AA-SB-001: Analysis And Design Of Composite And Metallic Flight Vehicle Structures

Third Edition

6.3. Section Properties of a Composite Shape

Reference: Abbott, Richard. Analysis and Design of Composite and Metallic Flight Vehicle Structures 3 Edition, 2019

More complex shapes can be built up from individual rectangular sections. The section property can be calculated for each rectangle and the combined section property calculated for the combination.

The section properties of a composite shape are defined as follows:

The total second moment of area of the shape is determined by using the parallel axis theorem (see section 6.1.4) with I’ being the 2nd moment of area of each individual component:

The solution is best laid out as a table, with a row for each element of the cross section. This is shown in the spreadsheet at the link below:

AA-SM-001-002 Section Properties – General

The spreadsheet first calculates the combined section properties about the origin:

Figure 6.1.5‑1: Tabular Calculation of Combined Section Properties about Origin

 This table is used to determine the centroid of the combined rectangles.

The spreadsheet then recalculates the section properties about the centroid of the combined rectangles:

Figure 6.1.5‑2: Tabular Calculation of Combined Section Properties about Section Centroidal Axis

There are different spreadsheets that allow analysis of various composite rectangular sections at the links below:

AA-SM-001-004 Section Properties – General with Angles –
moment distribution
AA-SM-001-005 Section Properties – General with Angles –
Really Small Format
AA-SM-001-006 Section Properties – General with Angles –
Weighted area – moment distribution
AA-SM-001-007 Section Properties – General with Angles –
weighted area – moment distribution – small format

6.3. Section Properties of a Composite Shape

Reference: Abbott, Richard. Analysis and Design of Composite and Metallic Flight Vehicle Structures 3 Edition, 2019

More complex shapes can be built up from individual rectangular sections. The section property can be calculated for each rectangle and the combined section property calculated for the combination.

The section properties of a composite shape are defined as follows:

The total second moment of area of the shape is determined by using the parallel axis theorem (see section 6.1.4) with I’ being the 2nd moment of area of each individual component:

The solution is best laid out as a table, with a row for each element of the cross section. This is shown in the spreadsheet at the link below:

AA-SM-001-002 Section Properties – General

The spreadsheet first calculates the combined section properties about the origin:

Figure 6.1.5‑1: Tabular Calculation of Combined Section Properties about Origin

 This table is used to determine the centroid of the combined rectangles.

The spreadsheet then recalculates the section properties about the centroid of the combined rectangles:

Figure 6.1.5‑2: Tabular Calculation of Combined Section Properties about Section Centroidal Axis

There are different spreadsheets that allow analysis of various composite rectangular sections at the links below:

AA-SM-001-004 Section Properties – General with Angles –
moment distribution
AA-SM-001-005 Section Properties – General with Angles –
Really Small Format
AA-SM-001-006 Section Properties – General with Angles –
Weighted area – moment distribution
AA-SM-001-007 Section Properties – General with Angles –
weighted area – moment distribution – small format