Experimental study on the forming limit of unidirectional glass fiber reinforced thermoplastic composites

doi:10.19936/j.cnki.2096-8000.20250328.007

Abstract

Abstract: In this study, the forming limits of unidirectional glass fiber reinforced thermoplastic composites were discussed, aiming to provide a reference for the forming process design and failure behavior prediction. Firstly, the GFRP laminate with a thickness of 1.80 mm was prepared by hot molding with a continuous unidirectional glass fiber reinforced polyamide 6 belt at a ply angle of [0/90]₄. Secondly, the failure modes of the bell specimens and the modified notched specimens were compared based on the Nakajima forming limit test. Finally, the specimen suitable for the study of the forming limit of the GFRP laminate was determined, and the forming performance was characterized by constructing the forming limit curve. The test results show that with the increase of the width of the specimens, the stress state and deformation mode change from uniaxial tensile to biaxial tensile mode. The specimens exhibit three typical failure modes, including fiber tensile fracture, fiber pull-out fracture, and bending-shear coupling fracture modes. The specimens showed the characteristics of brittle fracture, and there was no necking phenomenon before fracture, so the forming limit curve shall be constructed through scatter distribution. Compared with the traditional bell specimens, the notched specimens are more suitable for the experimental study of the forming limit of fiber reinforced composites.

Key words: unidirectional glass fiber reinforced thermoplastic composites, Nakajima test, forming limit curve (FLC), specimen modification, failure mode

CLC Number:

TB332

QI Chang, WU Pengcheng, YING Liang, YANG Shu. Experimental study on the forming limit of unidirectional glass fiber reinforced thermoplastic composites[J]. COMPOSITES SCIENCE AND ENGINEERING, 2025, 0(3): 46-53.

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