The Role of Stitch Yarn on the Delamination Resistance in Non-crimp Fabric: Chemical and Physical Interpretation

Abstract

Low-bandgap organic polymers, poly[(4,4 bis(2 ethylhexyl)cyclopenta [2,1 b:3,4 b′]dithiophene) 2,6 diyl al (2,1,3 benzothiadiazole) 4,7 diyl](PCPDTBT), and poly [(4,4′ dioctyldithieno[3,2 b:2′,3′d] silol 2,6 diyl) alt (2,1,3 benzothiadiazole) 4,7 diyl)], (Si-PCPDTBT) were analyzed at the air-water interface forming a Langmuir monolayer. In order to form stable monolayers and to transfer to solid supports, amphiphilic molecules of stearic acid (SA) were mixed with them. For the pristine polymers, the floating monolayers were transferred onto solid substrates via the Langmuir-Schaefer (LS) technique. Surface pressure-area isotherms and compressibility modulus curves demonstrated that the SA incorporation to the polymers at the air-water interface modified the rheological properties of the Langmuir films, since the films became less compressible at higher pressures and there is clear conformational reorganization taking place at intermediary pressures. The UV-Vis absorption also depicted the changes on the overall film morphology by the shift on the maximum absorption bands, and along with cyclic voltammetry curves the absorption spectra made it possible to estimate the energy diagrams for the polymers. Photoconductivity effects were observed for all the sample, among which the pristine polymers fabricated by LS showed better results, suggesting that the organization provided by the Langmuir-Blodgett (LB) technique was not enough to overcome the insulating characteristic of the SA molecules in this specific configuration.

Interlaminar crack onset in co‐cured and co‐bonded composite joints under mode I cyclic loading

“…This continues until the elastic energy diminishes and achieves the equilibrium condition, as the energy failure for the surface of the adhesive is less than the first load. Detail A in Figure illustrates the initial rough aspect through the adhesive, which reflects the unstable nature of delamination propagation, which is in accordance to the observation of Shiino and Amaral …”

“…During the quasi‐static delamination propagation, the crack migrated from the adhesive layer to the neighboring prepreg layer revealing the difference in the toughness, as seen in Figure A, as the texture in the adhesive is rougher than the prepreg, at which presented smooth surface. These observations are in accordance with Amaral et al and Shiino et al, who related the rough aspect to the increase of SERR. Figure B of the CC joint fracture surface showed the same texture as identified in the crack migration as shown in detail of Figure A.…”

“…Detail A (Figure ) is a consequence of the driving mechanisms, that could be separated and counted as depicted in detail A. The procedure for separating the fracture patterns is available in Shiino et al, which segregated patterns resulted in 18.14% of the area covered by these fracture patterns.…”

Recent Industrial Developments of Marine Composites Limit States and Design Approaches on Strength

“…On the other hand, noncrimp fibers are more expensive than traditional woven roving, thus their application is limited to highperformance composites. Another critical aspect was highlighted by Shiino et al (2017) in delamination problems, which found a decrease in the surface propagation energy because the stitch yarn replaced the carbon fiber/ epoxy interface, which has better chemical affinities.…”

Multiscale Polymer Composites: A Review of the Interlaminar Fracture Toughness Improvement

“…There are several manufacturing techniques available for making reinforcement preforms for composite laminates and these include (1) Braiding [80,81], (2) Stitching [82][83][84][85][86][87][88], (3) 3D Z-Pinning [89][90][91], and (4) 3D weaving [92]. The schematic of different types of 3D sandwich structure is depicted in Figure 5.…”