Ex-situ method for toughening glass/epoxy composites by interlaminar films made of polyetherketone cardo and calcium sulfate whisker

Abstract

Epoxy matrix composites were toughened by introducing films into fiberglass fabric layers based on an ex-situ vacuumassisted resin transfer molding technique. The mixture films were made of a certain polyetherketone cardo and calcium sulfate whiskers with different mass percent. The toughening mechanism was studied by dynamic mechanical thermal analysis and scanning electron microscopy. The addition of calcium sulfate whisker changed glass transition temperatures of Epoxy Resin (EP) and polyetherketone cardo, indicating that films with calcium sulfate whisker were melting during the curing of epoxy resin and forming the mixture of EP phase, polyetherketone cardo phase, and calcium sulfate whisker between the layers of composites. Meanwhile, the results indicated that calcium sulfate whiskers and fiberglass fabric formed three-dimensional structure between the layers of composites to toughen the composites. The results of the mechanical properties show that the interlaminar shear strength and fracture toughness (G IC ) were obviously improved meanwhile tensile strength and flexural strength kept stable whether the addition of films or not. Maximum values of the interlaminar shear strength and fracture toughness (G IC ) were 22% and 95% higher than that of the controlled specimens without films, respectively. The interlaminar mechanical properties improved with the addition of films made of polyetherketone cardo and calcium sulfate whisker, which is benefit for the improvement of whole mechanical properties and wide usage of laminate composites.

Toughening Behavior of Carbon/Epoxy Laminates Interleaved by PSF/PVDF Composite Nanofibers

“…On the other side, its highly crosslinked structure leads to brittleness and thus to poor resistance to crack propagation [1,2]. Among the several methods that have been presented during the years to increase the fracture toughness of carbon/epoxy laminates [3][4][5][6], interleaving polymers [7][8][9], in the form of particles, films, or nanofibrous mats [10][11][12][13][14][15][16], has proved to be one of the most effective. In particular, nanofibrous mats have been found to be a suitable choice because of their high porosity (which lead to rapid penetration of epoxy) and the strengthening effects they are able to provide.…”

Investigation on interlayer phase morphology evolution of “Ex‐Situ” toughened composite laminate

“…Initially, the toughening thermoplastic (TP) films were inserted into the interlaminar domains of TS prepreg or TP solution was directly sprayed onto the surface of TS prepreg, whereby small TS molecules would diffuse into the interlayer and blended with TP resin. Then, the phase‐separated microstructures were formed in the interlayer during the polymerization‐induced phase separation process (PIPS), which could absorb a large amount of crack energy . Obviously, the innovative “ Ex‐Situ ” technology could not only maintain the excellent in‐plane mechanical properties but also improved the interlaminar fracture toughness of the laminates.…”

Finding the best sequence in flexible and stiff composite laminates interleaved by nanofibers

“…Toughening thermoset composite laminates is one the most common methods for increasing the strength of these materials against delamination, especially under fatigue and impact loadings. 1 Different material types: (1) particle, [2][3][4][5][6][7][8][9][10][11] (2) film, [12][13][14][15][16] or (3) polymeric nanofiber [17][18][19][20][21][22][23][24] and methods: (1) mixing with the matrix before fabricating the sample [25][26][27][28][29] and (2) interleaving [30][31][32][33][34][35][36] have been introduced for this aim. All these methods and material types have their own advantages or disadvantages; for example, using nanoparticles as the toughener can incredibly increase fracture toughness; 6 but in practical applications, it can be very complicated.…”