A study on dimensional deviations in manufacturing process of carbon fiber reinforced composite aerial structures

CFRP parts, particularly those used in primary structures in the aviation industry, often deviate from their designed geometries after the production process. This difference results in significant cost losses during structural assembly activities or poses a threat to flight safety throughout the operational phases of the aircraft. The literature indicates types of divergence from designed geometry that depend on the part shape and the classification of intrinsic and extrinsic factors affecting these deformations. In this study, deformation calculations were conducted using analytical methods reported in the literature for an L-shaped test piece, made of AS4/8552 composite material, predicting the deformation due to intrinsic factors. In the experimental phase, four molds were prepared using four different tool materials to produce 24 test specimens while keeping the intrinsic factors constant. In addition to the PID caused by these intrinsic factors, the analytical formulation was expanded to encompass mold parameters, regarded as extrinsic factors. Depending on the linear thermal expansion coefficient of tool material ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>α</mml:mi> <mml:mrow> <mml:mi>C</mml:mi> <mml:mi>T</mml:mi> <mml:mi>E</mml:mi> </mml:mrow> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> in µm/m-°C, an increase of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mrow> <mml:mn>0.1148</mml:mn> <mml:mo> </mml:mo> <mml:mi>ln</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>α</mml:mi> <mml:mrow> <mml:mi>C</mml:mi> <mml:mi>T</mml:mi> <mml:mi>E</mml:mi> </mml:mrow> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.0387</mml:mn> </mml:mrow> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> is required to converge to experimental result for male tooling where an increase of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mrow> <mml:mn>0.1333</mml:mn> <mml:mo> </mml:mo> <mml:mi>ln</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>α</mml:mi> <mml:mrow> <mml:mi>C</mml:mi> <mml:mi>T</mml:mi> <mml:mi>E</mml:mi> </mml:mrow> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.0626</mml:mn> </mml:mrow> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> is necessary in female tooling. The deformation differences coming from the parts with identical intrinsic parameters in male and female molds were compared. The results showed that 10% to 18% angular deformation increase in female tooling over male tooling. A mold compensation factor calculation method is proposed for use in the design phase of the tools to help achieve alignment with the part design geometries.