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Fiberglass pipe breakage

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Summary

Fiberglass pipe breakage

The object

The purpose of the investigation is to characterize the material and determine the cause of the damage that occurred on the fiberglass pipe.
Investigations were conducted on two predefined areas: one area showing obvious signs of damage and the second area, on the other hand, perfectly intact.
The pipe consists of three parts: inner part, structural wall, outer wall. The following photo shows the cross section of the pipeline.

The analyses

FT-IR Analysis

Performed upon receipt of the sample; the spectrum of analysis showed a phthalic thermoset resin composition.

TGA analysis

TGA analysis was performed on the received material, both on the damaged area and the intact area.

DSC analysis

From the DSC analysis conducted on the two areas under investigation, it was seen that the thermal behavior of both areas is the same. In both areas investigated (damaged and intact), there are no signs of lack of cross-linking in the resin used.

Filler Analysis

Part of the two areas under investigation, was subjected to calcination in a muffle furnace at 700°C for about 60 minutes. The ash content obtained can be seen in the images below.

In addition, the ash was subsequently subjected to further qualitative analysis by SEM/EDS microanalysis. The composition was found to be based on oxygen (O), aluminum (Al), silicon (Si) and calcium (Ca).

The photos below show the fiberglass examined in the two areas with SEM (scanning electron microscope). Fiber diameters were measured for both areas.

The residues found on the surface were analyzed with an electron microscope (see spectrum below). The following composition was found: oxygen (O), aluminum (Al), silicon (Si), magnesium (Mg) and traces of calcium (Ca), sodium (Na) and chloride (Cl). From this finding, the surface residues consisted of fiberglass remnants and traces of salt from seawater (where the survey object was found to be immersed).

Fig. 1 – Undamaged area
Fig. 2 -Damaged area
Fig. 3 -Transverse section of the pipeline.
Fig. 4 -FT-IR Spectrum.
Fig. 5 -Ash content: undamaged area -Ash content: damaged area
Fig. 5 -Ash content: undamaged area -Ash content: damaged area
Fig. 6 – EDS spectra: Undamaged area – EDS spectra: Damaged area
Fig. 7 – SEM: undamaged area – SEM: Damaged area.

Cause of breakage

The photos below, are relevant as to the damage condition of the examined object. The first damage found on the surface is mainly characterized by significant detachment of the surface layer (see photo #1).
Observation made on the damaged surface shows the presence of craters of different sizes, which suggests the presence of bubbles (see photo No. 2).
Regarding the cross section of the damaged area in question, significant voids in the material are evident.
These defects are not present in the cross-section belonging to the intact area (see photo no.3).
In addition, the inorganic residue obtained by calcination consists of layers of glass fiber (arranged both in an orderly and random manner).
The cross section of the damaged area shows obvious defects in material integrity; these defects are not present in the cross section of the undamaged area (see photo #4).

Fig. 8 – EDS Spectrum
Fig.9 – Damage conditions

Conclusions

As a result of the chemical analysis carried out on the two investigated areas (damaged and intact), no significant differences were found, but with regard to the structural investigation of both investigated areas, significant differences were found. The damaged area is characterized by voids in the material, due to a lack of compactness of the structural layer.

This lack of structural compactness of the wall is most likely due to a lack of resin, as confirmed by the finding on the damaged area of higher glass fiber content.

In addition, the rounded shape of the defects found on the cross section suggests that the voids originated from gas development.

The development of gas is confirmed by the defects found on the surface of the damaged areas (the defects are attributable to gas bubbles).

In a fiberglass object, the degenerative phenomenon known as “osmosis” is characteristic. Osmosis is a physicochemical phenomenon consisting of the passage of a solvent, in our case water, through a membrane separating two liquids with a different salt concentration. In fact, the fiberglass pipe immersed in water constitutes the first condition for giving rise to osmosis. The second condition is that inside the fiberglass laminate there are trapped air bubbles positioned more or less in contact with the surface layer (outer part).

As first, water passes through the outer layer to go to fill the bubbles found in the structural wall. Next, the water inside the bubbles begins to dissolve anything that may be soluble.

Then this concentrated solution draws water from outside through the gel layer, after which the pressure inside the bubbles grows to form an air chamber.

The phenomenon of osmosis is a degenerative process.

Causes may be:

  • Low quality of the surface layer, e.g., a resin that is poorly impermeable to water.
  • Inaccurate processing due to the presence of air bubbles in the layers.
  • Excess catalyst used during layering.
  • Stratification performed in too cold or too humid environment.
  • Presence of impurities or solubles in the glass or resin.

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