A nanocomposite strategy for the selective inclusion of viscoelastic polyethylene into TPU fiber junctions is demonstrated to create effective stress-transfer pathways within three-dimensional (3-D) fiber-reinforced polyethylene-based composites with a phenomenal thermal insulation properties. Inspired by the bone architecture in the human body, large amounts of hard segments and small amounts of soft segments, the 3-D interconnected TPU-polyethylene composite achieves synergistic strengthening. The composite is prepared by a wet chemical synthesis approach, a sol–gel reaction, with operation procedure of polyethylene while incorporating TPU fiber phase. The solution containing polyethylene precursor initiates network formation throughout the liquid to form a 3-D network (the gel) through chain polymerization. The obtained polyethylene-based gel reinforced with TPU fibers is then left to be aged stimulated by time and temperature for structure completion. By the end of aging process, the solvent is extracted from the gels through supercritical drying technique. The remained obtained solid structure is the TPU-PE composite nanocellular foam structure. The resulting TPU-PE composite exhibited fully structural deformations and compressive mechanical strength (18 MPa at a compressive strain of 90%) at one compression cycle while showing an extremely low thermal conductivity of 13.9 mW/m.K (lower than intrinsic thermal conductivity of the solid material). Owing to the combination of excellent mechanical and thermal insulation properties, the TPU-PE composite can be used as thermal insulation material for strain sensors, showing very short response and load bearing with reliable sensitivity and extreme durability. Such bio-inspired architecture opens the door to fabricate new 3-D-multifunctional and mechanically durable nano-composite for thermal insulation products and strong partially-flexible devices.