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Current integrated thermal protection systems (ITPS) are generally devised with single layer metal sandwich panel and uniform insulation material, inevitably leading to limited thermal insulation effect and high risk of buckling failure. By contrast, here, ITPS, which incorporates graded insulation materials and multilayer ceramic matrix composite cellular sandwich panels, is devised to raise both thermal insulation effect and buckling strength. The effective thermal and mechanical properties are theoretically established. Transient heat transfer characteristics are numerically calculated. The results reveal that ITPS with specific graded insulation materials can present lower temperature and better temperature distribution uniformity than those of ITPS filled with uniform insulation material, demonstrating that graded insulation layers can firmly enhance the insulation effect. Besides, the insulation effect of ITPS, in which the densities and thermal conductivities of graded layers are taken arranged from low to high, is much better than those of ITPS which have opposite sequence. Moreover, the buckling strength is demonstrated to be significantly improved through the approach of integrating multilayer sandwich panels. The thermal short effect can be also suppressed, since it is demonstrated that the multilayer sandwich panels in the ITPS can reduce the temperature on bottom facesheet and raise the temperature distribution uniformity.

Additive manufacturing technology has been increasingly applied to fabricate continuous fiber reinforced thermoplastic composites for its potential in fabricating complex structures. Owing to the limited thermal and mechanical properties of the matrix, it is a critical trend to develop high-performance thermoplastics to widen engineering applications. This study aims to comprehensively investigate the properties of the prepared CCF/PEEK filaments together with their printed composites. The filaments were fabricated via a thermo-mechanical coupling process and were characterized by micromorphology observation, thermal and mechanical test. It was found that the impregnation behavior, thermal stability and mechanical performance of the filaments were improved with the increase of mold temperature and decrease of traction speed. The performance of printed specimens was evaluated by mechanical test and fracture analysis. It was concluded that the additive manufacturing process promoted the secondary impregnation behavior of the filaments. Higher nozzle temperature and bed temperature together with lower layer thickness and printing speed enhanced the tensile strength of printed specimens with maximum value reached 509.56 MPa. Besides, the analysis of failure mechanism indicated that filament fracture, horizontal cracks and filament pullout together with fiber breakage, fiber pullout, unimpregnated fibers and pores were the dominant failure modes for all printed specimens.

Tailoring thermal expansion of structures is in urgent need in engineering applications where the structures are susceptible to suffer large temperature fluctuation. Here, a method to reconstruct 3D truss structures is developed to obtain large positive, zero and even negative coefficient of thermal expansion (CTE). As the basis, theoretical analysis and numerical verification of the bi-material pyramid and tetrahedron lattice cells explicitly reveal that with thick members, the influence of the cross section on the CTEs should be well considered, and the CTEs should be accurately calculated by the solid model. Furthermore, two kinds of 3D lattice structures with isotropic tailorable CTEs are originally devised. Moreover, bi-pyramid and bi-tetrahedron units are devised, and a reconstruction method, which can reconstruct an arbitrary 3D truss structures to obtain specific target CTE, is originally developed. Typical supporting structure and platform used in satellites are reconstructed by the proposed method, and near zero thermal expansion, which is urgent needed in satellite, can be flexibly obtained. The analysis and proposal of three dimensional lattice structures and reconstruction method provide a new approach to develop structures with light weight and tailorable CTEs.

The engineering materials and structures, which usually suffer both temperature variation and mechanical loading, motivate the urgent need of the multifunctional metamaterials with simultaneously programmable coefficient of thermal expansion (CTE) and Poisson’s ratio (PR). Whereas, the current 3D metamaterials can not continuously program the CTE and PR. Herein, a class of 3D metamaterial is originally devised by an exclusive geometrical methodology. The explicit expressions of the CTE and PR are theoretically established and are also verified by the numerical modeling. The analysis confirms that the CTE can be widely tailored by varying the geometrical parameters and selection of the constituents. Besides, the controllable PR can be also easily obtained by adjusting the geometrical parameters. Moreover, the devised 3D metamaterial gives paired tailorable CTE and controllable PR, including especially negative CTE + negative PR. An arrangement rule is developed to construct a series of hierarchical cells which can program CTE and PR in multi principle axes and can be periodically arrayed for obtaining the 3D cellular metamaterials. The devised 3D metamaterials are capable of realizing the widely coupled programmability of both CTE and PR and provide a strategy of shape morphing stimulated both by temperature variation and mechanical loading.

Machining strategy can significantly influence surface integrity when producing holes in CFRP laminate, which has drastic impact on mechanical behavior and service life of related structures. Therefore, it is vital to understand the effect of defects caused by machining on cracking/splitting initiation, propagation and final failure modes. In this paper, the influence of four different machining processes used to produce 6.0 mm diameter holes in CFRP was investigated in relation to mechanical behaviour under tensile loading. The processes involved were high power fiber laser cutting, abrasive waterjet machining, conventional drilling and ultraviolet laser multiple-pass machining. The complex strain distributions around the holes were analyzed using digital image correlation (DIC) method, while crack propagation was studied using high speed imaging technique. The correlation between initial surface integrity and mechanical behavior was developed. Stress concentrations and machining defects around holes accelerated damage accumulation with final failure modes highly related to fiber orientations rather than initial surface damage.