Ricardo De Medeiros

Driven by the demand for lightweight and efficient structures, composite materials are increasingly used in the automotive, aeronautical, and aerospace sectors due to their high stiffness-to-weight and strength-to-weight ratios. In addition to improving structural performance and reducing fuel consumption, composites enable the integration of embedded sensors for smart structures capable of self-monitoring and adaptive control. Conventional piezoelectric sensors, such as lead zirconate titanate (PZT) and Macro Fibre Composites (MFCs), provide excellent electromechanical performance but are relatively stiff, expensive, and difficult to integrate into lightweight structures. Although thermoformed electrets have emerged as a promising polymeric sensing technology, their applicability to vibration-based damage detection remains insufficiently explored. This study evaluates the feasibility of a thermoformed fluorinated ethylene propylene (FEP) electret as a polymeric piezoelectric sensor for damage detection in a thermoplastic carbon fibre composite beam. Experimental modal analyses under free and forced vibration were performed using impact hammer and shaker excitation. The electret response was compared with measurements obtained from an accelerometer and an MFC sensor. A finite element model was validated against experimental intact and added-mass configurations and subsequently extended to investigate numerical damage scenarios, including delamination and through-thickness cracks. The calibrated model predicted the experimental natural frequencies with errors below 7%. The first natural frequency decreased from approximately 81 Hz in the intact beam to 61.8 Hz after the addition of a 15 g mass. The thermoformed electret successfully identified the first two bending modes and detected progressive structural changes through variations in the frequency response functions (FRFs). Although its damage indices were lower than those obtained with the accelerometer and MFC sensor, particularly for low and moderate damage levels, the electret effectively monitored structural changes while offering advantages such as low weight, flexibility, ease of integration, and low cost.

Carbon nanostructures deposited on natural fibre surfaces can modify the fibre–matrix interface and influence load-transfer behaviour in polymer composites. In this study, carbon nanotubes were deposited onto jute fibre surfaces using a high-impulse electrophoretic deposition process. Epoxy-based composites with a fibre volume fraction of 45% were manufactured by vacuum-assisted resin transfer moulding using untreated jute fibre (JFEC) and carbon nanotube-coated jute fibre (CNT/JFEC). The interfacial behaviour of the composites was investigated using single yarn pull-out, short beam shear, transverse tensile, and dynamic mechanical analysis tests. The pull-out results revealed comparable interfacial shear strength values for treated and untreated fibres, indicating no statistically significant increase in IFSS. However, scanning electron microscopy showed a shift in the failure mechanism from fibre pull-out to increased fibre breakage in CNT-coated samples, suggesting a modification in the load-transfer behaviour at the fibre–matrix interface. Mechanical testing revealed a 17% increase in transverse tensile strength and a 10% increase in short beam shear strength for CNT/JFEC composites. In addition, dynamic mechanical analysis showed a notable increase in storage modulus in both the glassy and rubbery regions. These results indicate that the CNT coating alters the interfacial region and promotes more efficient stress transfer within the composite system.

Lightweight and high‐strength materials are important in robotics, as structural design impacts efficiency, payload capacity, and energy consumption. Composite materials, with their superior stiffness‐to‐weight ratios and multifunctional properties, offer clear advantages over conventional metals and polymers. This review critically examines the use of composites in robotics, with a focus on their structural, active, and sensory functions. A systematic literature review based on an adapted PRISMA framework identified over 100 publications from 1988 to 2026, revealing continuous research growth and rising interest in soft robotics, piezoelectric composites, and carbon‐based structures. In contrast, bioinspired systems have declined due to integration and manufacturing challenges. Despite the progress, major barriers remain, particularly scalability, long‐term reliability, and cost. This work proposes a functional taxonomy of composites in robotics and outlines future directions, including sustainable bio‐based materials, multimaterial additive manufacturing, and 4D‐printed adaptive systems. By integrating materials science and robotics, this review provides a concise roadmap, in composite structures, for developing high‐performance, multifunctional, and sustainable robotic technologies.

Natural‐fiber composites have gained attention as sustainable alternatives to synthetic‐fiber materials. However, their performance is still limited by fiber‐matrix adhesion, moisture sensitivity, and variability in mechanical properties. In this study, bio‐based polyurethane (PU) composites reinforced with woven jute and flax fabrics were manufactured using a vacuum‐assisted resin transfer molding (VARTM) process. The materials were characterized through density measurements, Fourier‐transform infrared spectroscopy (FTIR), X ‐ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and mechanical testing. Mechanical characterization was performed through tensile tests (ASTM D3039, ASTM D3518), where Digital Image Correlation (DIC) was employed to calculate elastic properties (, , , and ). Additional analyses included flexural testing (ASTM D790). Flax‐reinforced composites exhibited the highest tensile and flexural performance, while jute‐reinforced composites showed superior thermal stability. SEM analyses revealed interfacial voids and incomplete fiber wetting, consistent with the observed mechanical behavior. These findings demonstrate the feasibility of using castor oil–based PU with natural fiber reinforcements for eco‐friendly structural applications.

Laminated piezoelectric composites are widely used as smart materials due to their outstanding performance in sensing, actuating, and energy harvesting, especially in the aerospace, automotive, and medical industries. However, their structural integrity and reliability are often compromised by delamination. This research investigates the combined influence of delamination and interphase degradation on laminated piezoelectric composites. Using a multidisciplinary strategy that integrates analytical techniques with numerical simulations, the present investigation simulates the mechanisms responsible for accelerated delamination under interphase degradation. A two-scale asymptotic homogenization method (AHM) is employed to determine the effective piezo-electromechanical properties, while finite element analysis (FEA) with periodic boundary conditions provide accurate and realistic simulation results. Results show that progressive interphase degradation can reduce the effective stiffness by up to two orders of magnitude and substantially decrease the piezoelectric coupling, while the dielectric response remains nearly constant. These findings emphasize the crucial role of the interphase in the electromechanical behavior of smart composites and its incorporation into Structural Health Monitoring (SHM) frameworks for enhanced reliability and predictive accuracy.