Identifying the sensitivities of transverse cracking in composites

Fiber-reinforced composites are widely used in aerospace and other high-tech industries. Understanding how their microstructure and the strength of the fiber-matrix interfaces affect their failure properties can lead to manufacturing stronger materials. A recent study at the University of Illinois at Urbana-Champaign developed a model to identify the sensitivities of transverse cracking, one of the key failure processes present in composite laminates, on details of the composite microstructure.

Composite laminates used in aerospace application are typically made of layers of carbon fibers with varying orientations embedded in epoxy. For example, the composite laminate can be composed of a carbon/epoxy layer with the fibers oriented in the 90-degree direction sandwiched between two 0-degree plies. The fibers are each about seven microns in diameter, or about one-seventh of the thickness of a human hair.

Transverse cracking of composite laminate
Left: Optical image of a composite laminate used in the transverse failure experiments. Right: Representative image of a transverse crack spanning the 90 ply. As apparent from this optical image, the transverse cracks extend primarily along fiber/matrix interfaces. Credit: University of Illinois

We know from experiments that cracks propagate transversely across the 90-degree plane, then stop when they reach the interfaces with the 0-degree plies. So we developed a method that allows us to simulate hundreds of fibers in a realistic system and study how the failure response is affected if we change the location of a single fiber or of many fibers, or the strength of the interface,” said Philippe Geubelle, a professor in the Department of Aerospace Engineering.

In this new method, optical micrographs are taken of the 90-degree ply and the location of all of the fibers are extracted to construct a realistic computational model of the ply. Similar studies have been limited to tens of fibers.

With the special finite element method we have developed to simulate the transverse cracking of the 90-degree ply, we can simulate hundreds of fibers,” Geubelle said. “The most we’ve done so far is close to 3,000 fibers. Because the crack propagates primarily along the fiber-matrix interfaces, our model emphasizes the cohesive failure of these interfaces,” he said. “In addition, we have developed the ability to extract efficiently the sensitivity of the failure event with respect to the properties of the microstructure. These properties include the location and size of the fibers, and the failure properties of the fiber-matrix interfaces. We can also compute the sensitivity of the failure event with respect to the parameters (average, standard deviation, etc.) that define the distribution of these microstructural parameters.”

The model is validated against experimental observations performed in Prof. Nancy Sottos’s group in the Department of Materials Science and Engineering at the University of Illinois.

Of course, you could get these sensitivities experimentally, with every conceivable variation, to see what the effect is on the failure event,” Geubelle said. “To do this numerically is much more efficient.”

The work is supported by a grant from the Center of Excellence on Integrated Multiscale Modeling with funds from the Air Force Research Laboratory and the Air Force Office of Scientific Research, in collaboration with researchers from Johns Hopkins University and the University of California, Santa Barbara.

 

Source: University of Illinois – Aerospace Engineering


Leggi anche

Sustainable Composites logo

Una nuova iniziativa per affrontare il problema del riutilizzo e del riciclo dei materiali compositi alla fine del loro ciclo di vita prende il via nel Regno Unito, sotto la guida del National Composites Centre (NCC) e del Center for Process Innovation (CPI).
Da questa iniziativa, denominata Sustainable Composites, dovrebbe nascere la prossima generazione di materiali compositi eco-compatibili, grazie a una partnership tra industria, mondo accademico e governo che sfrutterà la ricerca e lo sviluppo tecnologico dei compositi nel Regno Unito …

Leggi tutto…

La Graduate School of Engineering della Tohoku University, la Graduate School of Information Sciences e NEC Corporation stanno lavorando insieme a un sistema integrato in grado di accelerare lo sviluppo della plastica rinforzata con fibra di carbonio (CFRP) per strutture aeronautiche…

Leggi tutto…

CETMA - Thermal imaging camera applied to an induction welding process

Il progetto europeo DEWTECOMP, coordinato dal CETMA, ha come obiettivo lo sviluppo di un sistema di saldatura a induzione finalizzato a ottenere un innovativo ed efficiente sistema di adesione strutturale delle parti di rinforzo (quali fazzoletti, zeppe, raccordi) ai telai strutturali per realizzare una struttura perimetrale altamente integrata (DSS-Door Surround Structure)…

Leggi tutto…

NUST MISIS presentation of aluminum matrix composites

Gli scienziati dei materiali dell’Università Nazionale di Scienza e Tecnologia MISIS, in Russia, hanno presentato una nuova tecnologia per la produzione di compositi a matrice di alluminio da nuove materie prime, polveri composite per la stampa 3D di componenti per aeromobili e autovetture. Il nuovo metodo aumenta del 40% l’uniformità delle proprietà e la durezza dei compositi ottenuti rispetto agli analoghi prodotti in maniera standard…

Leggi tutto…

Access panel in recycled thermoplastic composites

All’interno del progetto TPC-Cycle recycling, è stato sviluppato un pannello di accesso per aeromobili in materiale composito termoplastico riciclato ed è stato testato con successo in volo. Il pannello è stato ottenuto utilizzando un nuovo processo di riciclaggio, che ha permesso di rendere il componente più leggero e meno costoso rispetto ai pannelli standard…

Leggi tutto…