Fiberon PET-GF15 – engineering PET 3D printer filament - 15% glass fibers

Fiberon PET-GF15 – engineering PET 3D filament with 15% glass fibers

Fiberon PET-GF15 is a high-performance composite filament for FFF/FDM 3D printers, based on PET (polyethylene terephthalate), reinforced with about 15% glass fibers. The material is designed to combine the convenience of "everyday" filaments with the mechanical properties of industrial engineering plastics – high stiffness, long-term stability, and excellent resistance to temperature and chemicals.

Thanks to the special formula of PET + glass fibers, Fiberon PET-GF15 achieves bending strength of about 104 MPa, Young's modulus in XY over 4 GPa, and Heat Deflection Temperature (HDT) up to 133.7 °C at 0.45 MPa after annealing. This allows for reliable operation of parts subjected to mechanical and thermal loads – for example, in automotive, industrial, and engineering applications.

The filament is available in a 1 kg spool, diameter 1.75 mm and is part of the Fiberon series from Polymaker, which is aimed at professional users and advanced enthusiasts. The packaging is made of recyclable cardboard – a practical solution for manufacturing environments where a lower environmental footprint is also sought.

Fiberon PET-GF15 is a logical choice if you are looking for a material for functional prototypes, assembly fixtures, enclosures, and end parts that need to withstand vibrations, higher temperatures, and long-term use. At the same time, it remains relatively easy to work with compared to many other engineering filaments.

Technology and material quality

The core of Fiberon PET-GF15 is the well-known PET, supplemented with 15% short glass fibers. These fibers significantly increase the stiffness and dimensional stability of the parts while limiting shrinkage and deformation during cooling. As a result, the material behaves predictably and allows for tighter tolerances compared to standard PETG or PLA.

According to the technical data sheet, the density of the material is about 1.43 g/cm³ at 23 °C. Mechanical tests on 3D printed samples show:
– Young's modulus XY: ~4.14 GPa;
– Tensile strength XY: ~59.9 MPa;
– Tensile strength Z: ~48.2 MPa;
– Bending strength XY: ~104.2 MPa;
– U-notch Charpy impact strength XY: ~8.7 kJ/m².

Especially important with this material is good layer adhesion. In the Z-direction, Fiberon PET-GF15 reaches about 80 MPa flexural strength, which is significantly better behavior compared to many classic fiber composites, where the Z-layer remains the weak point.

In terms of moisture absorption, PET-GF15 is far more stable than nylon filaments. The equilibrium water absorption at 70% relative humidity and 23 °C is about 0,32%, which means less dimensional changes and more predictable behavior during long runs.

Performance and workflow

Fiberon PET-GF15 is designed to operate at relatively high temperatures, but with good control over the process. The recommended settings are:

• Nozzle temperature: 280–310 °C;
• Bed temperature: 70–80 °C;
• Chamber temperature: ambient/room;
• Fan: off (0%);
• 3D printing speed: from ~30 to 250 mm/s depending on the printer and geometry.

Thanks to the stable PET matrix and selected glass fiber fraction, the material allows for high speeds, including on more modern CoreXY and AMS systems, without significant degradation of layer quality. For better layer adhesion and strength, it is advisable to work slower in critical areas (overhangs, thin ribs, precise holes).

The manufacturer recommends pre-drying at 100 °C for about 10 hours when the filament has been outside a dry box or when "bubbling" and micropores are observed in the layer. For maximum thermal resistance and stability after printing, annealing at 120 °C for 16 hours can be applied, which raises the HDT to the specified 133.7 °C at 0.45 MPa.

It is recommended to use adhesive for high-temperature materials or a textured PEI surface. PET-GF15 adheres very strongly to such beds; Polymaker explicitly advises that the part should be removed after complete cooling or with the help of a release agent to avoid surface damage.

For more detailed settings and profiles, you can use the ready-made configurations that Polymaker provides through its profile library.

Compatibility, ecosystem, and spool design

Fiberon PET-GF15 is compatible with most FFF/FDM 3D printers with 1.75 mm filament, provided they have:

• all-metal hotend, reaching at least 280 °C;
• hardened steel or ruby nozzle – glass fibers significantly wear out brass nozzles, and according to TDS, their lifespan can drop to about 9 hours of 3D printing;
• well-managed bed heating and, if possible, a closed volume for larger details.

The material has been tested by Polymaker for use with AMS and other multi-material systems, as the fiber length and its improved "flexibility" compared to many CF filaments allow for stable feeding even through longer PTFE paths.

The spool is made of cardboard with precise holes for guiding and securing the filament, which facilitates use in dryers and filament cabinets. The net amount of material is 1 kg, and the additional QR code on the label leads to TDS and profiles for 3D printing – convenient for quick checking of settings directly from the workplace.

Fiberon PET-GF15 works excellently with popular slicers like PrusaSlicer, Bambu Studio, OrcaSlicer, and Cura – standard formats such as STL, 3MF, and OBJ are used. For maximum compatibility and repeatability, it is good practice to base your settings on the official profiles and then fine-tune them according to the specific printer.

Professional use scenarios

Thanks to the combination of hardness, heat resistance, and low moisture absorption, Fiberon PET-GF15 is suitable for a wide range of engineering applications:

• Automotive clips and housings in the engine compartment – after heating, the parts withstand temperatures above 120 °C and are resistant to oils and many technical fluids. Suitable for cable holders, connectors, mounting brackets, and covers.
• Industrial parts exposed to constant stress – gear covers, sensor holders, mounting blocks, and automation elements, where low deformation and stable dimensions are critical.
• Jigs and fixtures – mounting, calibration, and inspection devices that must remain geometrically stable under load and with repeated use.
• Enclosures and boxes for electronics – the PET base provides good chemical resistance and a higher working temperature compared to standard PLA, and the surface has a pleasant matte finish that hides the layers.
• Functional prototypes and small series of end products – consoles, handles, quick adapters, elements for drones and robots, where the balance between weight, strength, and easy reprinting in 3D is valued.

After annealing, the dimensional change is below 0.5 %, allowing for the design of parts with precise fits, e.g. hinge joints, sliding guides, and components that attract to metal elements.

Limitations and best practices

Although PET-GF15 is relatively easy to print composite filament, there are several important features:

• Nozzle wear: glass fibers are highly abrasive. The manufacturer recommends mandatory use of hardened or ruby nozzles; with a brass nozzle, the lifespan may be only a few hours of printing.
• Temperature requirements: if your printer only reaches 280–285 °C, the material can be printed, but it is advisable to reduce the speed and monitor layer adhesion, especially for thick parts.
• Moisture: the material should be stored in a dry environment (below 20% RH) and preferably in a filament dryer. In case of "cracking" and white spots in the layer – dry the filament according to TDS.
• Annealing: perform it on a flat surface, preferably together with the base and with supports preserved for parts with bridges and overhangs to avoid warping. Expect slight color lightening – this is not a defect, but a result of a change in the material's crystallinity.
• Bed adhesion: PET-GF15 adheres strongly to a clean textured PEI surface. Allow the bed to cool completely or use a thin layer of adhesive/release agent to protect the coating.

It is recommended to create a calibration model to confirm dimensions before serial printing, especially if you plan subsequent annealing.

Technical specifications and sources

Technical specifications

Links to tables and charts for download

• Fiberon Material Comparison Guide – comparison tables and charts with other Fiberon filaments: https://fiberon.polymaker.com/material-comparison/