Polymers

Thermoplastic carbon fiber-reinforced polymer (CFRP) composites possess the intrinsic capability to heal delamination and matrix cracks via thermal re-melting. However, under impact loading, they are prone to severe fiber fracture, which significantly compromises their repairability. To address this, this study introduced polytetrafluoroethylene (PTFE) films as pre-set interlaminar defects within continuous carbon fiber-reinforced polyamide 6 (CF/PA6) thermoplastic cross-ply laminates. Low-velocity impact tests were conducted at varying energy levels to comparatively investigate the impact response and damage mechanisms of the CFRPs with and without embedded defects. Experimental results indicate that the embedded interlaminar defects triggered a transition in the failure mode of the CFRP from brittle fracture to progressive damage behavior. Compared to the baseline laminates, the specimens with embedded defects maintained higher flexural stiffness under low-energy impact. Furthermore, they effectively reduced the extent of fiber breakage by dissipating impact kinetic energy through extensive delamination, interlaminar frictional sliding, and plastic micro-deformation. These findings verify the feasibility of achieving macroscopic pseudo-ductility through interlaminar microstructural tailoring. This research provides an experimental basis and methodological support for the pseudo-ductile design of thermoplastic composites.

Buprenorphine (BUP) is widely used in the treatment of neonatal opioid withdrawal syndrome (NOWS). However, the most compounded formulation contains 30% ethanol, despite regulatory and clinical concerns regarding ethanol exposure in pediatric patients. Thus, this research aimed to develop an ethanol-free sublingual (SL) gel formulation of BUP that would be safe, stable, and suitable for NOWS. Multiple polymers were screened as gelling agents, with hydroxypropyl methylcellulose (HPMC) emerging as the ideal base polymer for the formulation due to its optimal pH, rheological characteristics, and stability. The formulated gels were stored at room temperature and refrigerated conditions for 30 days and evaluated for stability using pH, rheology, and liquid chromatography-mass spectrometry. BUP content was between 90–110% of the labeled amount of the dosage form (75 µg/mL) at all time-points, and the pH remained close to physiological values. Release studies demonstrated a drug release of 23–24% for SL gels without surfactants stored at room temperature and refrigerated conditions, respectively. Incorporation of non-ionic surfactants (Tween 20 and Tween 80) significantly increased drug release to 33% and 40%, respectively, reflecting enhanced solubilization and improved mucosal penetration. The ethanol-free formulation demonstrated physicochemical stability and favorable release characteristics suitable for neonatal administration. These findings represent a meaningful advance in the development of safer pediatric formulations for NOWS.

Fiber-reinforced composites are extensively utilized in mass-critical structures spanning aerospace, automotive, civil, etc., owing to their exceptional specific strength and stiffness. Fiber volume fraction (FVF) is a critical parameter for evaluating the performance of the composites. As a consequence, different measurement methods have been developed in recent decades, including resin removal method, thickness measurement method, microscopic method, etc. This paper reviews both traditional destructive (acid digestion, combustion, image analysis, etc.) and newly developed non-destructive techniques (X-ray CT, thermography, ultrasonic, XRD, eddy current, etc.), with a focus on their applicability to specific materials, measurement accuracy, operational complexity and cost. Moreover, key challenges and future directions are discussed, emphasizing the need for non-destructive testing, cost and energy efficiency, intelligent measurement and sustainability.