A new way to think about lightweight performance

Lightweight engineering is often seen as a compromise: if you reduce weight, you lose strength. That’s true when reinforcement is limited by the manufacturing process. But when fibers can be placed exactly where they work best, the relationship changes. Weight can go down, while performance goes up.

To demonstrate this, we compared four rods with the exact same geometry: 8 mm in diameter and 300 mm in length. From the outside, they look identical. Inside, they behave very differently.

Four rods, four reinforcement strategies

The first rod is a standard PLA print. It provides a baseline: easy to make and low cost, but mechanically limited. All of its strength comes from the polymer alone.

The second rod represents the upper limit of continuous-fiber 3D printing. It is manufactured with the maximum fiber content the process allows. It is stronger than pure PLA, but still inherits the constraints of fiber-on-path printing: fibers must follow curved toolpaths, adapt to the geometry and cannot fully align with the direction of the load.

The third rod is an extruded aluminium alloy bar, also ø 8 mm. Aluminium is widely used as a lightweight structural material and serves here as a reference for stiffness-to-weight performance.

The fourth rod takes a different approach. Using CFIP, we printed a PLA outer shell and reinforced the interior with a 6 mm continuous carbon-fiber rod inserted straight through the cavity. This reinforcement is perfectly straight, fully continuous and aligned with the structural load — the ideal configuration for stiffness, strength and fatigue resistance.

Why CFIP achieves more with less

The difference in internal architecture explains the outcome. A continuous carbon-fiber core can carry bending, tensile and torsional loads far more efficiently than printed fibers restricted by geometry — and even more efficiently than a solid aluminium bar of the same size.

Because the CFIP rod concentrates reinforcement exactly where load transfer is maximised, the outer shell can remain thin. As a result, the total mass of the CFIP rod is significantly lower.

This is why the CFIP rod achieves the seemingly counterintuitive result: half the weight and twice the performance. It uses less material yet behaves like a much stronger structure. Strength is not dispersed through layers or patterns — it is placed precisely where it works.

The impact beyond this test

Although simple, this comparison has broad implications. UAV arms and frames can become lighter while increasing stiffness and flight endurance. Automotive brackets and safety-critical components can reduce mass without compromising reliability. Robotic tools can carry higher loads with less energy consumption. Any application where performance-to-weight matters benefits from placing reinforcement in the optimal position rather than following the constraints of the print path.

Four rods. Same size. Same shape. Completely different outcomes.

HALF THE WEIGHT. TWICE THE PERFORMANCE. That’s what happens when you reinforce from the inside — not from the toolpath.