This study investigates the quasi-static and viscoelastic properties of additively manufactured (AM) PETG reinforced with short carbon fibres. Samples were manufactured using different parameters in terms of the infill pattern, porosity, and annealing condition. Tensile and compressive tests were conducted to determine quasi-static properties such as Young’s modulus and toughness, and dynamic mechanical analysis was used under a frequency sweep of 1–100 Hz to describe the viscoelastic behaviour of the composites. The major impacts and responses between the print parameters were quantified using Analyses of Variance (ANOVAs), which revealed the major contributor to each mechanical property. Fractography on the tensile samples using scanning electron microscopy demonstrated fibre pull-out, indicating poor fibre–matrix bonding, but also revealed interfacial bonding between raster lines in the annealed samples. This had a prominent effect on the properties of latitudinal samples where the force applied was perpendicular to the raster lines. Generally, porosity appeared to have the greatest contribution to the variance in the mechanical properties, with the exception of the tensile modulus, where the infill pattern had a more substantial effect. Annealing caused a consistent increase in the tensile modulus of the tested samples, which can be used to support the design and optimisation of AM parts when they are used under specific loading conditions.

Comprehensive analysis of the anisotropic nature of additively manufactured (AM) parts caused by their fabrication method requires attention, as current quasi-static experiments on AM specimens are used to determine strength and stiffness. This study investigates the anisotropic mechanical behaviour of AM polymer composites reinforced with short and continuous carbon fibres, examining various filament orientations, loading directions and strain rates. Utilising the fused deposition modelling (FDM) technique, nylon and carbon fibres were fabricated into composites with controlled orientations. Mechanical tests were conducted in different directions to assess the tensile and compressive properties of these composites, with results showing enhanced tensile strength and stiffness in continuous-fibre (CF) composites compared to short-fibre (SF) ones, particularly in longitudinal orientations. The compressive behaviour revealed complex effects of type and orientation of reinforcing fibres, with CF composites demonstrating superior stiffness but lower strength than SF composites in specific orientations. Strain rate sensitivity analysis for the least anisotropic (quasi-isotropic) cases indicated that tensile strength decreased slightly with the increased strain rate while compressive strength increased. These findings underline the critical effect of fibre orientation and type on mechanical properties and suggest potential applications of AM composites in scenarios demanding tailored anisotropic behaviours, including structural optimisation and numerical modelling for various loading conditions.

Katydids (Insecta, Orthoptera, Tettigoniidae) possess a sophisticated foreleg ear with two tympana receiving sound externally through a pinna that acts as a bat detector and internally through an acoustic trachea for conspecific communication. Their miniature scale hinders experimentation, prompting the use of scaled models, yet previous studies have not replicated the full pinna–tympana assembly or the complete acoustic trachea. In this study, micro-CT imaging, AI-assisted segmentation and multi-material 3D-printed assembly were used to generate scaled models. Scaled copies of the pinna-tympanum assembly and the complete acoustic trachea of the neotropical katydid Copiphora gorgonensis were fabricated from high-fidelity reconstructions. Flexible TPU membranes reproduced the expected pressure-driven vibration pattern at the scaled frequency, and when paired with rigid PLA pinnae, they captured the overall outer-ear acoustic response, producing ultrasonic gain within 70–110 kHz that is consistent with the in vivo bat-detection band. Separately, the pressure mapping of the scaled acoustic trachea confirms the spiracle as a filter and the exponential canal as a 17–21 dB amplifier, in line with simulations, consistent with the 1.3-cycle phase shift observed at 23 kHz in living insects. These matching results support the use of scaled biomimetic replicas as reusable, 3Rs-aligned partial substitutes and complements to live-insect acoustic studies in search of bio-inspired applications. Taken together, these outcomes provide a basis for translating the underlying acoustic and structural principles into future miniature engineering systems, including bio-inspired MEMS microphones and compact directional sensors, where passive amplification and filtering remain desirable for improving energy efficiency and signal clarity.

Miniature dual-input hearing in katydids underpins communication and bat evasion, yet its microscale anatomy hinders acoustic studies. With µCT imaging, AI-assisted segmentation and multi-material 3D printed assembly, scaled copies of high-fidelity pinna-tympanum assembly and a complete acoustic trachea of the neotropical katydid Copiphora gorgonensis were fabricated. Flexible TPU membranes reproduce similar tympanal vibrations compared to actual insect and pairing with rigid PLA pinnae mimicked the outer-ear motion, providing ultrasonic gain at 70–110 kHz matching in vivo bat-detection bands. Separately, the pressure mapping of the scaled acoustic trachea confirms the spiracle as a spectral filter and the exponential canal as a 17–21 dB amplifier, in line with simulations, preserving the 1.3 cycle phase shift seen at 23 kHz in living insects. These matching results justify the use of scaled biomimicking replicas as reusable, 3Rs-aligned substitutes for living insect acoustic studies in search bioinspired applications.