skip to main content

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Effect of nanoscale interface modification on residual stress evolution during composite processing
The interface characteristics of the matrix and fibers significantly influence the evolution of residual stress in composite materials. In this study, we provide a methodology for reducing the residual stress in laminated composites by modifying the thermomechanical properties at the fiber–matrix interface. A hydrothermal chemical growth method was used to grow Zinc Oxide nanowires on the carbon fibers. We then utilized a novel digital image correlation approach to evaluate strains and residual stresses, in situ, throughout the autoclave curing of composites. We find that interface modification results in the reduction of residual stress and an increase in laminate strength and stiffness. Upon growing ZnO NWs on the carbon fibers, the maximum in situ in-plane strain components were reduced by approximately 55% and 31%, respectively, while the corresponding maximum residual stresses were decreased by 50.8% and 49.33% for the cross-play laminate [0°/90°] layup in the x and y directions, respectively. For the [45°/-45°] angle ply layup in the x-direction, the strain was decreased by 27.3%, and the maximum residual stress was reduced by 41.5%, whereas in the y-direction, the strain was decreased by 166.3%, and the maximum residual stress was reduced by 17.8%. Furthermore, mechanical testing revealed that the tensile strength for the [45°/-45°] and [0°/90°] laminates increased by 130% and 20%, respectively, with the interface modification.  more » « less
Award ID(s):
2001038
PAR ID:
10426560
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Journal of Composite Materials
ISSN:
0021-9983
Page Range / eLocation ID:
002199832311795
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ( , Journal of Composite Materials)
    Residual stresses are detrimental to composite structures as they induce processing defects like debonding, delamination, and matrix cracking which significantly decrease their load-bearing capability. In this research, a new in-situ approach using digital image correlation is utilized to analyze the effect of the cure cycle modification on residual stress evolution during processing. It was found that the modified cure cycle comprising abrupt cooling after gelation reduces the residual stresses. Five different layup configurations are investigated to examine the effect of fiber direction. A maximum average residual stress reduction of 31.8% is observed for the balanced unsymmetric [30/-30/60/-60] laminate. The residual stress reduction results in an increase in failure strength between 4 and 12% in the different layups and can lead up to a 22% increase in first-ply failure strength. 
    more » « less
  2. ; ( , Journal of Composite Materials)

    An experimental study is preformed to investigate the in-situ damage sensing capabilities of intra-ply hybrid carbon/glass laminate and epoxy composites under quasi-static interlaminar shear loading. A three-dimensional electrical sensory network is generated inside the composites through embedded carbon nanotubes (CNTs) in an epoxy matrix along with the carbon fibers in the intra-ply hybrid laminates. CNTs are dispersed in the epoxy matrix using a combination of ultrasonication and shear mixing techniques. Four circumferential ring probes are used to examine the electrical response under interlaminar shear load. The effect of four different intra-ply orientations (((0–90)C, where carbon fibers are oriented along the loading direction), ((0–90)G, where glass fibers are oriented along the loading direction), ((45/−45, where glass and carbon fibers are oriented at 45o/−45oand the laminates are repeated), and ((45/−45)A, where glass and carbon fibers are oriented at 45o/−45oand the laminates are alternated)) on the shear constitutive behavior and the damage detection are discussed. Intra-ply orientations of (45/−45) and (45/−45)Ashowed higher interlaminar shear strength and shear strain at break compared to (0/90)Cand (0/90)Gorientations. Out of all four orientations, (45/−45)Aprovided a better resolution of electrical response for damage sensing applications.

     
    more » « less
  3. ; ( , Journal of Composite Materials)

