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 higher strain-rate loading.

In conventional resin printing, layers behave like smooth plates stacked together and bonded, but they can shear easily 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 realized shear response of the printed structure under dynamic loading.

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 strong macromechanical interlocking.

When loading becomes fast, dynamic, or highly variable, this small-scale grip is no longer sufficient 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 slippage increases, stresses accumulate rather than redistribute, making the structure more prone to sudden fracture during service.

High strain-rate fracture behavior is also influenced by the numerous pores or defects present in the resin, which further concentrate internal stresses.

Let us explain why this matters 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 transferred smoothly from one layer to the next, just like torque passing 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 causes the small “teeth” to slip, leading to rapid stress buildup and crack initiation. With strong mechanical interlocking, the layers remain engaged, resisting bending and sudden impacts without separating.

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

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

EI = E × I

Where:

E is the elastic modulus (intrinsic material stiffness).
I is the second moment of area (a geometric property describing cross-sectional distribution relative to the bending axis).

When a part repeatedly bends under cyclic or rapid loading, internal stresses accumulate and may eventually lead to fatigue failure. By increasing bending stiffness, the structure deflects less during each cycle, reducing strain accumulation between layers.

When layers remain firmly interlocked instead of slipping, crack formation is delayed, significantly improving durability under moderate dynamic and repeated loading conditions.

By introducing macrotexture in the layers, the overall geometry of the beam remains unchanged. The classical second moment of area (I) is not increased.

Instead, macro-mechanical interlocking suppresses interlayer slip and improves stress coupling across the full thickness of the structure. This allows the printed part to behave more like a unified, monolithic section under load.

In other words, the macrotexture does not change geometric stiffness parameters. It improves how effectively the structure realizes its inherent bending stiffness during dynamic and cyclic loading.

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 beam bends, different regions experience different stresses:

• The outermost surface on one side undergoes tension.
• The opposite outer surface undergoes compression.
• Between them lies the neutral axis, where bending stress transitions from tension to compression.
• Near this central region, shear stresses are highest.

In a monolithic solid beam, these stresses are smoothly distributed because the material is continuous and fully bonded.

However, in layered 3D printed resin structures, the material is built layer by layer. If interlayer bonding is limited to small-scale chemical adhesion, microscopic slip can occur under bending. This slip often initiates in regions of high shear near the neutral axis and may propagate outward with increasing load. Simultaneously, tensile stresses at the outer surface can initiate cracks that grow through the thickness.

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

The Glimmer macro-mechanical interlocking improves stress coupling across the entire thickness. It enhances resistance to shear-driven layer separation near the neutral axis while also improving tensile and compressive load transfer at the outer surfaces.

The macrotexture does not alter beam geometry or shift the neutral axis. It strengthens how effectively stresses are transmitted throughout the printed structure.

Layered resin 3D printing inherently produces structures built from sequential laminas. While chemical adhesion may be sufficient under low or quasi-static loading, structural behavior changes under real service conditions.

Common limitations include:

❌ Interlayer shear weakness under dynamic loading
❌ Crack initiation along planar layer interfaces
❌ Reduced performance under cyclic bending
❌ Stress amplification due to porosity

Conventional slow strain-rate or quasi-static testing may not fully reveal these vulnerabilities.

The Glimmer macrotextured FEP film introduces a controlled macro-mechanical interlocking pattern into every printed layer.

This architecture:

✅ Suppresses interlayer slip during bending
✅ Improves stress coupling across the full thickness
✅ Reduces the likelihood of planar delamination
✅ Enhances structural integrity under moderate dynamic strain rates
✅ Improves damage tolerance under cyclic fatigue

 ✅ By increasing effective bending stiffness, the structure undergoes lower strain for the same applied load during cyclic bending. 

Importantly, this improvement is structural. Part geometry remains unchanged, and intrinsic material modulus does not increase due to macrotexturing alone. Instead, the layered structure behaves more like a unified section during service.

When macro-mechanical interlocking is combined with NETFIL Industrial Processing (porosity reduction):

• Effective elastic modulus improves due to defect reduction.
• Stress concentration from micro and nano-porosity decreases.
• Fracture initiation becomes less defect-driven.
• Resistance to moderate high strain-rate loading improves further.

Together, these strategies address:

• Material-level integrity (porosity control)
• Structural-level coupling (interlayer mechanical engagement)

This combined approach improves damage tolerance in layered resin structures beyond what chemical bonding alone can achieve.

Glimmer Inertia FEP Film does not alter resin chemistry. It strengthens mechanical engagement between layers.

By improving interlayer locking, it enhances effective stiffness, durability, and damage tolerance to cyclic loading.

The result is resin-printed components that behave more like engineered solids than stacked laminas.

This represents a structural upgrade in how 3D printed composites perform.

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 greater. While single-unit crowns experience limited flexure, larger restorations benefit substantially from improved interlayer stiffness and resistance to deformation.

✅ See the difference yourself. Print a simple test specimen and apply rapid bending by hand. Parts produced with Glimmer macrotextured film resist sudden breakage more effectively than conventional prints, demonstrating improved structural engagement without specialized equipment.

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

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

Bending stiffness depends on both elastic modulus and structural configuration. The macrotextured architecture enhances interlayer mechanical coupling, thereby increasing effective bending stiffness without altering resin chemistry.

The observed increase in secant modulus reflects improved structural performance, not a change in intrinsic material stiffness.