Interlaminar fracture and crack‐healing capability of carbon fiber/epoxy composites toughened with 3D‐printed poly‐ε‐caprolactone grid structures

Abstract

In this study, carbon fiber (CF)/epoxy (EP) composites are toughened with 3Dprinted poly-ε-caprolactone (PCL) grid structures which are produced by fused deposition modeling at three different areal weight densities and place between dry plain-weave carbon fabrics prior to resin infusion. Three-point bending, Mode-I fracture toughness, interlaminar shear strength (ILSS), and Charpy impact tests are carried out on the prepared composite specimens. The results show that the PCL interlayers can enhance Mode-I fracture toughness up to seven times (693%). The main toughening mechanism is the crack bridging due to the formation of PCL fibrils. It is shown that there is a quadratic relationship between the amount of PCL and Mode-I fracture toughness improvement. The thermal healing efficiencies (η) for the first and second healing of PCL reinforced composites are determined as 44.1% and 28.2%, respectively. DMA results indicates that the tanδ values are increased almost 10 times with the addition of PCL interlayers. The flexural properties are decreased due to the reduced fiber volume fraction, higher void content, and plasticization effect of PCL interlayers.

A Novel Method to Quantify Self-Healing Capabilities of Fiber-Reinforced Polymers

“…No matter what the self-healing approach is, apart from the main challenge of maintaining a high volume fraction of the reinforcing fibers and adequate mechanical properties for the healable composite, another critical point is represented by the difficulty in finding a common healing efficiency testing method, shared among all the scientific community. The most frequently adopted test methods are either nondestructive analysis, such as C-scans, or are based on mechanical tests such as Mode I double cantilever beam (DCB), tapered double cantilever beam (TDCB), Mode II end-notched flexure (ENF) testing, compression after impact (CAI), bending after indentation, fatigue, and tensile, and bending testing (Tesoro and Sastri, 1990;Meure et al, 2009;Park et al, 2009;Williams et al, 2009;Patrick et al, 2014;Luterbacher et al, 2015;Manfredi et al, 2015;Hia et al, 2016;Lucas et al, 2016;Sordo and Michaud, 2016;Zhang and Li, 2016;Michaud, 2017a, 2017b;Cohades et al, 2018;Hostettler et al, 2019;Kanu et al, 2019;Beylergil, 2021;Kamble et al, 2021;Jony et al, 2022;Kamble et al, 2022).…”

“…In Mode I DCB and Mode II end-notched flexure (ENF) testing, the composite samples undergo loading-unloading cycles that allow to record force-displacement curves and crack advancement. Healing efficiency can then be defined on stiffness-based or interlaminar fracture toughness calculations (Cohades and Michaud, 2017b) (Meure et al, 2009;Patrick et al, 2014;Cohades and Michaud, 2017b;Beylergil, 2021).…”

Effects of silane‐modified nano‐CaCO3 particles on the mechanical properties of carbon fiber/epoxy (CF/EP) composites

“…Compared to the reference specimens, there are only a few load drops since the crack propagates suddenly in these composites. [ 43 ] The crack extends more than 10 mm in one jump. It can be concluded that the crack propagation in neat nano‐CaCO 3 reinforced composites was unstable.…”

Enhancing Mode-I and Mode-II fracture toughness of carbon fiber/epoxy laminated composites using 3D-printed polyamide interlayers

“…Szebényi et al 55 utilized 3D-printed polycaprolactone (PCL) interlayers with various geometries on CF/EP prepregs, significantly increasing the composites' ductility. Beylergil 56 also demonstrated a nearly sevenfold increase in Mode-I fracture toughness of CF/EP composites using 3D-printed PCL interlayers. FDM offers opportunities in interface engineering with various polymers, including PA, which shows great promise for enhancing the mechanical properties of CF/EP composites.…”