    A comprehensive experimental investigation is performed to understand the damage sensing capabilities of thermoplastic intra-ply carbon/glass laminated composites embedded with Carbon Nanotubes (CNTs) under quasi-static interlaminar shear and mode-I fracture loading conditions. CNTs are dispersed in thermoplastic Elium® resin using a combination of ultrasonication and shear mixing processes. This resin mix is used in a vacuum infusion process to fabricate four different intra-ply laminated composites orientations; G-0-C-90 [Carbon fibers are in the longitudinal direction], G-90-C-0 [Glass fibers are in the longitudinal direction], G-45-C-45(R) [carbon and glass fibers are at +45°, and −45° from the longitudinal direction and form a repeating layup], and G-45-C-45(A) [carbon and glass fibers are at +45°, and −45°, but with alternating directions for each lamina in the layup]. Four-circumferential probes are utilized to obtain the piezo-resistance measurements associated with damage inside the composites under shear and mode-I loadings. In the shear experimentation, the G-45-C-45(A) orientation demonstrated the largest interlaminar shear strength, at 50% greater than the G-45-C-45(R) orientation. Both G-45-C-45(A) and G-45-C-45(R) had significantly larger shear strains compared to the G-90-C-0 and G-0-C-90 orientations. However, the best resolution in shear damage sensing was seen with the G-0-C-90 composites. In the mode-I fracture experiments, the greatest fracture initiation toughness is shown with the G-0-C-90 orientation, which is 80% greater than the G-90-C-0 orientation. Compared to all orientations, the G-0-C-90 orientation also provided the most sensitive electrical response.

     
    more » « less
  4. ; ; ; ( , Polymer Composites)

    Novel conductive jute/epoxy laminated composites were fabricated by embedding carbon nanotubes (CNTs) in the matrix and flocking short carbon fibers between the laminates. A three‐dimensional electrical conductive network was generated inside the composites and the electrical resistivity values were measured using a four circumferential probe measurement system. A parametric study was performed to investigate the effect of three different weight percentages of CNTs (0%, 0.025% and 0.1%), two different carbon fiber lengths (150µm and 350µm), four different carbon fiber flock densities (500, 1000, 1500 and 2000 fibers/mm2) and two different laminates' orientations ((0‐0‐0‐0)Tand (0‐90‐0‐90)T) on the resistivity values of the composites. Composites with the lowest resistivity value of 0.019 Ohms‐m was achieved for 0.1 wt.% of CNTs and 350µm with flock density of 2000 fibers/mm2for ((0‐0‐0‐0)Tlaminate orientation. The increase in flock length from 150µm to 350µm significantly decreased the resistivity by several orders because 350µm generated better conductive network with neighbouring carbon fibers as well as with CNTs. The flock density of carbon fibers has a dominant effect on 150µm long fibers compared to 350µm when the flock density increased from 1000 fibers/mm2to 1500 fibers/mm2. Variation of both CNTs weight percentage and laminate orientation did not have significant effect on change in resistivity. The electrical measurement investigation of these novel conductive natural fiber composites will have applications in in‐situ damage sensing and structural health monitoring. POLYM. COMPOS., 40:E1189–E1198, 2019. © 2018 Society of Plastics Engineers

     
    more » « less
  5. ; ; ; ; ( , Frontiers in Soft Matter)
    Chan, Edwin P. (Ed.)

    Stress concentrations in polymer matrix composites occur due to non-uniform loadings which develop near the interface between the matrix and reinforcement in a stressed composite. Methods to better understand the evolution of this stress concentration are required for the development of advanced composites. Mechanophores, which are stress responsive molecules, can be embedded into the polymer matrix and used to quantify the local stresses in a loaded composite. In this work, single particle model composites were fabricated by combining functionalized glass particles embedded into a silicone/mechanophore matrix. Confocal microscopy was then used to measure the mechanophore activationin situduring mechanical loading. The fluorescence intensity was correlated to maximum principal stress values obtained from a finite element analysis (FEA) model of the system utilizing an Ogden hyperelastic model to represent the elastomer. By calibrating stress to fluorescence intensity spatially, quantitative stress measurements can be obtained directly from fluorescent images. To validate this technique, calibrated stress values for a two-particle composite system were compared to a FEA model and good agreement was found. Further experiments were performed on silicone matrix composites containing short cylindrical particles oriented with their major axis parallel or perpendicular to the stretching direction. To demonstrate the versatility of the single particle intensity/stress calibration approach, maximum principal stress values were mapped on the fluorescence images of the cylindrical experiments. This technique has potential to quantify stress concentrations quickly and accurately in new composite designs without the use of FEA models or differential image correlation.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email