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The document outlines crucial materials and process considerations for Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM). It covers the properties and procurement of biocompatible constituents like resins, fibers, and cores, emphasizing the control of critical parameters such as viscosity, cure conditions, and tooling techniques. Additionally, it highlights the importance of lay-up, preforming, and thorough inspection processes, ensuring that all materials meet stringent specifications for optimal performance and quality in advanced composite manufacturing.
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Other Product Forms Considerations • RTM and VARTM • Materials (Constituents – resin, fiber, tackifiers, cores, stitches/pins, special forms; also consumable materials) • Processes (Fiber processing, ply cutting, lay-up, preforming, demolding, post-mold operations) • Sandwich • Materials (Constituents – skin, core, adhesives, core splice; also consumable materials) • Processes (Core processing, special details, inspection)
RTM and VARTM Material Considerations • Procurement considerations similar to that of the prepreg material producer • All constituent materials (including fiber sizing, tackifiers, additives, additives, pins, stitching, etc.) need to be controlled via material specs. with out time, packaging, & other critical parameters properly controlled & documented.
RTM and VARTM Material Considerations (cont’d) • Cores, fly-away mandrels (density and stability), consumable/wash-out tooling • Tooling and consumable materials including release agents, cleaning techniques, sealing techniques, bagging materials/bleeders, bagging techniques, and flow media
Neat resin controls are numerous and dependant on material forms Hot melt, heat-activated ingredients, degassed liquid resin, viscosity, visual/color, cure parameters, other parameters Tackifiers Liquid/aqueous and powder Physical parameters (powder size, viscosity), cure parameters, ingredients/chemistry, other Resin compatibility RTM and VARTM Material Considerations (cont’d)
Fiber processing Braiding, specialty weaving, stitching, pinning, hybrids, special forms (T’s, H’s, etc.), automation, consumables Lay-up and Preforming (MOST CRITICAL!)* Special tooling/fixturing for complex shapes Special details (braids, cores, T’s, noodles, etc.) Ply cutting and handling – multi-ply packs/kits Preform locating techniques (tooling pins, features) Tackifiers, pins, stitches, etc. Special tooling/fixtures and processes RTM and VARTM Process Considerations * If the preform is wrong, STOP!
Tool Closure, Injection and Cure Gap measurement, vacuum check, bag check Resin injection/infusion sequence/cycle Critical heating areas, heat-activated ingredients/cure agents (preform=filter) Heat-up Vacuum (hard) Inject/infuse resin Bleed technique/sequence, bag check Ramp-up, back pressure Plumbing diagram (consumable plumbing, preheater) RTM and VARTM Process Considerations (cont’d)
Demolding Mandrel extraction - critical sequences Wash-out mandrels Tooling holes/fixturing features Neat resin sample or witness laminate Tool cleaning and prep Post-molding Operations Typical but usually more complex RTM and VARTM Process Considerations (cont’d)
Sandwich Material Considerations • Generally the same as hand lay-up • Core control/core storage and preparation • Core orientation – L & W (&Z) properties • Core corrosion control/treatment • Core splice and other materials • Bleeders and other consumables • Resin flow parameters criticality – determines fillet characteristics/strength
Sandwich Process Considerations • Similar to hand lay-up • Core handling, core cutting • Special details/hard points – bond prep and location features • Orientation - L, W & Z directions • Core forming & core splice • Cure parameters • Inspection – Coin-tap? Other testing?
