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. 2019 Dec 26;12(1):40.
doi: 10.3390/polym12010040.

Pinned Hybrid Glass-Flax Composite Laminates Aged in Salt-Fog Environment: Mechanical Durability

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Free PMC article

Pinned Hybrid Glass-Flax Composite Laminates Aged in Salt-Fog Environment: Mechanical Durability

Luigi Calabrese et al. Polymers (Basel). .
Free PMC article

Abstract

The aim of the present paper is to study the mechanical performance evolution of pinned hybrid glass-flax composite laminates under environment aging conditions. Hybrid glass-flax fibers/epoxy pinned laminates were exposed to salt-spray fog environmental conditions up to 60 days. With the purpose of assessing the relationship between mechanical performances and failure mechanisms at increasing aging time, single lap joints at varying joint geometry (i.e., hole diameter D and hole distance E from free edge) were characterized after 0 days (i.e., unaged samples), 30 days, and 60 days of salt-fog exposition. Based on this approach, the property-structure relationship of the composite laminates was assessed on these critical environmental conditions. In particular, a reduction of failure strength for long-aging-time-aged samples was observed in the range 20-30% compared to unaged one. Due to the natural fiber degradation in a salt-fog environment, premature catastrophic fractures mode due to shear-out and net-tension were found, related to reduced joint fracture strength. This behavior identifies that this type of joint requires a careful design in order to guarantee an effective mechanical stability of the composite hybrid joint under long-term operating conditions in an aggressive environment.

Keywords: bearing; failure modes; glass-flax hybrid coposites; pinned joints; salt fog aging.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Sample geometry and (b) bearing test setup.
Figure 2
Figure 2
Stress-displacement curves at increasing aging time for pin-loaded laminates (D = 4 mm; E = 12 mm; W = 15 mm).
Figure 3
Figure 3
Fracture images of (a) GFA-4-12-15, (b) GFB-4-12-15, and (c) GFC-4-12-15 glass-flax samples.
Figure 4
Figure 4
Bearing stress evolution at increasing edge distance E for pin-loaded laminates with hole diameter D = 4 mm and width W = 15 mm (W/D = 3.75) for all batches.
Figure 5
Figure 5
Stress-displacement curves at increasing aging time for pin-loaded laminates (D = 8 mm; E = 9 mm; and W = 15 mm).
Figure 6
Figure 6
Fracture images of (a) GFA-8-9-15, (b) GFB-8-9-15, and (c) GFC-8-9-15 glass-flax samples.
Figure 7
Figure 7
Bearing stress evolution at increasing edge distance E for pin-loaded laminates with hole diameter D = 8 mm and width W = 15 mm for all batches.
Figure 8
Figure 8
Scheme of failure mechanisms evolution in bearing stress vs. edge distance E plot for all laminates.

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