A light-aircraft maintenance workshop needed to repair the fiberglass shell of a glider and produce a small number of internal bracket-type parts. The parts were not large but had complex shapes. The resin had to wet the glass fabric well, provide enough working time for lay-up and edge sealing, and avoid excessive exotherm inside the mold.
According to the referenced TDS, the system offers:
- Resin viscosity 1000–1500 mPa·s at 25 °C; mixed viscosity 500–700 mPa·s at 25 °C.
- Pot life approximately 110–160 min at 25 °C for a 100 mL batch (TECAM, 65% RH).
- Suitability for wet lay-up, RTM, pressure moulding and filament winding.
- Post-cure capability, with a maximum attainable glass transition temperature in the range of 130 °C.
1. Process Approach
The repair area was sanded, dedusted, and degreased. A 280–300 g/m² plain-weave E-glass fabric was used. The mix ratio was LY 5052 : Aradur 5052 = 100 : 38 by weight. Manual mixing took 3–5 min, including scraping the vessel walls and bottom. Repairs were made by wet lay-up; small brackets were produced using a simple silicone mold and RTM infusion.
Lay-up was completed at 23–25 °C. For thin layers of 0.4–0.7 mm, gelation started at 5–6.5 h and ended at 7–8 h, which allowed staged work. After initial cure, the parts were kept 7 days at room temperature, then post-cured 1 day at 23 °C + 8 h at 80 °C, giving a Tg onset of 112–116 °C. This met the service requirements of non-primary glider components.
2. Results and Properties
For a 16-layer E-glass 1:1 fabric laminate with 45–46% fiber volume content, cured 10 h at 80 °C, the TDS reports the following typical values:
| Property |
Condition / Standard |
Typical value |
| Flexural strength |
ISO 178, 10 h @ 80 °C |
440–490 MPa |
| Flexural modulus |
ISO 178, 10 h @ 80 °C |
20000–22000 MPa |
| Tensile strength |
ISO 527, 10 h @ 80 °C |
360–390 MPa |
| Interlaminar shear strength |
Wet lay-up, 10 h @ 80 °C |
approx. 60–65 MPa |
| Flexural strength after water immersion |
30 days in H₂O at 23 °C |
380–400 MPa |
In this case, the repaired panel cured under similar conditions showed a dense surface, no blushing, and good adhesion to the existing shell. After 30 days immersion in water at 23 °C, flexural strength dropped from 440–490 MPa to 380–400 MPa, which is consistent with the well-known behaviour that fiberglass composites lose some properties after water absorption but remain serviceable.
3. Why This System Was Chosen
- Low viscosity: suitable for hand lay-up and RTM.
- Long pot life: good for repair, training, and low-volume production.
- Room-temperature cure: no large autoclave required.
- Post-cure improves thermal performance: suitable for lightweight aerospace structures.
- The TDS notes the system’s background in German aircraft authority-qualified glider production, making it appropriate for non-primary aerospace composite applications.
4. Summary
Araldite LY 5052 / Aradur 5052 is not the fastest-curing epoxy, but it is highly practical for glider repair, prototyping, and low-volume fiberglass parts: easy to handle, good wet-out, controllable exotherm, and sufficient thermal performance after post-cure. For auxiliary aerospace structures that do not require 180 °C-class high-temperature curing, it is a sound engineering choice.
Note: All numerical data above are typical values taken from the referenced TDS; actual results depend on part geometry, laminate thickness, fibre content and process control. This case is a representative engineering illustration, not a project-specific test report.
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