Open Access Open Access  Restricted Access Subscription Access

Multiscale Damage in Co-Cured Composites—Perspectives from Experiments and Modelling



Bonded and co-cured composites are popular alternatives to structures joined with mechanical fasteners in aircraft but the complex and coupled damage mechanisms in the co-cured/bonded region are poorly understood, thus making the evaluation of their strength and durability difficult with current modelling strategies. This study explores the potential of interleaf inclusion in failure-prone, critical regions of co-cured composite specimens in improving the joint strength and interface fracture toughness and strives to advance the understanding of damage initiation in the co-cured region using an atomistic model. A two-pronged approach is pursued here with bench-scale experimental testing and molecular modelling in this study. Experiments are performed for mode I fracture toughness with double cantilever beam (DCB) on composite laminates with an epoxy interleaf layer. Two epoxy resins and three methods for interleaf inclusion are explored in this study; we supplement the results from DCB testing with insights from confocal microscopy on the crack tip and the interleaf layer pre- and post-testing. Molecular dynamic (MD) simulations capture the cohesive interactions at the threephase interface containing the carbon fiber, the prepreg epoxy, and the interleaf epoxy. Results highlight that an interleaf layer made from partially-cured and filmed epoxy, further consolidated in the composite lay-up is the most effective way to suppress void formation, improve dispersion, and maximize cohesive interactions at the interface of co-cured composites.


Full Text:



Rottler J, Barsky S, Robbins MO. Cracks and Crazes: On Calculating the Macroscopic Fracture

Energy of Glassy Polymers from Molecular Simulations. Phys Rev Lett 2002;89:148304.

Naebe M, Abolhasani MM, Khayyam H, Amini A, Fox B. Crack Damage in Polymers and

Composites: A Review. Polym Rev 2016;56:31–69.

Awaja F, Zhang S, Tripathi M, Nikiforov A, Pugno N. Cracks, microcracks and fracture in

polymer structures: Formation, detection, autonomic repair. Prog Mater Sci 2016;83:536–73.

Karger-Kocsis J. Microstructural and molecular dependence of the work of fracture parameters in

semicrystalline and amorphous polymer systems. Eur. Struct. Integr. Soc., vol. 27, Elsevier; 2000,

p. 213–30.

Johnson W, Masters J, O’Brien T, O’Brien T, Martin R. Round Robin Testing for Mode I

Interlaminar Fracture Toughness of Composite Materials. J Compos Technol Res 1993;15:269.

Tanimoto T. Interleaving methodology for property tailoring of CFRP laminates. Compos

Interfaces 2002;9:25–39.

Ozdil F, Carlsson LA. Mode I Interlaminar Fracture of Interleaved Graphite/Epoxy. J Compos

Mater 1992;26:432–59.

Chen SF, Jang BZ. Fracture behaviour of interleaved fiber-resin composites. Compos Sci Technol


Zhou H, Du X, Liu H-Y, Zhou H, Zhang Y, Mai Y-W. Delamination toughening of carbon

fiber/epoxy laminates by hierarchical carbon nanotube-short carbon fiber interleaves. Compos Sci

Technol 2017;140:46–53.

Meijer G, Ellyin F. Effect of a Soft Interleaf on Transverse Cracks in Thick Glass Fiber–Epoxy

Cross-ply Laminates. J Compos Mater 2004;38:2199–211.

Jiang W, Tjong SC, Chu PK, Li RKY, Kim JK, Mai YW. Interlaminar Fracture Properties of

Carbon Fibre/Epoxy Matrix Composites Interleaved with Polyethylene Terephthalate (Pet) Films.

Polym Polym Compos 2001;9:141–5.

Yun NG, Won YG, Kim SC. Toughening of carbon fiber/epoxy composite by inserting

polysulfone film to form morphology spectrum. Polymer 2004;45:6953–8.

Palazzetti R, Zucchelli A, Gualandi C, Focarete ML, Donati L, Minak G, et al. Influence of

electrospun Nylon 6,6 nanofibrous mats on the interlaminar properties of Gr–epoxy composite

laminates. Compos Struct 2012;94:571–9.

Marino SG, Czél G. Improving the performance of pseudo-ductile hybrid composites by filminterleaving.

Compos Part Appl Sci Manuf 2021;142:106233.

Shin YC, Lee WI, Kim HS. Mode II interlaminar fracture toughness of carbon nanotubes/epoxy

film-interleaved carbon fiber composites. Compos Struct 2020;236:111808.

Singh S, Partridge IK. Mixed-mode fracture in an interleaved carbon-fibre/epoxy composite.

Compos Sci Technol 1995;55:319–27.

Zheng N, Liu H-Y, Gao J, Mai Y-W. Synergetic improvement of interlaminar fracture energy in

carbon fiber/epoxy composites with nylon nanofiber/polycaprolactone blend interleaves. Compos

Part B Eng 2019;171:320–8.

Reichanadter A, Bank D, Mansson JE. A novel rapid cure epoxy resin with internal mold release.

Polym Eng Sci 2021;61:1819–28.

Bhowmik R, Katti KS, Katti D. Molecular dynamics simulation of hydroxyapatite–polyacrylic

acid interfaces. Polymer 2007;48:664–74.

Subramanian N, Koo B, Venkatesan KR, Chattopadhyay A. Interface mechanics of carbon fibers

with radially-grown carbon nanotubes. Carbon 2018;134:123–33.

Subramanian N, Whittaker ML, Ophus C, Lammers LN. Structural Implications of Interfacial

Hydrogen Bonding in Hydrated Wyoming-Montmorillonite Clay. J Phys Chem C


Subramanian N, Rai A, Chattopadhyay A. Atomistically derived cohesive behavior of interphases

in carbon fiber reinforced CNT nanocomposites. Carbon 2017;117:55–64.

Subramanian N, Rai A, Chattopadhyay A. Atomistically informed stochastic multiscale model to

predict the behavior of carbon nanotube-enhanced nanocomposites. Carbon 2015;94:661–72..

Plimpton S. Fast Parallel Algorithms for Short-Range Molecular Dynamics. J Comput Phys


Raimondo A, Urcelay Oca I, Bisagni C. Influence of interface ply orientation on delamination

growth in composite laminates. J Compos Mater 2021.


  • There are currently no refbacks.