What informs you about the number of plies required and their orientation in the lay-up process?

The correct answer is planning papers because these documents provide critical information regarding the specific requirements for a composite lay-up process. Planning papers detail the number of plies needed as well as their orientation, which is vital for achieving the desired structural integrity and performance of the composite part. This documentation is based on the engineering design criteria and testing results that outline how the materials should be laid up to meet safety and performance standards in aerospace applications.

While instruction manuals and project blueprints may offer general guidelines on procedures and overall design, they do not typically specify the intricate details of ply requirements and orientations like planning papers do. Material specifications inform about the properties and characteristics of materials used, but they do not directly address lay-up processes or ply orientation. Thus, planning papers are the primary source of information for this specific aspect of composite fabrication in aerospace.