Effect of voids and crystallinity on the interlaminar shear strength of in-situ manufactured CF/PEEK laminates using repass treatment

Voids and crystallinity, both affected by the temperature history, have an effect on the interlaminar shear strength of thermoplastic composites. In this paper, CF/PEEK laminates with varied porosity and crystallinity are manufactured by repass treatment (based on the laser-assisted forming) under different interlaminar temperature and times of treatment. The porosity and microscopic features of voids are characterized via the water displacement method and optical microscope, respectively. And further squeeze flow of fiber-resin composite and percolation flow of resin occur during repass treatment, which account for the inhabitation of voids. Crystallinity is analyzed through differential scanning calorimetry, which is affected by both cooling rate and recrystallization of the amorphous phase during repass treatment. The interlaminar shear strength of laminates with varied voids and crystallinity is tested, and the failure modes are studied by optical microscope and scanning electron microscope. As a result, the interlaminar shear strength of laminates, with less voids and higher degree of crystallinity, is improved 32.87% than that of the laminates without repass treatment.