FUSED FILAMENT MANUFACTURING OF BIOINSPIRED CARBON FIBER REINFORCED POLYMERS
Topic(s) : Manufacturing
Co-authors :
Carlos IZQUIERDO MARTÍN (SPAIN), Saber MAAMRI (SPAIN), María Elena HERNÁNDEZ GARCÍA , Leticia AGUADO FERREIRA , Roberto GUZMÁN DE VILLORIA , Jorge BAUTISTA PÉREZAbstract :
The great strength-weight relationship of carbon fiber reinforced polymers (CFRP) is the reason for what they are increasingly used in industry. The high mechanical properties of these materials are limited by their tendency to delamination and catastrophic failure, which causes their behaviour before failure to be fundamentally elastic, without plastic deformation that serves as an alarm. There is practically no energy absorption before breaking and the impact resistance is very low. For all these reasons, currently, the transportation industry has been demanding a new generation of CFRP that improves these limitations, that is, a new CFRP material that does not present this great difficulty in detecting the internal damage that triggers catastrophic failure and that limits its applications so much.
Currently, strategies such as z-pinning, the introduction of 3D fabrics, stitching, bio-insipiration, etc. have already been developed to improve interlaminar properties and although their validity has been demonstrated in many cases, the way to scale them can be complicated. In this work, bioinspiration has been chosen as a technique to improve the properties of CFRP.
Biomimetics is presented as a good solution to eliminate these problems through relatively simple designs found in nature. The “brick and mortar” structure of nacre stands out, a material that has a great toughness-resistance relationship despite being made up of fragile aragonite platelets. High toughness is achieved due to the microstructure of the brick wall, consisting of a discontinuous design that agglomerates fragile platelets (bricks), which provide strength through a continuous matrix (mortar) that distributes the load between the different bricks and dissipates part of the energy.
This “brick and mortar” structure has been successfully implemented in thermoset CFRP [1], [2] by using manual and automated process. However, in order to take advantage of these structures in thermoplastic CFRP, other manufacturing techniques needs to be developed.
Here, a novel method is used through additive manufacturing with an FFF (Fused Filament Manufacturing) printer previously modified for printing with continuous CFRP. The method consists of the extrusion process of a continuous carbon fiber reinforced polymer filament to which cuts are made with the desired length of the brick simultaneously during printing. Specimens with different brick sizes (75, 50, and 25 mm length) have been manufactured and their morphology and tensile strength have been studied. In order to improve the properties of the samples, a post process technique [3] has also been evaluated.
Currently, strategies such as z-pinning, the introduction of 3D fabrics, stitching, bio-insipiration, etc. have already been developed to improve interlaminar properties and although their validity has been demonstrated in many cases, the way to scale them can be complicated. In this work, bioinspiration has been chosen as a technique to improve the properties of CFRP.
Biomimetics is presented as a good solution to eliminate these problems through relatively simple designs found in nature. The “brick and mortar” structure of nacre stands out, a material that has a great toughness-resistance relationship despite being made up of fragile aragonite platelets. High toughness is achieved due to the microstructure of the brick wall, consisting of a discontinuous design that agglomerates fragile platelets (bricks), which provide strength through a continuous matrix (mortar) that distributes the load between the different bricks and dissipates part of the energy.
This “brick and mortar” structure has been successfully implemented in thermoset CFRP [1], [2] by using manual and automated process. However, in order to take advantage of these structures in thermoplastic CFRP, other manufacturing techniques needs to be developed.
Here, a novel method is used through additive manufacturing with an FFF (Fused Filament Manufacturing) printer previously modified for printing with continuous CFRP. The method consists of the extrusion process of a continuous carbon fiber reinforced polymer filament to which cuts are made with the desired length of the brick simultaneously during printing. Specimens with different brick sizes (75, 50, and 25 mm length) have been manufactured and their morphology and tensile strength have been studied. In order to improve the properties of the samples, a post process technique [3] has also been evaluated.