Abstract: A material composition and method for making flexible inversion liners having glass fibers added for strength is disclosed. The liner combines a first layer of polyester felt, an open-faced knit of fabric from ECR glass and PET strands, glass fibers, and a second layer of polyester felt. These components are needle-punched together into essentially a single composite mat, or substrate, using standard needle-punching machinery. The liner is then formed into a tube preferably through a butt joint and prayer stitch covered with a urethane tape. A coating or foil is placed on the outside (prior to inversion) of the liner that is then impregnated with resin. For heat curing, the liner is impregnated with a thermosetting or UV-cured resin. The liner is then installed in a pipe through inversion, using either air or water and cured with UV, steam, or hot water.