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A comparative study is presented on the fracture toughness of carbon fiber/PEEK composites manufactured by autoclave and laser-assisted automated tape placement (LATP). Formation of a good inter-laminar bond is always a concern in ATP due to the short time available for intimate contact development and polymer healing, yet our double cantilever beam (DCB) tests reveal 60-80% higher Mode I fracture toughness for the LATP processed specimens than for the autoclave processed specimens. This magnitude of difference was unexpected, so specimens were further examined via differential scanning calorimetry, dynamic mechanical analysis, nano-indentation, and scanning electron microscopy. The results indicate that the LATP process has been very effective in heating and consolidating the surface of plies, creating an excellent bond. However, it has been less effective in processing the interior of plies, where a low crystallinity and poor fiber-matrix bonding are evident. The higher fracture toughness of the LATP processed specimens is also not solely due to a better bond, but is partially due to significant plastic deformation in the interior of plies during the DCB test. The findings indicate there is still considerable scope for optimizing the laser-assisted ATP process, before the optimum balance between strength and toughness is achieved at favorable lay-down speeds.

This work documents the development of the title system wherein the first dimension is a separation of polyolefins, according to composition, via an adsorption mechanism on a HYPERCARB stationary phase, and the second dimension is a separation of polyolefins on a gel permeation chromatography (GPC) column. Proper optimization of the experimental parameters including high temperature liquid chromatography (HTLC) flow rate, GPC flow rate, GPC column type, and solvent gradient program enabled successful operation of the two-dimensional (2D) system. Two angle light scattering at 90°and 15°and solution infrared absorbance detectors were used for qualitative and quantitative analysis of the 2D data. Apparent composition distribution, apparent molecular weight distribution, and the complete twodimensional (composition  molecular weight) distribution were obtained for a given polymer. This system is an improvement over a prior two-dimensional system based on temperature rising elution fractionation (TREF)/GPC in that TREF has difficulty separating polyolefins by composition if the polyolefins contain more than approximately 8 mol percent comonomer. Polyolefins synthesized from different catalysts (Metallocene and Ziegler-Natta) showed differences in the molecular weight, composition and number of resolved species in their respective 2D HTLC-GPC chromatograms as a function of catalyst type. Although the polymers studied here were all polyolefins, this approach can also be extended to other polymers.

Anionic and nitroxide-mediated (NM) radical polymerization works well for styrene but not for acrylates. We have overcome this problem and successfully prepared styrene-b-n-butyl acrylate (S-BA), styrene-b-methyl methacrylate (S-MMA), styrene-b-isoprene (S-IP), and styrene-alt-acrylonitrile-b-isoprene (SAN-IP) polymers using a sequential normal/living radical polymerization scheme. Clear (S-IP and SAN-IP) to translucent (S-BA and S-MMA) films were obtained having microphase-separated polymer morphology. GPC studies and chemical digestion of the IP segments of S-IP and SAN-IP block copolymers confirmed their block structure. The sequential normal/living radical polymerization approach provides a new route to synthesize block polymers that have previously proven very difficult to make.