Abstract
This study experimentally investigated the effects of nanomaterials and interface fiber angle on the mode I fracture toughness of woven carbon fiber-reinforced polymer (CFRP) composites. Three different types of nanomaterials were used: COOH-functionalized short multi-walled carbon nanotubes (S-MWCNT-COOH), multi-walled carbon nanotubes (MWCNTs), and graphene nanoplatelets (GnPs). Double cantilever beam specimens were composed of 12 woven carbon fiber fabrics with/without 1 wt% nanomaterials, and were manufactured using the hand lay-up method. Furthermore, two different stacking sequence series were used; the first series comprised only on-axis carbon-fiber fabrics (0° or 90°), and the second series comprised both on- and off-axis carbon-fiber fabrics (0° or 90° and ±45°). The test results showed that adding S-MWCNT-COOH, MWCNTs, and GnPs significantly increased the mode I fracture toughness of the CFRP composites for both the stacking sequence series. Moreover, the specimens that used only on-axis carbon fiber fabrics exhibited higher fracture toughness values than those of the specimens that used on- and off-axis carbon fiber fabrics together. In addition, an empirical model was established to predict the fracture toughness of the CFRP composites with nanomaterials by using on- and off-axis carbon fiber fabrics together, and the prediction results showed a good agreement with the experimental results.
Highlights
The use of fiber reinforced polymer (FRP) composites has been widely increased in the field of civil and architectural engineering because of their high strength and stiffness
The test results showed that the fracture toughness of S-multi-walled carbon nanotubes (MWCNTs)-COOH-CFRP0-0 and MWCNT-CFRP0-0 did not show significant difference. This is because the magnitude of fracture toughness of carbon fiber-reinforced polymer (CFRP) composites incorporating carbon nanotubes (CNTs) is dependent on the failure mechanism, which depends on the CNT length, and the critical length of CNTs embedded in the epoxy matrix [44]
The failure index of the test specimens with the interface fiber angle of 0//45 proposed to be 0.70 for all the types of nanomaterials. This value of 0.70 is lower than 1.32, was proposed to be 0.70 for all the types of nanomaterials. This value of 0.70 is lower than which was suggested by Zhao et al [30], as the materials and stacking sequences used to fabricate double cantilever beam (DCB)
Summary
The use of fiber reinforced polymer (FRP) composites has been widely increased in the field of civil and architectural engineering because of their high strength and stiffness. From previous studies [12,13,14,15,16,17,18,19], it was observed that using additive materials such as thermoplastic resins, rubber, and nanoparticles (or nanomaterials) into matrix could considerably enhance the toughness of the matrix, thereby improving the fracture toughness of FRP because of the increased interlaminar strength. In other research works [23,24,25], nanomaterials such as carbon nanotubes (CNTs) and carbon nanofibers were introduced to enhance the fracture toughness of polymer matrices This is because the nanomaterials that have high stiffness and strength play a role as reinforcement materials, which leads to an enhancement in the mechanical performance of composites. An empirical model was proposed for predicting the mode I fracture toughness of CFRP composites incorporating nanomaterials with both on- and off-axis carbon fiber fabrics
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