PSI - Issue 34

Alexander Berndt et al. / Procedia Structural Integrity 34 (2021) 105–110 Author name / Structural Integrity Procedia 00 (2019) 000–000

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1. Introduction Despite an ongoing worldwide pandemic, the market for additive manufacturing is still growing Wohlers et al. (2021). Fused deposition modeling (FDM) is conventionally used as an additive manufacturing process. Commonly used materials include polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) Dey et al. (2019). More and more on the rise are fiber reinforced materials such as carbon fiber reinforced plastics (CFRPs) Palanikumar et al. (2020). Due to their mechanical properties, CFRPs are widely used in the fields of aerospace, automobile and medical engineering Joshi et al. (2015); Murr (2016); Zhang et al. (2021); Wang et al. (2017); Barrios -Muriel et al. (2020). In addition to the mechanical properties, the energy-absorbing properties of the materials in these areas are also crucial. Therefore, lightweight thin-walled structures have shown to be efficient energy absorbers Lu et al. (2003). Due to the restrictions of the FDM process, continuous fiber reinforced crash tubes can only be produced to a limited extent. The influence of print orientation and the direction of the fiber plies are decisive Di Angelo et al. (2020). The underlying study investigates the effect of fiber angle orientation on the specific energy absorption (SEA) capability of continuous carbon fiber (CCF) crash tubes. Enabling the materials strengths, a cylindrical fourth axis is implemented into a 3D printer, on to which the CFRP filament is printed.

Nomenclature ABS

acrylonitrile butadiene styrene

l 0

crush distance original mass number of layers polylactic acid

α

fiber angle

m 0

CCF

continuous carbon fiber

n

CFRPs continuous carbon fiber reinforced plastics

PLA SEA

d a d i

outer diameter inner diameter average force maximum force

specific energy absorption

t l

layer height

F avg F max

T p t w v p

print temperature wall thickness printing speed

FDM Fused deposition modeling

l i

initial length

2. Materials and methods 2.1. Specimen design

Continuous carbon fiber filament from Markforged was used to print tube shaped specimens. The material consists of a thermoplastic as a matrix material covering a 1K continuous carbon fiber roving. The layer height is t l = 0.125 mm. Each one of the crash tubes has a symmetrical layer setup [+α, - α ,0,0 ] s . There are eight layers in total, resulting in a wall thickness of t w = 1 mm. Due to planar printing onto a 3D shaped object, the printing design within the slicer software needs to be adapted. Figure 1 shows an example of the sliced 15° layup printing design in the AURA software of Anisoprint Anisoprint .

Figure 1. Sliced 15° fiber angle lay-up of crash tube