Experimental Characterization and Analysis of the In-Plane Elastic Properties and Interlaminar Fracture Toughness of a 3D-Printed Continuous Carbon Fiber-Reinforced Composite

Abstract

The use of continuous fiber as reinforcement in polymer additive manufacturing technologies enhances the mechanical performance of the manufactured parts. This is the case of the Carbon-Fiber reinforced PolyAmide (CF/PA) used by the MarkForged MarkTwo® 3D printer. However, the information available on the mechanical properties of this material is limited and with large variability. In this work, the in-plane mechanical properties and the interlaminar fracture toughness in modes I and II of Markforged’s CF/PA are experimentally investigated. Two different standard specimens and end-tabs are considered for the in-plane properties. Monolithic CF/PA specimens without any additional reinforcement are used for the interlaminar fracture toughness characterization. Two different mode I specimen configurations are compared, and two different test types are considered for mode II. The results show that prismatic specimens with paper end-tabs are more appropriate for the characterization of the in-plane material properties. The use of thick specimens for mode I fracture toughness tests complicates the characterization and can lead to erroneous results. Contrary to what has been reported in the literature for the same material, fracture toughness in mode I is lower than for mode II, which agrees with the normal tendency of traditional composite materials.

Interlaminar and translaminar fracture toughness of 3D‐printed continuous fiber reinforced composites: A review and prospect

“…Concerning the characterization of the mode II interlaminar fracture toughness of 3D-printed CFRCs, the ASTM D7905 and ISO 15114 standards have been adopted. 23,39 The end-notched flexure (ENF) test described in the ASTM D7905 standard (shown in Figure 4C) was used to obtain the fracture toughness at crack initiation. The calibrated end-loaded Split (C-ELS) test described in the ISO 15114 standard (shown in Figure 4B) was used to characterize fracture toughness at both crack initiation fracture toughness G (I) and crack propagation fracture toughness G (P) .…”

“…For 3D-printed CFRCs, research in terms of translaminar fracture toughness focused on the mode I translaminar fracture toughness. According to the ASTM D5045 Translaminar ASTM D5045 [47,48] ASTM E1922-04 [49] ASTM STP 410 [50] Mode II Interlaminar ASTM D7905 [24,37,40,51] ISO 15114 [39,40,42] Mixed mode Interlaminar ASTM D6671 [40] standard, the compact tension (CT) was used to characterize mode I fracture toughness. 47 In addition, testing of semi-circular Bending (SCB) specimens and double edge notch tension (DET) specimens could also be applied to characterize mode I fracture toughness in 3D-printed continuous fiber reinforced specimens.…”

“…Lamin et al 50 studied mode I translaminar fracture toughness of DET specimens with unidirectional F I G U R E 8 R-curves for Mode I interlaminar fracture toughness of 3D-printed CFRCs: (A) 0 /0 (left) and +45 /À45 (right) interfaces, 58 (B) 0 /15 (left), +15 /À15 (center), and +30 /À30 (right) interfaces. 59 and cross-ply lay-up configuration by tensile test (shown in Figure 10A). Onyx and continuous carbon fibers (glued by polyamide), supplied by Markforged, were employed in specimen production.…”

“…F I G U R E 9The crack propagation in (A) multidirectional DCB samples: smooth propagation (up), crack jumping (middle), and crack branching (down),59 (B) DCB specimens: delamination migration,58 (C) unreinforced (up) and reinforced (down) SCB specimens,57 and (D) single-edge notch specimens 49. …”

Tensile Performances of Continuous Fiber Reinforced Thermoplastic Composites with holes processed by 3D Printing, Laser and Drilling

“…The 3D printer for composites named Mark One reduces the cost by 70% and increases the printing speed by 90% when compared with the resin transfer molding [7]. The printer for CFRTPCs called Mark Two can print continuous Kevlar/glass/carbon fiber reinforced thermoplastic composites and the printing speed is 40% faster than that of Mark One [8].…”