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During the forming of aramid paper honeycomb sandwich component of aircraft composites in the autoclave, the structure bears thermo-mechanical coupling case, and it may exist the phenomenon of the honeycomb crack during the forming. The tensile, compressive, shear and thermal properties of aramid paper honeycomb core are obtained by testing. Meanwhile, the numerical simulation of thermo-mechanical sequential coupling of the whole honeycomb sandwich component and the local core area are carried out by combining the finite element analysis method and the inversion method. The results show that the thermal stress during the forming process will not cause the adhesive layer between honeycomb cells to crack, but gas pressure will. The difference value of pressure difference between honeycomb cells required for adhesive layer′s slight destruction and complete destruction is positively related to the initial normal fracture stress of adhesive layer. The pressure difference required for the adhesive layer′s complete destruction is decreased with the increase of the number of loaded cells.

Hybrid carbon fibre-reinforced (CFR) laminates have been manufactured by combining an innovative recycling process with compression moulding. Waste CFR laminates are thermo-mechanically disassembled in single thermoset (TS) plies by heating and bending in a roll-forming machine. The recovered TS layers are re-assembled by interposing a thermoplastic (TP) interlayer. In this study, waste nylon bags from composite manufacturing have been used to produce polyamide interlayers, with different nominal thickness (from 50 to 140 μm). Therefore, final hybrid laminates are 100% recycled. An extensive experimental campaign has been carried out to optimize the compression moulding process of hybrid laminates and to evaluate the effect of the TP-TS hybridization. Calorimetry, dynamic mechanical analyses, microscopy and bending tests have been performed. The optimal processing conditions were found thanks to the results from adhesion tests. In the best case, the hybrid CFR laminate showed the bending strength of 386 MPa and the bending modulus of 34.3 GPa, 47% and 54% of the virgin laminate, respectively. Moreover, the hybrid laminate has unique properties such as higher toughness, an increased damping and the ability to be thermo-formed. [ABSTRACT FROM AUTHOR]

Post-industrial trimmings and off-cuts of carbon fiber/polyether ether ketone composite were successfully recycled into new composite products. The original composites were thermally characterized by dynamic thermomechanical analysis, differential scanning calorimetry, and thermogravimetric analysis. Melt-bonding and thermoset adhesives were used to bond the carbon fiber/polyether ether ketone. Performance of the bond was evaluated through double lap-shear tests. The carbon fiber/polyether ether ketone scraps were mechanically refined to a variety of elemental sizes, subsequently subjected to high-temperature hot pressing to form panel composites. The influences of element size and processing temperature were evaluated through mechanical testing. [ABSTRACT FROM AUTHOR]

Cellular and porous polymers with internal bipolar space charge can exhibit large piezoelectric thickness coefficients and have therefore led to significant advances in the understanding and the application of piezoelectricity in polymer electrets. As possible alternatives to these cellular ferroelectrets, other potentially useful configurations of space-charge electrets, such as bi-layer or multi-layer stacks of at least one ‘soft’ porous and one ‘hard’ non-porous electret film have been suggested and investigated. Extending the concept of cellular or porous polymer electrets with microscopic voids, we propose and describe novel piezoelectret structures with regular arrays of millimeter-sized bubbles that are formed between fluoro-ethylene-propylene (Teflon®—FEP) films via a vacuum-assisted thermal process. After internal charging by means of high impulse voltages, the bubble structures exhibit rather large piezoelectric activities in their thickness direction, with phenomenological quasi-static d33 coefficients of up to 500 pC/N (or pm/V) which quite strongly decrease with the amplitude of the applied force. The electromechanical behavior of the new piezoelectrets has been modeled in analogy to the operation of electret microphones. [ABSTRACT FROM AUTHOR]

Thermo-stamping is critical for the structural application of two-dimensional (2D) woven fabric reinforced thermoplastics (WFRTPs). Reliable simulation models for thermo-stamping of 2D WFRTPs can effectively reduce the time and tooling cost caused by trial-and-error development, and thus are crucial for mature manufacturing. This article presents a survey of the literature on the characterization and simulation for thermo-stamping of WFRTPs. First, the investigations of the main deformation mechanisms of thermo-stamping and the corresponding experimental characterization methods are summarized. Then, we highlight the development of simulation models for the stamping and cooling steps, as well as the progress in the development of the continuous virtual process chain (CAE chain) for the simulations of the entire forming process and the structural performance prediction of molded parts. As the study on the stamping process becomes mature, a closed simulation optimization chain for WFRTP's thermo-stamping process has gradually been developed to reduce the overall development costs of high-performance WFRTPs. [ABSTRACT FROM AUTHOR]