A method of fabricating a self-locking joint in a panel structure, the method comprising: providing a composite sandwich panel structure comprising at least two face sheets (46a, 46b) and a core portion sandwiched therebetween wherein the core portion comprises a honeycomb core; fabricating in a first portion of the panel structure at least one mortise opening having self-locking end portions (54a, 54b); fabricating on a second portion of the panel structure at least one tenon extension having flexible self-locking members (64a, 64b), wherein the at least one tenon extension: has tapered sides (74a, 74b) adapted for insertion into the at least one mortise opening, and has a size that is greater than a size of the at least one mortise opening such that the flexible self-locking members (64a, 64b) interlock with the self-locking end portions (54a, 54b) in a manner to prevent withdrawal of the at least one tenon extension from the at least one mortise opening, and wherein: the flexible self-locking members (64a, 64b) are designed to have sufficient flexibility and/or deformability that enable them to flex or deform when the tenon extension is inserted into a corresponding mortise opening and that enable them to expand back to their original positions once the flexible self-locking members (64a, 64b) interlock with the respective self-locking end portions (54a, 54b) of the mortise opening, wherein the method further comprises: interlocking the flexible self-locking members (64a, 64b) of the at least one tenon extension with the self-locking end portions (54a, 54b) of the at least one mortise opening to form a self-locking joint in the panel structure. providing a composite sandwich panel structure comprising at least two face sheets (46a, 46b) and a core portion sandwiched therebetween wherein the core portion comprises a honeycomb core; fabricating in a first portion of the panel structure at least one mortise opening having self-locking end portions (54a, 54b); fabricating on a second portion of the panel structure at least one tenon extension having flexible self-locking members (64a, 64b), wherein the at least one tenon extension: has tapered sides (74a, 74b) adapted for insertion into the at least one mortise opening, and has a size that is greater than a size of the at least one mortise opening such that the flexible self-locking members (64a, 64b) interlock with the self-locking end portions (54a, 54b) in a manner to prevent withdrawal of the at least one tenon extension from the at least one mortise opening, and wherein: the flexible self-locking members (64a, 64b) are designed to have sufficient flexibility and/or deformability that enable them to flex or deform when the tenon extension is inserted into a corresponding mortise opening and that enable them to expand back to their original positions once the flexible self-locking members (64a, 64b) interlock with the respective self-locking end portions (54a, 54b) of the mortise opening, has tapered sides (74a, 74b) adapted for insertion into the at least one mortise opening, and has a size that is greater than a size of the at least one mortise opening such that the flexible self-locking members (64a, 64b) interlock with the self-locking end portions (54a, 54b) in a manner to prevent withdrawal of the at least one tenon extension from the at least one mortise opening, and wherein: the flexible self-locking members (64a, 64b) are designed to have sufficient flexibility and/or deformability that enable them to flex or deform when the tenon extension is inserted into a corresponding mortise opening and that enable them to expand back to their original positions once the flexible self-locking members (64a, 64b) interlock with the respective self-locking end portions (54a, 54b) of the mortise opening, wherein the method further comprises: interlocking the flexible self-locking members (64a, 64b) of the at least one tenon extension with the self-locking end portions (54a, 54b) of the at least one mortise opening to form a self-locking joint in the panel structure.