Thermal expansion, specific heat, diffusivity, and conductivity of carbon fiber-epoxy composites were studied using autoclave and out-of-autoclave prepregs with three different fabric weaves including unidirectional, eight-harness satin, and plain weave. For this purpose, light flash analysis was utilized where the implications of using anisotropic materials were studied. Results indicated that density, thermal expansion, conductivity, and diffusivity were strongly influenced by the fiber configuration of the sample. This phenomenon was attributed to the difference in fiber volume fraction induced by the different weaves of the fabric. Nevertheless, specific heat was similar for all the samples regardless of fabric type or resin formulation. Finally, thermal properties of tetrafluoroethylene release film were presented to analyze the tool-part heat transfer during manufacturing. This release film showed thermal conductivity three times lower than carbon fiber-epoxy samples indicating that the film could be an important contributor to thermal lag between tool and part.

To predict the final geometry of carbon fiber-epoxy composite parts, a methodology is introduced that takes into account cure kinetics, cure shrinkage, thermal strains, tool-part interface, and development of mechanical properties during cure. These parameters affect process-induced residual stresses and distortion in the parts. A module was developed for each mechanism and a fully 3D coupled thermomechanical finite element analysis was utilized. To validate the simulation results, a square composite panel was fabricated and its pattern of distortion was obtained. The simulated distortion pattern agreed well with the actual pattern obtained from the experiments. Parallel processing and optimization of the developed codes were used resulting in 94% reduction in the computational time. The proposed methodology proved to be accurate and time-efficient in predicting the final geometry of the parts. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 941-950, 2013

An active thermoplastic film made of low-density polyethylene (LDPE) filled with oxygen scavengers made of powdered activated carbon (PAC) impregnated with sodium erythorbate (SE) was developed for packaging applications. Initial tests indicated that the impregnation of PAC with SE enhanced the heat resistance of SE, thereby allowing processing at temperatures typical of LDPE manufacturing. Subsequently, LDPE films with PAC/SE particles were manufactured in coupons that represented a typical juice package, and experiments indicated that these films absorbed 3.57 mg of oxygen in 11 days. This amount corresponded to 80% the concentration of oxygen in the headspace of the package. Furthermore, findings indicated that active particles alone have 10 times higher oxygen absorption capacity than the active LDPE film. Finally, the physical properties of the film were characterized by microscopy where oxygen scavengers showed a good dispersion within the matrix. However, 20 wt.% of these active particles decreased tensile strength of the film by 53%.

In this article, shear stress between an aluminum tool and a carbon fiber-epoxy prepreg is characterized during cure using polymeric release agent and release film at the tool-part interface. The effects of surface roughness, release materials, pull-out speed, temperature, and normal force (autoclave pressure) on the shear stress are investigated using a customized friction rig. Results show that the interfacial shear stress decreases as the temperature increases and it increases as the normal force increases when using either the release film or the release agent. Additionally, changes in surface roughness from 1.35 to 0.18 lm decrease the shear stress 10-27% while the use of release agent shows a decrease between 23% and 51% in the shear stress. Furthermore, strong adhesion between the tool and the part is observed when using release agent and pull-out speeds of 0.05 mm/min (static/dynamic friction ratio of 5.29 6 0.19). Using the experimental data, a mathematical approach based on the Coulomb's friction model is proposed to predict the friction force at the tool-part interface.

In this study, flat composite panels were fabricated to find the effect of different manufacturing parameters, including stacking sequence, part thickness, and tooling material, on distortion of carbon fiber‐epoxy composite parts. L‐shaped and U‐shaped panels were also made to investigate the effect of stacking sequence on spring‐in angle and warpage of the curved panels. Results showed that distortion of the flat panels caused by asymmetry in the stacking sequence was an order of magnitude greater than distortion of the panels with an unbalanced stacking sequence; whereas in the curved panels, the panel with an asymmetric stacking sequence showed the least spring‐in angle, and the largest angle was observed in the symmetric panel. MSC Marc was used to predict distortion of the panels, and the simulation results were compared with the experimental results for several stacking sequences of the flat and the L‐shaped panels. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40439.