Overview
ISO 15034:1999 - Composites - Prepregs - Determination of resin flow specifies a laboratory method to measure the amount of resin that flows (bleeds) from continuous-fiber prepregs during cure. The standard applies to prepregs impregnated with epoxy and/or unsaturated polyester resins and defines specimen preparation, apparatus, conditioning, cure procedure and result expression. The test quantifies resin flow as the percentage mass difference before and after cure (with an optional correction for volatile matter).
Key Topics and Technical Requirements
- Specimen geometry: Cut 100 mm × 100 mm pieces using a metal/ceramic template; assemble plies to obtain 0.2–0.5 mm thickness (typical 2–4 plies). Avoid selvedges; cut across prepreg width unless agreed otherwise.
- Apparatus: analytical balance (±1 mg), heated platen press (up to 200 °C and 600 kPa), glass bleeder cloth (181 style or equivalent), perforated and unperforated release films, cutting knife.
- Assembly & cure: Sandwich the test specimen between perforated release film and bleeder cloth with unperforated release film on outer faces. Insert into a press preheated to the agreed cure temperature and apply a uniform pressure of 400–600 kPa (reach set pressure within 5 s). Hold until cure is sufficient to handle.
- Weighing & calculation: Weigh specimens before and after cure to 1 mg precision. Resin flow is expressed as percent mass loss (or percent difference) and can be corrected for volatile content when required (volatile content measured per ISO 9782).
- Repeatability: Test at least three specimens per sample. The standard notes that interlaboratory precision data are not yet available.
- Environment & handling: Condition and test in standard atmospheres per ISO 291. Prepregs are typically stored cold (around −18 °C); avoid moisture pickup and condensation when opening packages.
- Reporting: Include identification, number of plies, cure temperature/pressure/time, individual and average results, materials used (bleeder cloth, release films) and test date.
Applications and Users
ISO 15034 is used by:
- Prepreg manufacturers for product development and quality control
- Composite process engineers assessing resin bleed/flow characteristics for tooling and layup design
- Aerospace, automotive, marine and sporting-goods manufacturers validating cure behaviour
- Third‑party testing labs providing material data for procurement and certification
Testing helps prevent excessive resin bleed that can affect fiber wet-out, void content, tool contamination, and final laminate properties.
Related Standards
- ISO 291 - Standard atmospheres for conditioning and testing
- ISO 472 - Plastics vocabulary
- ISO 8604 - Prepreg definitions and symbols
- ISO 9782 - Determination of volatile-matter content (used to correct resin‑flow results)
Keywords: ISO 15034, resin flow, prepregs, composites testing, prepreg resin bleed, epoxy prepreg, unsaturated polyester, cure testing, heated platen press.
