Flexural Fatigue in a Polymer Matrix Composite Material Reinforced with Continuous Kevlar Fibers Fabricated by...

Area of Science:

• Materials Science
• Mechanical Engineering
• Additive Manufacturing

Background:

• Polymer matrix composites reinforced with continuous Kevlar fibers are increasingly used in demanding applications.
• Additive manufacturing techniques like Fused Filament Fabrication (FFF) offer novel ways to produce these complex materials.
• Understanding the fatigue behavior of such materials is crucial for predicting their service life and ensuring structural integrity.

Purpose of the Study:

• To investigate the fatigue bending performance of Kevlar-fiber-reinforced polymer composites fabricated via FFF.
• To develop and validate a numerical model capable of predicting the fatigue life of these composite materials.
• To analyze the failure mechanisms at the microstructural level.

Main Methods:

• Fatigue bending tests were conducted under controlled displacement on FFF-printed Kevlar composites.
• Static characterization determined the material's flexural modulus (4.73 GPa) and strength (110 MPa).
• Two numerical models were employed: one with orthotropic properties for static analysis and another with isotropic properties for fatigue modeling.

Main Results:

• Fatigue failure occurred between 15 and 711 cycles for applied loads ranging from 84.7% to 92.3% of static flexural displacement.
• The numerical model using isotropic in-bulk properties successfully reproduced the experimental fatigue behavior.
• Morphological analysis revealed failure modes including fiber breakage, tearing, buckling, matrix cracking, and porosity.

Conclusions:

• The FFF-fabricated Kevlar composites exhibit limited fatigue life under the tested conditions.
• Isotropic material properties are sufficient for accurately modeling the fatigue response of these composites.
• Microstructural defects significantly influence the fatigue failure mechanisms of the material.