Composites power lighter, stronger airframes, missiles, radomes, and space structures, and the layup method decides how well those parts perform. This guide explains the Top 10 Aerospace and Defense Composite Layup Techniques in clear language, from factory floor practices to advanced automation. Each technique focuses on how to place plies, control resin, reduce defects, and improve repeatability while meeting strict aerospace specifications. You will learn what the method is, when to use it, and which controls matter for quality. With these fundamentals, engineers, technicians, and buyers can speak the same language, speed certification, and produce reliable, inspection ready composite hardware.
#1 Automated fiber placement
Automated fiber placement uses multiple narrow tows delivered through a compaction head that steers along complex paths. Success depends on tow tension, head temperature, nip force, and accurate path planning to limit gaps and overlaps. Use small steering radii only within machine limits to avoid wrinkling. Program stagger patterns to prevent resin rich lines. Apply in situ inspection with vision or laser sensors to measure placement quality. For thermoplastics, keep melt temperature uniform and consolidate each course consistently. For thermosets, plan debulk intervals, maintain vacuum integrity, and track material out time so that production remains repeatable across shifts.
#2 Automated tape laying
Automated tape laying places wider tape to build large skins, fairings, and covers quickly on gentle curvature. Keep tape tension constant and control head temperature so adhesive tack stays stable during placement. Plan course boundaries to avoid butt joints lining up between plies. Use laser projection to guide operators and verify course numbering. Add periodic debulk cycles to compact air and stabilize geometry before the next stack. On contoured tools, limit steering angles and employ cut and restart strategies where curvature would cause bridging. Validate thickness with ultrasonic checks and record machine data for process capability studies.
#3 Hand layup with ply book discipline
Hand layup remains essential for prototypes, repairs, and complex details. Start with a clean, climate controlled area, dedicated tools, and labeled ply kits. Follow a detailed ply book showing orientation, reference datums, and sequence numbers. Handle prepreg with gloves, minimize stretching, and place each ply from datum outward to reduce cumulative error. Roll edges gently to remove trapped air, and avoid wrinkles at radii using tailored darts or segmented plies. Debulk on schedule with proper bleeder and breather to keep resin balance consistent. Build a robust vacuum bag stack and add pleats to prevent bridging at corners.
#4 Hot drape forming and membrane forming
Hot drape forming softens prepreg with radiant or contact heat, then compacts it onto the tool using a flexible membrane. This allows smooth placement over double curvature while limiting fiber wrinkling. Preheat within the recommended window so resin is tacky but not runny. Preform complex plies on forming tools, then transfer to the main mold to improve alignment. Use controlled debulk to freeze shape before continuing the stack. Monitor spring back and adjust compensation in flat patterns. Add localized intensifiers at tight radii, and verify that ply edges remain fully compacted to avoid porosity during cure.
#5 Sandwich layup with honeycomb or foam cores
Sandwich panels deliver high stiffness to weight by bonding skins to a lightweight core. Kit the core precisely, splice with approved adhesives, and keep vent paths open so air escapes during cure. Use film adhesive or co-cure the first skin to the core with uniform pressure. Pot around fastener inserts and edge close outs to block moisture paths and improve bearing strength. Avoid bridging over cell walls by applying light compaction before full vacuum. Control core moisture with bake out when needed. Verify bondlines using tap testing or ultrasonics, and document adhesive coverage for every panel.
#6 Out of autoclave layup and infusion
Out of autoclave methods include OOA prepregs, vacuum assisted resin transfer molding, and resin infusion. For infusion, select fabrics and cores with the right permeability, position flow media, and define resin breaks to prevent race tracking. Control vacuum leak rates and ensure consistent bag contact across the mold. Stage temperatures to lower viscosity for wet out, then ramp to gel and cure without excessive exotherm. For OOA prepregs, follow venting guidance, execute intermediate debulks, and maintain oven airflow for uniform heat. Validate porosity targets with ultrasonic attenuation maps and correlate them with process parameters for improvement.
#7 Co curing, co bonding, and secondary bonding
Structural integration can reduce fasteners and weight when surfaces are bonded during or after cure. For co curing and co bonding, confirm resin and adhesive compatibility, set bondline thickness using scrim or calibrated shims, and manage exotherm at intersections. For secondary bonding, surface preparation is critical. Use peel ply to deliver a fresh, textured surface, then solvent wipe and lightly abrade where specified. Apply film adhesive uniformly and vent edges to prevent trapped volatiles. Use controlled pressure with caul plates to maintain thickness. Validate adhesion with witness panels and maintain traceable records of every preparation step.
#8 Ply orientation and stacking sequence optimization
Performance depends on fiber direction. Plan balanced and symmetric stacks, such as 0, plus or minus 45, and 90, to control stiffness, warpage, and coupling. Tailor local plies to carry loads around cutouts, hard points, and joints. Taper ply drop offs gradually to reduce interlaminar stress and avoid delaminations. Split thick plies into multiples to lower resin pockets and improve compaction. Add interleaves where impact resistance is required, and maintain continuity through ribs and frames. Use digital lamination tools and laser projection to prevent orientation errors. Verify fiber angles with audit sheets and mark each ply during layup.
#9 Integrating features, lightning strike, and through thickness toughening
Many aerospace parts require embedded features during layup. Co cure stringers, doublers, and hard points with controlled adhesive films to maintain load paths. Integrate lightning strike mesh or expanded copper at the outer skin without trapping air, and tie mesh overlaps to structural plies for conductivity. Place sensor channels and wiring conduits with dedicated tapes so they do not print through. Where damage tolerance is critical, apply interleaf toughening or z pinning per specification, and track density and placement. Maintain smooth transitions at feature edges using caul sheets and intensifiers to ensure consistent compaction and surface quality.
#10 In process quality control and cure monitoring
High reliability requires disciplined checks during layup and cure. Use laser projection to verify ply boundaries and orientations before bagging. Barcode every ply kit and capture signoffs in the traveler to enforce configuration control. Bag with calibrated consumables, perform vacuum drop tests, and log leak rates. Place thermocouples at thick sections and corners to watch gradients, and use dielectric cure monitoring where allowed to track resin conversion. Control ramp, dwell, and cool rates to limit residual stress. After cure, confirm thickness, porosity, and bond quality using approved inspection methods, then feed results back into process capability improvement.