Exploring the influence of specimen types on the intralaminar fracture behavior of fiber-reinforced polymer matrix composites

The accurate determination of fracture toughness of fiber-reinforced composites is critical for the assessment of structural integrity. Although there have been many studies on the intralaminar fracture behavior of composites, satisfactory results have not yet been obtained regarding the influence of specimen types. In this paper, commonly used fracture specimens (DCT, CT, ESET, pin-loaded SENT and clamped SENT specimen) are applied to study their applicability in the fracture behaviors of composites with different orientations. And the impact of data processing methods for the area method, G_C-compliance and G_C-stress intensity factors on fracture performance was analyzed. The results showed that the above three data processing methods have obtained relatively consistent fracture properties. Different specimens obtained significantly various results, showing a gradually decreasing trend from clamped SENT, ESET, pin-loaded SENT, CT to DCT. Furthermore, considering that the clamped SENT specimen is closest to the Mode-I fracture toughness obtained from the DCB specimen, and there is no compression damage in the experiments under different orientations, this specimen type is the most recommended specimen. Finally, the failure mechanisms of carbon fiber-reinforced composite under different specimen types and orientations were revealed. As the orientation angle increases (β from 0° to 90°), the failure mode gradually transitions from matrix cracking and interface debonding to matrix shear and fiber fracture. The above achievements will contribute to a deeper understanding of the intralaminar fracture process and failure mechanism of fiber-reinforced composites.