THERMAL EFFECTS ON THE COMPRESSIVEBEHAVIOR OF IM7/PETI5 LAMINATES

摘要

The effect of changing operating temperature on the compressive response of IM7/PETI5composite laminates is investigated within this paper. The three temperatures evaluated for thisstudy were –129oC, 21oC, and 177oC, a spectrum from cryogenic to an elevated operatingtemperature. Laminate compressive strength property testing was conducted using the WyomingCombined Load Compression fixture to generate strength data at the three operating temperaturesof interest for several lay-ups. A three-dimensional finite element analysis model of a [90/0]8scomposite laminate subject to compressive loading is developed. The model is used to study thekey attributes of the laminate that significantly influence the state of stress in the laminate. Boththe resin rich layer located between lamina and the thermal residual stresses present in thelaminate due to curing are included in the analysis model. For the laminate modeled, the effect ofmodeling temperature dependent material properties was determined to be insignificant for theoperating temperatures studied. Simply using the material properties measured at the operatingtemperature of interest was sufficient for predicting stresses accurately in a linear analysis for thecurrent problem. The three-dimensional analysis results revealed that the application of anapplied compressive axial load in the 0-degree direction decreased the interlaminar stressespresent in the laminate initially due to curing. Therefore, failure was concluded not beattributable to the interlaminar stresses in the composite laminate being studied when acompressive load is applied. The magnitude of the measured laminate compressive strengthchange with a change in temperature is concluded to be dominated by the change in the laminacompressive axial strength with a change in temperature.