On correlation of stamping process with fiber angle variation and structural performance of thermoplastic composites

This study aims to experimentally explore the influences of stamping conditions on the variations in fiber yarn angle and material properties of continuous fiber reinforced thermoplastics (CoFRTP). First, the upright-orthogonal (O-), biased-orthogonal (B-) and non-orthogonal (N-) specimens were manufactured with thermo-stamping process. Second, the X-ray computed tomography (CT) was employed to characterize fiber yarn angle variations within each layer of thin-walled CoFRTP structures nondestructively. The results indicate that fiber yarn angle varied in different layers at the same position and also changed at different positions in the same layer for the N-specimens. In addition, the 6-ply, 8-ply and 10-ply N-specimens exhibited a similar average variation in fiber yarn angle. Finally, the tensile and three-point bending (TPB) tests were conducted to investigate the effects of stacking sequence and fiber yarn angle variations on material properties and structural performances of these cured CoFRTP specimens. In the off-axis tensile tests, the modulus, yield strength and failure strength of laminates decreased but the failure strain increased with increasing fiber yarn angle. In the TPB tests, the O-specimen showed the smallest failure displacement, the B-specimen presented the highest peak force, and the N-specimen exhibited the largest failure displacement. This study is anticipated to gain insights into the relationship between stamping process and forming characteristics as well as structural performances of CoFRTP structures. • Quantitative characterizations of fiber yarn angle variations. • Empirical formulas between fiber yarn angle variations and mechanical properties. • Correlations between the stamping process and structural performances.