MIL-HDBK-17-1F Volume 1,Chapter 5 Prepreg Materials Characterization b.The length of any portion of the gap with an average width of 0.030 inch(0.76)should not exceed 24 inches (0.61 m). c.Gaps in line with each other and no more than one inch(25 mm)apart should be considered as one gap,regardless of number. d.Gaps with excessive width or length should be considered defective and will be the basis for flag- ging or replacing the prepreg. 5.4.1.3 Width Width tolerance for unidirectional prepreg tape should be as specified,typically t0.030 inch(0.76 mm). 5.4.1.4 Length The length of each roll of prepreg should be provided.Limits on the length of prepreg on any single roll should be specified.Alternatively,suppliers and users may agree on limits for the prepreg weight or area per roll. 5.4.1.5 Edges Acceptable waviness of edges should be specified.A typical acceptance value for any 12-inch(30- cm)length of tape should be 0.030 inch(0.76 mm)from the edge when measured with an appropriate straight edge 5.4.1.6 Splices Prepreg splices may be permitted on any roll of tape where processing is continuous without change in fiber or resin batch.Such splices should be appropriately marked as a nonconforming area. 5.4.2 Resin content The resin content of prepregs may be determined by extracting the resin from the prepreg fibers us- ing a solvent in which the resin material is fully soluble and the fibers are not dissolved.Soxhlet extrac- tion procedures are described in ASTM C 613(Reference 5.4.2(a)).Procedures for determining the resin content of carbon fiber-epoxy prepregs are provided in ASTM D 3529(Reference 5.4.2(b)).Special pro- cedures and solvents may be required to extract high molecular weight or thermoplastic resins.An alter- nate procedure for determining the resin content in epoxy resin prepregs is outlined in Section 5.5.1. 5.4.3 Fiber content Procedures used to determine resin content often provide information about the fiber content of pre- pregs.Alternatively,acid digestion methods(ASTM D 3171)may be applied to remove the matrix resin from the fibers as long as the fibers are not degraded(Reference 5.4.3).Digestion methods are not pre- ferred for graphite and aramid fiber prepregs since such fibers are subject to oxidative degradation.Sec- tion 5.5.1 describes a procedure for determining the fiber and resin contents of glass,carbon,and aramid fiber/epoxy resin prepregs. 5.4.4 Volatiles content The volatiles content of prepregs may be determined by ASTM D 3530(Reference 5.4.4).Thermo- gravimetric analysis(TGA)may also be applied to estimate weight percent volatiles in a prepreg. 5-3MIL-HDBK-17-1F Volume 1, Chapter 5 Prepreg Materials Characterization 5-3 b. The length of any portion of the gap with an average width of 0.030 inch (0.76) should not exceed 24 inches (0.61 m). c. Gaps in line with each other and no more than one inch (25 mm) apart should be considered as one gap, regardless of number. d. Gaps with excessive width or length should be considered defective and will be the basis for flag￾ging or replacing the prepreg. 5.4.1.3 Width Width tolerance for unidirectional prepreg tape should be as specified, typically ±0.030 inch (0.76 mm). 5.4.1.4 Length The length of each roll of prepreg should be provided. Limits on the length of prepreg on any single roll should be specified. Alternatively, suppliers and users may agree on limits for the prepreg weight or area per roll. 5.4.1.5 Edges Acceptable waviness of edges should be specified. A typical acceptance value for any 12-inch (30- cm) length of tape should be 0.030 inch (0.76 mm) from the edge when measured with an appropriate straight edge. 5.4.1.6 Splices Prepreg splices may be permitted on any roll of tape where processing is continuous without change in fiber or resin batch. Such splices should be appropriately marked as a nonconforming area. 5.4.2 Resin content The resin content of prepregs may be determined by extracting the resin from the prepreg fibers us￾ing a solvent in which the resin material is fully soluble and the fibers are not dissolved. Soxhlet extrac￾tion procedures are described in ASTM C 613 (Reference 5.4.2(a)). Procedures for determining the resin content of carbon fiber-epoxy prepregs are provided in ASTM D 3529 (Reference 5.4.2(b)). Special pro￾cedures and solvents may be required to extract high molecular weight or thermoplastic resins. An alter￾nate procedure for determining the resin content in epoxy resin prepregs is outlined in Section 5.5.1. 5.4.3 Fiber content Procedures used to determine resin content often provide information about the fiber content of pre￾pregs. Alternatively, acid digestion methods (ASTM D 3171) may be applied to remove the matrix resin from the fibers as long as the fibers are not degraded (Reference 5.4.3). Digestion methods are not pre￾ferred for graphite and aramid fiber prepregs since such fibers are subject to oxidative degradation. Sec￾tion 5.5.1 describes a procedure for determining the fiber and resin contents of glass, carbon, and aramid fiber/epoxy resin prepregs. 5.4.4 Volatiles content The volatiles content of prepregs may be determined by ASTM D 3530 (Reference 5.4.4). Thermo￾gravimetric analysis (TGA) may also be applied to estimate weight percent volatiles in a prepreg