Selection of critical thermal/structural design parameters for a metal/composite joint in a composite electronics enclosure

An experiment was designed to determine the critical design parameters for a metal/composite joint in a composite electronic enclosure where both thermal and mechanical performance are important. A combination bolted and bonded single-lap joint that simulates the interface between the thermal wall and the card guide was studied under static loading with power supplied through a surface-mounted chip resistor. The following parameters were varied: fiber orientation, type of thermally conductive pitch fiber, type of adhesive, adhesive thickness. bolt spacing, bolt size, and input power. Load, strain, and temperature from five thermocouples were collected during a tensile test with a 0.02 in/min. strain rate. A fractional factorial experimental design was used. A dual failure mechanism was consistently recorded: failure of the adhesive bond followed by bolt shear failure. Initial screening results indicated that a configuration can be achieved that significantly enhances both mechanical and thermal performance.