Multimaterial Extrusion‐Based Additive Manufacturing of Compliant Crack Arrester: Influence of Interlayer Length, Thickness, and Applied Strain Rate

Abstract

Additive manufacturing is a useful tool for fabricating complex multimaterial structures. Compliant interlayers (ILs) can easily be introduced into stiff materials to increase toughness and stop or impede crack growth, as is done in nature. The aim herein is to analyze the influence of varying IL lengths and thicknesses on crack propagation in 3D‐printed polymers at different loading rates. A glycol‐modified poly(ethylene terephthalate) is used as a matrix material, while a thermoplastic elastomer on a copolyester basis serves as an compliant IL. Specimen fabrication is done with a fused filament fabrication 3D printer equipped with a multimaterial unit, which allows to print a component composed of several materials within one print. Additively manufactured Charpy samples are tested in three‐point bending at loading rates between 0.1 mm min−1 and 3.8 m s−1. The thickness of the IL almost shows no effect on energy absorption as long as remaining in the same printing orientation and loading rate. For varying IL lengths, a constant fight between crack penetration and crack deflection occurs. At low loading rates, the IL acts as a defect. As the loading rate increases, the total absorbed energy of composites increases compared with the pure matrix material.

3D Printing of Flow‐Inspired Anisotropic Patterns with Liquid Crystalline Polymers

“…[ 8 ] For instance, tailoring such stiffness gradients allows the development of single‐material bio‐inspired crack‐arresters similar to those obtained by alternating stiff and soft polymeric layers. [ 51 ] The explored range of stiffness in our work opens new paths for tuning compliance and deformation before failure on the fly, simply by changing the processing conditions of the polymer.…”

Synergistic Toughening of Epoxy through Layered Poly(ether imide) with Dual-Scale Morphologies

“…On the contrary, at higher cure temperatures, less connectivity was observed due to the higher frequency of smaller particles than bigger particles (Figure b), which can lead to a weaker interface. The strong interface between big epoxy particles and PEI formed at lower cure temperatures showed enhanced crack growth resistance due to the different energy-dissipating mechanisms, such as crack deflection and delamination . A crack generally propagates in the direction of the least resistance.…”

“…The strong interface between big epoxy particles and PEI formed at lower cure temperatures showed enhanced crack growth resistance due to the different energy-dissipating mechanisms, such as crack deflection and delamination. 32 A crack generally propagates in the direction of the least resistance. Therefore, at lower temperatures, the crack prefers to propagate around the interface instead of propagating through the interface due to the weak adhesion (Figure 9a,b), which results in a larger distance covered by the crack (i.e., higher crack tortuosity).…”

Multi-Material 3D Printing of Biobased Epoxy Resins

“…The proportions of D1 enhance stiffness and strength but adversely affect elongation at break. In particular, the embedding of a soft interlayer into a stiff matrix, as in the case of D1-E1-D1, has been shown in various publications [60][61][62][63][64] to have a positive effect on toughness enhancement. However, this effect did not manifest here, likely due to an insufficient mismatch in mechanical properties.…”