inter-ply shear; Intra-ply shear; Measurement error; Organo-sheet; Organo-sheet; Inter-ply shear; Intra-ply shear; Clamping; Measurement error
• ISSN: 1359-8368; 1879-1069
• DOI: 10.1016/j.compositesb.2020.107761

In intra-laminar shear testing of continuous fiber reinforced thermoplastic composites at near-processing conditions, several factors influence the measured forces in picture frame tests. These influences mostly result from tight clamping of the specimen in the frame and, depending on the heating strategy, possible unmelted areas near the clamping regions, yielding in a shift of the point of rotation of the fibers. An approach to compensate these effects has recently been suggested, but generally valid compensation settings could not yet be deducted. In addition, research on the shear properties of continuous fiber reinforced thermoplastics has been limited to quasi-static deformation speeds and thermodynamically stable temperature levels. This study examines the effect of high deformation speeds and temperature levels in the transitional region between melting point and recrystallization on the intra-laminar shear behavior of different types of continuous fiber reinforced thermoplastics to deduct a material behavior, which better resembles actual processing behavior by using a custom-built picture frame setup. The edge effects are analyzed to deduct generally recommendable compensation settings using a statistical approach. In addition, variations of the pathways of individual fibers in pre-forms are measured, revealing elongation reserves of 0.4–0.5%, which can be confirmed in picture frame tests. The results furthermore show the importance of performing material tests at near-processing conditions to deduct reliable material data for usage in forming simulation. Further research is necessary to understand the complex deformation behavior in the transitional region below melting point and before recrystallization is complete.