DEVELOPMENT OF LONG FIBRE THERMOPLASTIC PELLETS FOR AEROSPACE NON-STRUCTURAL APPLICATIONS
Topic(s) : Manufacturing
Co-authors :
Pedro GALVEZ-HERNANDEZ (SPAIN), Eduardo MARTÍN PARADAS (SPAIN), Juan Manuel JIMÉNEZ , Begoña GALINDO -GALIANA , Antonio GONZALEZ JIMENEZ (SPAIN), Dario CRESPO (SPAIN), Irene PUJALTEAbstract :
Introduction
The use of thermoplastic composite (TPC) materials in the aerospace industry has seen an exponential growth over the last years due to their exceptional properties, such as increased recyclability, faster processing, and weldability [1]. TPCs have been proposed to substitute non-recyclable or heavier materials in a wide range of components, such as door hinges [2] or floor beams [3], achieving comparable mechanical properties as their metallic and thermoset composite counterparts.
The work presented here was performed within the context of the LIDER-BUS project aiming at increasing the sustainability and the manufacturing throughput of an helicopter bumper subjected to high impact loads and an elevated operating temperature. In this study, TPCs in the form of long-fibre pellets were developed and characterised prior to their processing via a cost-effective technology (e.g., thermoforming, injection or compression moulding) at further steps within the project.
Materials and methods
Eight types of thermoplastic pellets combining four polymers (polyamide 6 (PA6): Ultramid® B3S; polybutadiene-terephthalate (PBT): Ultradur® B2550; polycarbonate (PC); Makrolon® 2205 and polypropylene (PP): ISPLEN® 086Y3E) and two fibre lengths (8 and 12mm) were studied. The StarRov® 895-2400 glass fibre was selected to produce the PA6, PBT and PC pellets, whereas the PP pellets were reinforced with StarRov® 490.
The pellets were produced in a dedicated thermoplastic pultrusion line located at AIMPLAS, in which the polymer is melted in a twin-screw extruder and impregnates the glass fibre tow as it goes through an impregnation die. The produced reinforced thermoplastic rod is then cut into pellets of the desired length.
Following the manufacturing of the long-fibre pellets, a preliminary mechanical characterisation, comprising tensile (ISO 527), impact (ISO 179) and flexural testing (ISO 14125), was conducted. Five specimens from each compound were used for each type of test. The specimens were machined from rectangular plaques produced via compression moulding of the obtained pellets.
Results
PA6-based pellets provided the highest values for the tensile strength (σy) and Young´s modulus (E) at 8mm (σy: 41.5 ± 7.5 MPa; E: 7900 ± 1240 MPa) and 12mm (σy: 57.1 ± 7.1 MPa; E: 8780 ± 460 MPa) (Figure 1a). Regarding the flexural characterisation, PA6 pellets showed the highest flexural strength (8 mm: 136 ± 9 MPa; 12mm: 133 ± 21 MPa), whereas the PC 12mm-pellet exhibited the highest flexural modulus at 6950 ± 1270 MPa), although closely followed by the PA6 and PBT reinforced pellets (Figure 1b). Finally, PC-8mm fibre showed the highest energy absorption at 280 ± 90 kJ/m2, which is a 70% higher than PP-8mm value of 81 ± 35 kJ/m2 (Figure 2). Additionally, PA6 exhibited the second and third higher values in terms of energy absorption (8mm: 220 ± 110 kJ/m2; 12mm: 230 ± 50 kJ/m2).
The use of thermoplastic composite (TPC) materials in the aerospace industry has seen an exponential growth over the last years due to their exceptional properties, such as increased recyclability, faster processing, and weldability [1]. TPCs have been proposed to substitute non-recyclable or heavier materials in a wide range of components, such as door hinges [2] or floor beams [3], achieving comparable mechanical properties as their metallic and thermoset composite counterparts.
The work presented here was performed within the context of the LIDER-BUS project aiming at increasing the sustainability and the manufacturing throughput of an helicopter bumper subjected to high impact loads and an elevated operating temperature. In this study, TPCs in the form of long-fibre pellets were developed and characterised prior to their processing via a cost-effective technology (e.g., thermoforming, injection or compression moulding) at further steps within the project.
Materials and methods
Eight types of thermoplastic pellets combining four polymers (polyamide 6 (PA6): Ultramid® B3S; polybutadiene-terephthalate (PBT): Ultradur® B2550; polycarbonate (PC); Makrolon® 2205 and polypropylene (PP): ISPLEN® 086Y3E) and two fibre lengths (8 and 12mm) were studied. The StarRov® 895-2400 glass fibre was selected to produce the PA6, PBT and PC pellets, whereas the PP pellets were reinforced with StarRov® 490.
The pellets were produced in a dedicated thermoplastic pultrusion line located at AIMPLAS, in which the polymer is melted in a twin-screw extruder and impregnates the glass fibre tow as it goes through an impregnation die. The produced reinforced thermoplastic rod is then cut into pellets of the desired length.
Following the manufacturing of the long-fibre pellets, a preliminary mechanical characterisation, comprising tensile (ISO 527), impact (ISO 179) and flexural testing (ISO 14125), was conducted. Five specimens from each compound were used for each type of test. The specimens were machined from rectangular plaques produced via compression moulding of the obtained pellets.
Results
PA6-based pellets provided the highest values for the tensile strength (σy) and Young´s modulus (E) at 8mm (σy: 41.5 ± 7.5 MPa; E: 7900 ± 1240 MPa) and 12mm (σy: 57.1 ± 7.1 MPa; E: 8780 ± 460 MPa) (Figure 1a). Regarding the flexural characterisation, PA6 pellets showed the highest flexural strength (8 mm: 136 ± 9 MPa; 12mm: 133 ± 21 MPa), whereas the PC 12mm-pellet exhibited the highest flexural modulus at 6950 ± 1270 MPa), although closely followed by the PA6 and PBT reinforced pellets (Figure 1b). Finally, PC-8mm fibre showed the highest energy absorption at 280 ± 90 kJ/m2, which is a 70% higher than PP-8mm value of 81 ± 35 kJ/m2 (Figure 2). Additionally, PA6 exhibited the second and third higher values in terms of energy absorption (8mm: 220 ± 110 kJ/m2; 12mm: 230 ± 50 kJ/m2).