Solid carbon fiber/epoxy laminates manufactured by liquid resin infusion of twill fabric reinforcement are recycled in a bath of boiling sulfuric acid to separate the fibers from the matrix. The recycled reinforcement consists of long fibers arranged in a random, entangled mat. Using the same epoxy matrix and infusion materials and process, the recycled fibers are reutilized to manufacture solid laminates. The physical properties of the recycled laminates are evaluated by means of pulse-echo ultrasound, visual microscopy, and fiber volume content. The average fiber volume content of the recycled laminates is 33%, compared to the 62% of the twill laminates. The mechanical properties of the recycled composite include tension modulus and strength, compression modulus and strength, three-point bend flexure strength, and short beam shear strength. The properties are compared against the values of the twill reinforcement with quasi-isotropic stacking sequence. Results show that the recycled material offers promising elastic properties and strength values, similar to those of advanced carbon fiber sheet molding compounds, and therefore can be used as structural material.

The limits of processability of solid-state thin film lithium-ion batteries embedded into composite laminates are identified through testing under pressure, temperature and a liquid resin environment representative of composite processing cycles. Battery failures are characterized based on optical microscopy and capacity retention, and three distinct types of failures are recognized and analyzed. Failures are associated either with the battery polymeric sealant failure or with the physiochemical degradation of the electrolyte or the anode. Results give evidence that the cure temperature is the most influential parameter for battery survivability. Based on these experimental results, the optimum curing cycle is identified and embedding tests that retain full battery capacity are successfully performed. The minimal three-layer battery packaging proves to be an efficient air and moisture barrier within the above conditions.

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