Experimental and numerical investigations of interlaminar shear behaviors of CFRP composites at cryogenic and high temperatures

The interlaminar shear strength and failure modes of carbon fiber reinforced polymer composites at different temperatures ranged from 90 K to 353 K were thoroughly investigated by the short beam shear tests. Considering the three different lay-up configurations, i.e., unidirectional, cross-ply and angle-ply, the results showed that the interlaminar shear strength of the unidirectional laminates increased by 67.5 % with the decrease of temperature from room temperature down to 90 K, while they were insignificantly affected by cryogenic temperature for both the cross-ply and angle-ply laminates. A numerical model of short beam shear behavior was developed to calculate the interlaminar shear strength, and the results were found to be in a good agreement with the experimental data. Furthermore, the observations of fracture surfaces using a scanning electron microscope provided the insights into the failure modes of the laminates at the microscopic scale. At 90 K the delamination in the unidirectional laminates was obvious, extending toward to the edge of the specimen. In the cross-ply laminates, a few large penetrating cracks appeared in the mid-plane, several small matrix cracks and voids were obvious in the fracture surface of the specimen. Additionally, the multiple cracks formed by the delamination were observed in the angle-ply laminates.