A library of knowledge that contains a fabric database, 3D human body models database, and 3D garment database has been developed in the framework of the Erasmus+ project DigitalFashion – “Collaborative Online International Learning in Digital Fashion”, which is a collaboration of 6 European partners who would like to strengthen their working together through collaboration in online international teaching. The fabric database contains 49 physical textile fabrics, both woven and knitted fabrics. Each partner provided at least eight fabrics. The library contains also 3D human body models of different sizes (male, and female), and 48 pattern designs for women’s and men’s garments. The fabric’s physical and visual parameters have been determined using known textile standards, including their draping images taken using a Cusick Drape Tester. These fabric parameters have been used to predict the equivalent digital twin fabric based on Lectra digital fabrics, thereby completing the fabric database with their matching digital twin fabric. The digital twin fabrics have been used to simulate the 3D garments for the 3D garment database, based on the selected patterns and styles. To test the robustness of the fabric digitization process, a woman A-line skirt (real) was made by each partner using their fabric. These skirts were then compared with their simulated (virtual) skirts. The investigation has shown that the digital twin fabrics represent the real fabrics well. The virtual training library will support the specially developed training platform for virtual fashion design.