NETFIL's Glimmer Inertia FEP Film introduces a macrotextured surface that becomes imprinted into every printed layer. This geometric imprinting transforms interlayer bonding from purely chemical adhesion into mechanical interlocking, significantly improving damage tolerance under high strain rate loading.

In conventional resin printing, layers behave like smooth plates stacked together and bonded, but they are easy to shear under rapid force. Under sudden loading, stress localizes and cracks propagate quickly due to weak interlayer shear transfer.

Our NETFIL Glimmer FEP macrotexture changes this behavior. The imprinted surface acts like intermeshing gear teeth between layers, creating macromechanical keys that resist material slip. This enhances interlayer shear resistance and effectively increases the shear modulus (G) of the printed structure.

To understand why, let us break it down step by step.

In conventional resin 3D printing, layers are held together mainly by chemical bonding. At low or steady rates of loading, this bond provides sufficient grip between layers. However, chemical bonds exist at a very small scale and do not create a strong macromechanical interlock.

When the loading becomes fast, dynamic, or highly variable, this small-scale grip is no longer enough to keep the layers firmly engaged. Instead of transferring stresses smoothly from one layer to the next, material slippage can occur at the interfaces. As this slippage increases, stresses begin to accumulate rather than redistribute, making the structure more prone to sudden fracture during service.

This high strain rate–related fracture failure is also influenced by the innumerable pores or defects present in the resin, which cause stresses within the material to accumulate further.

Let us explain why this is important using an analogy.

• The layers act like large, fully engaged gears instead of tiny gears that can slip.
When the “teeth” between layers are strong and well interlocked, force or stress is smoothly transferred from one layer to the next, just like torque passing cleanly through properly meshed gears. The part behaves like one solid unit, not like stacked sheets that can shift under stress.

• When force increases suddenly, the gears stay locked instead of slipping.
In a weakly bonded structure, fast loading makes the tiny teeth slip, causing stresses to build rapidly and cracks to form. With strong mechanical interlocking, the gears remain engaged, resisting bending and sudden impacts without breaking apart.

So what does this improved interlocking actually change in the real structure? It changes how the part resists bending.

Bending stiffness (EI) determines how resistant a part is to bending forces. It is given by:

EI = E × I

Where:

E is the elastic modulus, representing the stiffness of the material itself.
I is the second moment of area, which describes how the material is distributed relative to the bending axis.

When a part repeatedly bends under cyclic or rapid loading, internal stresses build up and eventually lead to fatigue failure. By increasing bending stiffness, the structure flexes less during each cycle, reducing stress accumulation between layers. When the layers remain firmly interlocked instead of slipping, crack formation is delayed, significantly improving long-term durability under high strain rate and repeated loading conditions.

When a beam bends, the outermost layers experience the highest stress. The farther material is placed from the center of bending, the more it contributes to stiffness.

Think of it like gears again.

If the gear teeth are shallow and close to the center, they do not generate much leverage. If the teeth are larger and extend farther outward, they engage with greater mechanical advantage. The farther the contact is from the center, the stronger the resistance to motion and the greater the mechanical advantage.

The second moment of inertia (I) works the same way. Material positioned farther from the neutral bending axis contributes disproportionately more to bending stiffness. Even small outward geometric changes can significantly increase resistance to bending.

By introducing macrotexture in the layers, structural material is effectively positioned farther from the neutral axis. This increases I, which increases EI, making the part stiffer and more resistant to rapid loading and fatigue-related damage.

For eliminating material porosity that decreases elastic modulus (E), we offer our proprietary degassing solution known as NETFIL Industrial Processing for all 3D printed composite resins, including chairside resin composites.

• When a part bends, the top layers are stretched and the bottom layers are compressed.
The center line between them is called the neutral axis, where bending stress is minimal but internal sliding forces (shear) are strongest.

• Material farther from the center resists bending more strongly.
Just like larger gears with wider engagement provide greater leverage, material positioned farther from the bending center increases stiffness significantly.

• Bending is not the only force at work. Layers also try to slide over each other.
Shear forces are highest near the middle of the structure. If the layers are weakly bonded, this is where internal slipping begins.

• That is why macrotexture must run through all printed layers, not just surface regions.

Outer layers improve bending resistance, while internal interlocking prevents layer sliding. Together, they make the entire structure behave like one solid, fully engaged gear system.

Traditional Issues with Resin Prints:

❌ Low shear strength between layers, leading to weak bending stiffness.
❌ Breakage along layer lines due to poor stress transfer at high strain rates.
❌ Limited mechanical performance for demanding engineering applications.

How Glimmer FEP Film Fixes This:

✅ Macrotexturing locks layers together, dramatically improving shear modulus (G) under high strain rate loading.
✅ Enhanced moment of inertia (I) makes parts much stiffer and more resistant to bending.
✅ Better stress distribution results in stronger, more durable, and more damage-tolerant parts.
✅ No change to resin chemistry, making it easy to adopt in medicine and dentistry where biocompatibility matters.

Glimmer Inertia FEP Film does not alter resin chemistry. It strengthens how layers engage mechanically. By improving interlayer locking, it enhances stiffness, durability, and resistance to rapid or cyclic loading.

The result is resin printed components that behave more like engineered solids than stacked layers, expanding their use into demanding applications such as engineering, aerospace, dental, and biomedical fields.

This is not a small improvement. It represents a structural upgrade in how 3D printed composites behave.

 The structural advantage becomes even more significant in long-span restorations such as splints, full-arch bridges, and All-on-X prostheses, where bending and deflection are inherently higher. While single-unit crowns are well supported and experience limited flexure, larger prostheses benefit substantially from improved interlayer stiffness and resistance to deformation. 

✅ See the difference for yourself. Print a simple test specimen and apply quick bending or impact by hand. The improvement is immediately noticeable. Parts produced with Glimmer macrotextured film resist sudden breakage far better than conventional prints, making the performance difference clear without specialized equipment.

Mechanical testing of parts printed using our macrotextured FEP film demonstrated an increase in secant modulus during bending evaluation. This indicates improved effective bending stiffness of the laminated structure.

This increase should not be confused with an increase in flexural modulus. Flexural modulus is an intrinsic property of the material and remains unchanged.

Bending stiffness depends on both the elastic modulus and the structural configuration of the printed part. The macrotextured architecture enhances mechanical interlocking between layers, thereby increasing effective bending stiffness without altering resin chemistry.

The observed increase in secant modulus reflects improved structural performance rather than a change in intrinsic material stiffness.