In the aviation and aerospace industries, devices and their package structures consist of a variety of metallic, ceramic, plastic, or composite components with vastly different coefficients of thermal expansion (CTE). Mechanical failures in such devices can be caused by thermal expansion mismatch among the materials during fabrication or service.
Lightweight thermoplastic materials (e.g., thermoplastic foams) are commonly applied in the aerospace and aviation industries to the manufacture of ducts, seals, and other components. These materials have a characteristically higher CTE than the surrounding structural elements to which the thermoplastic components are connected. For example, thermoplastic foams typically have a CTE of about 75-150×10−6/° F. (or 75-150 μ/° F.), and other thermoplastics (e.g., nylon, ABS, PVC) typically have a CTE of about 30-60 μ/° F., as compared to other common system materials, such as aluminum (about 13 μ/° F.) and steel (about 7 μ/° F.). A problem that may arise is thermally induced stress transferred to adjacent components with mismatched CTE. While mismatched expansion or contraction of thermoplastic parts may be mitigated by bonding these parts along their entire length to an adjacent structure with lower CTE, such attachment may cause the thermoplastic part to become anisotropic or demonstrate a weak axis of bending, which could cause the thermoplastic part to warp or otherwise deform through normal handling and use.