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Automotive composite lattice rebar is moving from lab demo to line-ready reality — and it has clear implications for EV design, cost, and manufacturing. In a recent Munro conversation with WEAV3D’s leadership, the team walked through how lightweight lattice tapes embedded in thermoplastic parts can replace ribs, reduce scrap, and tune stiffness where you need it most.
Think of it as “rebar for plastics” engineered for high-rate production — a modular reinforcement that elevates everyday polymers into structural performers.
From Soft Felt to Steel-Like Stiffness
Start with a familiar interior substrate: recycled non-woven “shoddy.” On its own, a compression-molded sheet feels flimsy. Add a light glass-fiber lattice and stiffness jumps; switch to carbon-fiber tape and the panel approaches the stiffness of 20-gauge stainless steel — at a fraction of the mass. The magic lies in placing continuous fibers only where the load path runs. Short fibers in injection molding lose length through attrition; continuous tapes carry load end-to-end, cutting reliance on the polymer matrix for transfer. Engineers can now orient reinforcement along principal stresses — not wherever the gate and flow knit lines decide.
Killing the “Ribs + Back-Injection” Tax
Instrument panel toppers show the value immediately. Today, many IP skins require back-injected ribs to hit NVH and stiffness targets. That means two big tools, two processes, and added weight. With lattice reinforcement embedded during thermoplastic compression molding, teams can drop rib density or skip the back-injection step altogether. You keep attachment features where needed, but you stop paying the “same-size tool twice” penalty. This is lean design in action — fewer steps, less tooling, smaller BOMs.
Homogeneous vs. Tailored Lattices
WEAV3D demonstrated both uniform and non-uniform lattice patterns. A homogeneous grid lifts stiffness universally. A tailored grid does more — it shifts density and orientation to where the part sees load. Volkswagen’s cellulose non-woven example illustrated a denser mesh in critical spans and a lighter mesh elsewhere. The outcome is a meta-material panel: different stiffness in different zones, tuned at the tape level. For engineers, this means you can shape the stress-strain curve locally without adding exotic layups or extra processing steps.
Sandwich the Strength, Keep the Toughness
A door inner developed with Clemson and Honda highlights another advantage. The team used a polypropylene core with carbon-fiber lattices on both faces. Under side-pole loading, the tensile face cracked at the fiber layer while the PP core stayed intact — so the panel rebounded after unloading. Instead of the brittle cliff of a conventional composite, the hybrid panel delivered a high-stiffness “straight line,” then a controlled cracking plateau with useful residual load. That combination — stiffness plus toughness — is exactly what crash engineers want.
Cost, Scrap, and Purchasing Reality
Carbon fiber scares purchasing because price is often quoted per pound. That framing hides a key fact: carbon’s density is ~0.8–0.9 g/cc versus glass at ~2.7 g/cc. On a per-volume basis, you need far less carbon to fill the same space, and continuous tapes target only the load-bearing paths. In the door case, lattice-reinforced PP came in at roughly half the cost of a carbon organosheet and cut trim scrap by 63% by removing expensive fiber from areas destined for the trim die. Another trial hit a 23% mass reduction over an all-carbon solution — with only ~7% of the part’s mass in carbon, thanks to selective placement. When you price by part, not by pound, the business case gets compelling.
Simulation-Driven Placement
Design freedom means little without predictive tools. The WEAV3D process pairs with Altair HyperWorks-class solvers to simulate fiber orientation, density, and resulting stiffness/strength across the lattice. Teams can decide whether the fiber or the polymer should fail first, then drive tape width, spacing, and orientation accordingly. Outputs guide mold-ready lattice layouts that reflect forming realities — including regions you’ll trim out. This simulation-to-press loop shortens iteration cycles and supports early cost visibility.
Manufacturing Fit: High-Rate and Recyclable
Because the tapes are thermoplastic, you can integrate them into high-rate compression molding or co-molding flows without autoclaves or long cure cycles. Trim scrap remains thermoplastic, so plants can upcycle it into other injection-molded components. The process supports mixed materials — glass for isotropic toughness, carbon for directional stiffness, and even embedded conductors. One concept routes aluminum foil on a glass tape “carrier,” shielded above and below by glass. Mill a small land to expose the conductor; you’ve added a robust circuit without fishing a harness through a tortuous geometry.
System-Level Value: Delete Brackets, Shrink Beams
Once plastic panels get truly stiff, they can carry load. That opens a path to delete secondary brackets under the cross-car beam, or even downsize the beam if the IP carrier shoulders more work. The lesson: do not bolt a new structural panel on top of legacy structure and claim “no savings.” Redesign the system. Let the stiffened panel span the gap. Validate with simulation, then prove in rig and vehicle. Munro’s teardown mindset — remove parts, reduce interfaces, sharpen manufacturability — applies directly here.
Practical Guidelines for Engineers
- Start with a load map. Identify spans, screw bosses, and clip zones. Use lattice density and orientation to replace ribs in those paths.
- Think in sandwich. Face lattices with a ductile thermoplastic core to pair stiffness with crash-friendly toughness.
- Price by part. Quote per-part economics that include tool count, cycle time, and scrap — not just $/lb.
- Design for trimming. Pull tape out of obviously trimmed regions to avoid paying for scrap.
- Prototype failure modes. Decide whether fibers or matrix should crack first; tune spacing and tape modulus to hit that target.
- Plan recycling. Keep families of thermoplastics compatible to upcycle trim efficiently.
- Coordinate with attachments. Use local lattice “pads” under fasteners; eliminate unneeded back-injected ribs.
- Measure what matters. Compare deflection at load, modal frequencies, and post-impact residual strength — not just coupon tensile.
Where It Fits First
Expect early wins in IP toppers, door modules, load floors, and trim panels that currently “need ribs.” EVs magnify the value: every kilogram saved extends range or enables smaller packs. Interiors dominate part count; shaving tools and steps pays back fast at scale. Suppliers who adopt lattice reinforcement can turn commodity plastics into engineered structures — a differentiator in a crowded RFQ field.
The Bigger Picture
Lattice-reinforced thermoplastics align with the industry’s shift to modular, recyclable materials. They also reflect a broader Munro theme: seek function in the fewest parts. Replace thickness and rib forests with targeted reinforcement. Trade assemblies for tuned meta-materials. When teams take that mindset into design reviews, they reduce weight, cost, and complexity while improving performance.
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