The present invention is to provide methods to increase composite interlaminate strength and interface strength, and make 3D fibers products, prepregs and composites, by using trans-interface and/or trans-fiber products such as trans-plies, strands and/or yarns fastening components selected from the group comprising of hooks and loops (velcro), hooks and hooks, zipper heads, fish hook shape hooks, staples, arrow heads, forks and mushroom heads. One ply of fibers has one or multiple of the above fasteners on at least one side. Lay-up the plies with said fastening components on its one or two sides to obtain a 3D fiber products with those fastening components locked together. The plies can be separated if need re-lay-up. A thread or a yarn have the fastening components around 0-360 degree on its surface. Lay the threads together or intercross each other to get a 3D fiber products. In those 3D fiber products, two parts of the fastening components lock each other if they meet and engage. A 3D composite can be made using the 3D fiber products.
One fiber ply with the fasteners on its at least one side, is impregnated or protruded with matrix materials, a piece of the prepreg with the fasteners prepreg with the fasteners are made. Lay and press the prepreg together fastening components will lock each other if they meet and engage. In most of production processes, the matrix materials might soften and meld, and the fastening components will further interlock each other. So a 3D composite structure is made by the said 3D prepregs. Those fastening components may stay just partially or fully in matrix at matrix surface. The fastening components increase the interface strength when two matrix materials meet just by crossing interface even if they are not locked and without fiber products in matrix.