OPPORTUNITY

High performance composites, such as carbon fiber reinforced polymer (CFRP), are critical materials in the aerospace, defense, wind energy, automotive, and sporting goods industries. While advancements have been made in both the fabrication processes and the final products, even modern-day CFRP laminates still lack effective structural support in the through-thickness direction (i.e. z-alignment/direction). Notably, the polymer matrix and fiber matrix interface continues to be a source of interlaminar weakness where limitations such as delamination, temperature degradation, and lightning strike protection are ever present. This interface also exhibits insufficient heat dissipation and electrical conductance, as well as difficulty in joining repairing. As CFRP composites are often manufactured into laminates, these weaknesses to the interlaminar toughness typically present in the through-thickness direction. As such, most modern design and production of CFRP parts and structural assemblies are limited by the z-direction properties. Therefore, the ability to enhance the z-directional properties will add valuable cutting-edge performance to CFRP composites and significantly advance the industry. 

BREAKTHROUGH IN NANOCOMPOSITES AND FRP COMPOSITES

Researchers at the University of South Alabama have demonstrated a transformative platform technology for manufacturing CFRPs that enhances levels in performance, mitigates weaknesses, and imparts multi-functionality to the CFRP. This technology utilizes carbon nanofibers (CNFs), while maintaining adaptability to incorporate carbon nanotubes, to thread through the FRP microfiber layers (e.g. carbon fibers, glass fibers, etc.) through thickness in the z-direction to form a superior 3-D structured composite material. These CNF “Z-Threads” in a CFRP laminate create a fiber-reinforced system that improves all z-direction properties including, but not limited to, mechanical, thermal and electrical properties. Furthermore, the CNF Z-Threads off-set the negative effects of voids in the CFRP and advance the CNF Z-Threaded CFRP’s (“ZT-CFRP”) performance and reliability over traditional CFRP. Interestingly, recent experiments and finite element modeling analysis revealed significant y-directional enhancements due to the zig-zag threading pattern of the long CNF Z-Threads passing through the carbon fiber array. The compressive strength in the x-direction (i.e., along the carbon fiber direction) was also improved significantly and can be attributed to the enhance stability support of the CNF Z-Threads on the carbon fibers. 

Our ZT-CFRP portfolio currently consists of the following: 

• Two Novel Manufacturing Processes for producing ZT-CFRP prepreg.
  1. A manufacturing process for continuous production of wide ZT-CFRP prepreg rolls; process is compatible with existing industrial standard hot-melt prepreg mass-production and manufacturing techniques for complex aerospace composite parts, sporting goods, and other high value products.
  2.  A manufacturing process described as a unique radial flow rheology-based method to fast align CNFs through the FRP fabric tape wrapping around a small roller to produce a continuous ZT-CFRP prepreg tape. This radial flow prepreg production process is very fast and affordable; its unique rheology makes it suitable for both low viscosity polymers (thermoset resins) and high viscosity polymers (thermoplastic resins). Importantly, the inventors believe this technology is particularly suitable to 3D printing in the form of a novel printing head (which is described in another invention).

Depending on the desired form factor of the ZT-CFRP prepreg, a customer may opt to employ the first method or the second method, or to interactively combine the two methods to produce the ZT-CFRP prepregs.  

• A novel porous ZT-CFRP composite material enabled by the ZT-CFRP prepreg production. The cured porous ZT-CFRP laminate contains approximately 70% carbon fibers and 1% of CNF Z-Threads with about 15% resin and 14% porosity. The composite’s weight is effectively reduced by approximately 12% while maintaining comparable or better strengths than traditional CFRP laminates lacking voids. Such improvements are due to the well-connected network formed by the zig-zag CNF Z-Threads and the carbon fibers. This composite product has tested at 100 to 300 times more electrically conductive in the z-direction than traditional CFRP laminates.  The porosity can be used to improve acoustic control and impact absorption; and, it can be filled with other functional materials or coatings to further enhance the material’s multi-functional performance without major concern that the end product will be any heavier than traditional CFRP products.

COMPETITIVE ADVANTAGES

• Suitable to continuous production of carbon nanofibers z-threaded FRP prepreg with large width
• Enhanced strength to weight ratio
• Enhanced electrical and thermal conductivities
• Enhanced matrix-sensitive mechanical properties, e.g., delamination resistance, shear strength, compressive strength, mitigation of stress concentration
• Better curing repeatability than traditional CFRP prepreg
• Cost-effective continuous volume production
• Compatible with traditional CFRP prepreg manufacturing process
• Comprehensive enhancement in all directions, i.e., x, y, and z directions of a CFRP laminate. 
• Very small quantity of CNF required, i.e., 1 wt%-2 wt% in the polymer matrix
• Compatible with nano-enhanced adhesives for adhesive-joining CFRP composite parts
• Versatile functions for novel applications and CFRP products

INTELLECTUAL PROPERTY STATUS

First Prepreg Manufacturing Method (compatible with Hot Melt Prepreg Process): Granted Patents: US10066065B2, CN105517781B, Pending Patent Applications: JP2016527365A, EP3027390A4, WO2015017321A1. 

Second Prepreg Method (radial flow method): Granted Patents: JP6462115B2, Pending Patent Applications: US20170182718A1, EP3148711A4, CN106660068A, WO2015184151A1

Porous CNF Z-Threaded CFRP: Patent Pending: WO2016036663A1, US20170240715A1, CN106795656A, JP2017528611A, EP3189178A4