Comprehensive behavior of <scp>CFRP</scp> laminates with an open hole repaired by prepreg patches in microwave field

Abstract This study presents a CFRP repair technology by laying up the uncured T800 prepreg as a patch followed by curing the patch in a microwave field. The effect of single‐ and double‐sided patches on the comprehensive properties of the repaired panel were studied in detail. Dielectric property tests reveal that T800 prepreg exhibits a higher dielectric constant than the matrix material. The double‐sided sample with 10 layers of patch prepreg in total achieves the highest heating rate of 4.03 °C/min in a microwave field when the microwave power was set at 800 W. FTIR analysis confirms the higher curing degree of the microwave cured sample than the conventional thermal cured sample. The surface roughness of the CFRP panel and the uncured prepreg were measured by a surface profilometer, and the contact angle between the CFRP panel surface and the epoxy resin liquid was obtained to be 48.5°. Compared with single‐sided repair, the double‐sided repair method is suitable for restoring tensile strength due to enhanced mechanical interlocking, wettability, and chemical bonding, and the highest recovery rate of tensile strength reaches 96.9%. However, samples repaired by a single‐sided patch show better recovery of three‐point bending strength than double‐sided samples with the highest recovery rate of 84.1%. Highlights CFRP repair can be achieved by curing the prepreg patch in a microwave field. The microwave heating rate reaches 4.03 °C/min during the repair process. Tensile strength recovery of 96.9% is achieved, reaching 1120 MPa. Bending strength recovery of 84.1% is achieved, reaching 1011.95 MPa.