FAILURE ANALYSIS REPORT

REF: FAR-2026-0872
Date: September 3, 2026
Client: Confidential (European Wind Farm Operator)
Analyzed By: Guangzhou Composite Testing Laboratory (GCTL)

1. Executive Summary

Three 3.2MW wind turbine blades from the same production batch were installed on a single turbine in December 2024. In June 2026, the turbine experienced a blade failure. Blade A suffered complete structural failure at the mid-span and separated from the hub. Blade B was found to have delamination on the trailing edge. Blade C was intact.

Blades A and B were recovered and submitted to GCTL for failure analysis. Blade C remained on the turbine and was not available for testing.

This report documents the findings of the laboratory analysis.

2. Blade Specifications

3. Visual Inspection Findings

Blade A was recovered in multiple segments. The fracture surface was examined and photographed. The fracture was located at approximately 34 meters from the root. The fracture surface was consistent with fatigue initiation followed by overstress fracture.

Blade B was recovered intact. Visual inspection revealed a 2.3-meter-long delamination on the trailing edge. The delamination was located between the outer and second glass fabric layers. No impact damage was visible. No lightning strike marks were visible.

Blade C was visually inspected on the turbine. No visible damage was reported.

Photograph Reference: FAR-2026-0872-IMG-001 through IMG-012 (see Appendix A)

4. Non-Destructive Testing (NDT) Results

Both blades were scanned using ultrasonic pulse-echo (UPE) and phased-array ultrasonic testing (PAUT).

Blade A (fractured):

• Extensive delamination was detected in the region adjacent to the fracture surface

• Delamination was concentrated in the glass fiber layers, not the carbon fiber spar

• Delamination area: approximately 3.8 square meters

• No manufacturing inclusions or foreign objects were detected

Blade B (delaminated):

• Delamination was confirmed to the trailing edge, extending approximately 2.3 meters from the 32-meter station to the 34.3-meter station

• Delamination was confined to the glass fiber layers

• No manufacturing inclusions or foreign objects were detected

Interpretation: The delamination pattern is consistent with a manufacturing defect, not operational damage. The absence of impact marks or lightning strike evidence supports this interpretation.

5. Laboratory Testing Results

5.1 Differential Scanning Calorimetry (DSC)

Cured resin samples were taken from all three blades (A, B, and C). The glass transition temperature (Tg) was measured.

Interpretation: Blades A and B had resin systems that were under-cured. The average Tg of the failed blades was approximately 7°C below the minimum specification. Blade C was within specification.

5.2 Fiber Volume Fraction (FVF)

Samples were cross-sectioned and examined under optical microscopy. The fiber volume fraction was measured.

Interpretation: Blades A and B had lower fiber volume fractions than Blade C. The lower FVF is consistent with incomplete resin infusion or insufficient vacuum pressure during the VARI process.

5.3 Interlaminar Shear Strength (ILSS)

ILSS testing was performed on samples from all three blades using a standard short-beam shear test.

Interpretation: The ILSS values for Blades A and B were significantly below specification. The lower ILSS is consistent with the lower Tg and lower FVF. The combination of under-cured resin and reduced fiber content resulted in reduced interlaminar strength.

6. Root Cause Analysis

The failure is attributed to a manufacturing defect in Blades A and B.

Primary Root Cause: Under-cured resin system. The resin in Blades A and B did not reach the required glass transition temperature. This is consistent with:

• Inadequate cure temperature in the autoclave or oven

• Insufficient cure time

• Incorrect resin-to-hardener ratio (unverified due to lack of batch records)

Secondary Root Cause: Low fiber volume fraction. The resin infusion process did not achieve the specified fiber volume fraction. This may be due to:

• Insufficient vacuum pressure

• Inadequate resin flow

• Fiber architecture variation

Contributing Factor: Batch record documentation was incomplete. The manufacturer was unable to provide full process records for the batch in question. It is not known if the resin batch was correctly mixed, if the cure cycle was correctly applied, or if the vacuum pressure was within specification.

7. Corrective Action Recommendations

Based on the findings of this analysis, the following corrective actions are recommended:

For the Manufacturer:

1. Validate the cure cycle for all future production. Provide proof of cure temperature and time via thermocouple data.

2. Validate resin-to-hardener mixing ratios for each batch. Provide batch-specific mixing records.

3. Validate vacuum pressure during infusion for each blade. Provide pressure logs.

4. Conduct DSC testing on each production batch. Maintain records for review.

For the Buyer:

1. Require batch-specific process documentation before accepting shipment.

2. Require independent third-party testing of one blade per production batch for Tg, FVF, and ILSS.

3. Consider adding a mandatory NDT inspection (UPE/PAUT) of the full blade length before installation.

8. Conclusion

Blades A and B failed because the resin system was under-cured and the fiber volume fraction was below specification. These manufacturing defects reduced the interlaminar shear strength of the composite, leading to delamination and ultimately structural failure.

The manufacturer's process control was inadequate. Batch-specific documentation was not maintained, making it impossible to identify the specific cause within the manufacturing process.

The buyer is advised to implement additional quality controls and documentation requirements for future blade purchases.

9. Appendices

• Appendix A: Photographs of Blade A fracture surface (12 images)

• Appendix B: Photographs of Blade B delamination (8 images)

• Appendix C: DSC thermograms for Blades A, B, and C

• Appendix D: Optical microscopy images for FVF measurement (15 images)

• Appendix E: ILSS test data and stress-strain curves

• Appendix F: NDT ultrasonic scanning images (22 images)

Report Prepared By:
Dr. Li Wei, Senior Materials Engineer
Guangzhou Composite Testing Laboratory (GCTL)
September 3, 2026

Reviewed By:
Dr. Chen Ming, Laboratory Director
Guangzhou Composite Testing Laboratory (GCTL)
September 4, 2026

Three blades from the same production batch. Two failed. One survived. Lab analysis identified the root cause. Here is t

Three blades from the same batch. Two delaminated. One survived. Lab analysis identified the root cause. Here is the full failure report.

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