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Spread tow carbon fiber composites are receiving increased attention for diverse applications in space and sports gear due to their thin form, which is suitable for deployable structures, and high tensile strength. Their compressive strength, however, is much lower than their tensile strength due to low interlaminar strength. Herein we report a facile technique to enhance their performance through interlaminar insertion of aligned carbon nanotube (CNT) sheets. The inserted CNT sheets also provide electrical conductivity in the composites even at a low CNT loading below the electrical percolation threshold established for CNT-filled composites. Mechanical and electrical characterization was conducted on the CNT sheet-inserted composites and the baseline composites. Results show that the CNT sheets increase the compressive strength by 14.7% compared with the baseline. Such an increase is attributed to the increased adhesion provided by the inserted CNT sheets at the interface between neighboring plies, which also increases the interlaminar shear strength by 33.0% and the interfacial mode-II fracture toughness by 34.6% compared with the baseline composites without inserting CNT sheets. The well-aligned CNT sheet structure maintained between the neighboring plies contributed to a 64.7% increase in electrical conductivity compared with the baseline composites. The findings indicate that the insertion of well-aligned ultrathin CNT sheets in the interlaminar region of a spread tow carbon fiber composite provides significant enhancement in mechanical and electrical performance, paving the path toward applications where both mechanical and electrical performances are crucial, such as for structural health monitoring, lightning protection, and de-icing in aircraft and wind blades. 

Seismic attenuation is an important parameter for characterizing subsurface morphology and thermal structure. In this study, we useP‐wave amplitude spectra from 588 teleseismic events recorded by 477 broadband seismic stations in the southeastern United States to examine the spatial variations of seismic attenuation in the crust and upper mantle. The resulting seismic attenuation parameter (∆t*) measurements obtained using the spectral ratio technique reveal a zone of relatively low attenuation in the Gulf of Mexico Coastal Plain and the southwestern terminus of the Piedmont province. Spatial coherency analysis of the ∆t* observations suggests that the center of the low attenuation layer is located within the uppermost mantle at about 70 km depth. This low attenuation anomaly lies along the suture zone between Laurentia and Gondwana and approximately coincides with the east‐west trending Brunswick magnetic anomaly. The origin of this low attenuation anomaly can be attributed to low attenuation bodies in the form of remnant lithospheric fragments in the deep crust and the uppermost mantle. The contribution of scattering to the observed ∆t* is estimated by calculating the ratio of amplitude on the transverse and vertical components in theP‐wave window. Relative to the rest of the study area, the Gulf of Mexico Coastal Plain demonstrates weaker scattering which is suggestive of a more homogenous crustal and uppermost mantle structure.