Ochre (Oc), with its high absorption and viscous properties and presence of several inorganic components, was incorporated in a polycarbonate‐unmodified carbon nanotubes using processing methods such as electrospinning and compression molding, to produce strong and flame resistant composites with biaxially oriented nanomaterials. These composites were found to have good mechanical properties (ultimate tensile strength of ∼95.3 MPa) and flame resistance (∼464 J g−1K−1 heat release capacity) when ∼1 wt% of single‐walled carbon nanotubes was used with 2.5 wt% Oc, which was used as a compatibilizer and flame retardant. POLYM. ENG. SCI., 54:1289–1299, 2014. © 2013 Society of Plastics Engineers

Damage in cryogenic composite fuel tanks induced during manufacturing and advanced by thermomechanical cycling can accelerate leakage of the propellant. Whether the leakage exceeds tolerable levels depends on many factors, including pressure gradients, microcrack density, other damage such as delamination, connectivity of the cracks, residual stresses from manufacture, service-induced stresses from thermal and mechanical loads, and composite lay-up. This article is concerned with the creation and the detection of damage in cryogenic composites due to thermomechanical loading. The first part deals with cryocycling (cycling between two temperatures) test procedures, that were developed to understand the damage produced in cryogenic composite laminates under thermomechanical loading. An apparatus was developed to thermomechanically cycle coupon test specimens under different thermomechanical loadings. IM7/977-2 and IM7/5250-4 graphite/epoxy cross-ply [90 2 /0 2 ] S and angle-ply [0/-45/ 90/45/0/45090/-45/0] S laminates were tested using these systems. Ply-by-ply microcrack density was measured as a function of thermomechanical cycles. The second part of this article deals with effect of thermal gradients due to sudden exposure to a cryogenic temperature. The sudden exposure to cryogenic temperatures may have caused the microcracks, due to large temperature variations through the thickness and the resulting thermal stresses. In this work, an investigation of the sudden exposure to cryogenic temperatures is conducted experimentally with and without an insulating layer. POLYM. COMPOS., 34:607-615, 2013. ª 2013 Society of Plastics Engineers FIG. 4. Micro-crack density versus number of cycles for the [-45] ply (second from outer surface) of IM7/ 977-2 laminates with [0/-45/90/45/0/-45/90/45/0] S under uniaxial tension loading. FIG. 5. Micro-crack density versus number of cycles for the [90] ply of IM7/5250-4 laminates with [90 2 / 0 2 ] S under four-point bending.

The structural weight of a cryogenic propellant tank for reusable launch vehicles (RLVs) can be effectively reduced by the use of advanced composite materials. However, microscopic damage such as transverse matrix cracks (TMC) and delaminations are prone to develop in composites well below the load levels that would result in mechanical failure. This microscopic damage leads to a leakage path for the fuel. The leakage is influenced by many factors including connectivity of the cracks, residual and service-induced stresses, and composite stacking sequence. This article is concerned with the effect of thermal gradients due to sudden exposure to a cryogenic temperature with and without insulation layer. An investigation of the insulation layer for sudden exposure to cryogenic temperatures is conducted numerically. The exposure of the harsh environment could make the damages such as delaminations, TMC, and leakage path. The defects from manufacturing could be formed, and they are critical parts under sudden exposure to cryogenic temperature. Therefore, the qualitative analysis for insulation technique is needed. The results from this article are very important because the stress levels which cause damages can be predicted and also controlled using the insulating techniques. The insulation skill which can suppress the stress levels is newly introduced in this article for RLV cryogenic fuel tank. Moreover, the effect of lay-ups is also investigated in this article. The thermal gradient can be controlled by using different lay-ups. POLYM. COMPOS., 34:531-536, 2013.