Prepreg vs Dry-Fabric Lamination

A body-armor panel is many layers of ballistic fabric bonded together with resin into a single composite. OEMs build these panels using one of two methods: prepreg-based construction or dry-fabric lamination. The choice has real implications for cost, weight, manufacturing yield, and the specific suppliers an OEM relies on.

Prepreg construction

Prepreg = "pre-impregnated." The ballistic fabric arrives from the supplier already coated with uncured thermoplastic resin at a precise resin-to-fiber ratio. The OEM cuts the prepreg to panel shape, stacks layers in the designed sequence, and heat-presses the stack to cure the resin into a rigid laminate.

Suppliers: Barrday, JPS Composite Materials, Hexcel.

Pros:

Resin ratio is pre-controlled — consistent panel performance
Simpler OEM manufacturing step (stack + press, no resin application)
Higher first-pass yield; less scrap from resin-application defects
Supplier does the expensive part; OEM focuses on integration

Cons:

Higher material cost per unit (prepreg is expensive)
Storage requirements — some prepreg types require refrigerated storage before use
Less OEM control over the resin chemistry

Dry-fabric lamination

Dry-fabric construction uses bare ballistic fabric (Kevlar, Twaron, Dyneema, Spectra) from the fiber producer. The OEM stacks layers, applies resin at manufacture time (spray, roll, or dip-coat), and heat-presses.

Suppliers: fiber producers directly (DuPont, Teijin, Avient, Honeywell) plus a separate resin supplier.

Pros:

Lower material cost per unit
OEM controls resin chemistry — can tune for specific ballistic goals
No cold-chain storage requirement
Wider supplier options

Cons:

OEM process complexity is higher
Resin-ratio variance is a yield risk — inconsistent panels
More OEM-side equipment required (resin application, cure ovens)

Which method, which product

Most US body-armor OEMs use both methods depending on the specific product line:

Soft armor panels (Level II, IIIA) — often prepreg-based, especially premium lines. Consistency is critical for soft-armor BFS compliance.
Hard armor plate backers — dry-fabric is common, with the ceramic strike face and fiber backing bonded by a resin step at OEM manufacture.
Helmet shells — typically prepreg (aramid-based), because the shell geometry requires precise layup and curing.
Shield panels — split; prepreg for premium shields, dry-fabric for cost-focused.

The supplier-integration axis

OEMs running prepreg construction have a shorter, more controlled supply chain:

Fiber producer → prepreg supplier → OEM
3 entities

OEMs running dry-fabric lamination have a longer but more flexible supply chain:

Fiber producer → OEM (fabric side)
Resin supplier → OEM (resin side)
OEM integrates and laminates
3+ entities, more coordination

For Berry Amendment purposes (see Berry Amendment + body armor), dry-fabric construction is sometimes the only way to guarantee domestic sourcing through the whole chain — prepreg suppliers may use non-Berry-compliant fiber.

Recent trends

UHMWPE unidirectional construction (Dyneema Composite Fabric, Spectra Shield) is fundamentally a prepreg-like product — the fiber arrives as a pre-layered sheet. This blurs the line between the two methods.
Thin-laminate advances — modern prepreg technology has reduced panel thickness 10-15% at equivalent rating over the past decade.
Robotic lay-up — some OEMs are automating prepreg stacking with robotic placement. Drives consistency and labor-cost reduction.