Composite Materials Engineering, Volume 1 by Xiao-Su Yi Shanyi Du & Litong Zhang

Author:Xiao-Su Yi, Shanyi Du & Litong Zhang
Language: eng
Format: epub
Publisher: Springer Singapore, Singapore

4.5 Building Block Approach for Composite Structure Design Verification

4.5.1 Introduction and Philosophy

Owing to the lack of effective analysis and extensive design and use the experience of composite structures the structural integrity needs to be ensured in some way [1–3]. The BBA consists of multiple level testing and certification, at the level of coupons, structural elements, subcomponents, components, and finally a complete full-scale product. This approach is used to solve (and certify) challenging issues such as environmental effects and damage. This approach can also reduce the complexity of full-size tests, qualify the safety of cost reduction measures, and ensure a pass on full-size verification.

For widely used composite/metal structures, the BBA verification approach can also be applied for testing below the substructure component level, and used to complement verification of composite durability and damage tolerance.

For the static strength verification tests of full-size parts, it is difficult to simulate a full range of combined ambient effects, thus the verification may not be fully comprehensive. However, the overall integration can be guaranteed for composite structure static verification, if a BBA verification test program is properly organized.

On the basis of the maturity of materials and design, and the accumulation of experience, the testing content and coupon numbers may be reduced to decrease development costs.

The application of the BBA has not yet been standardized. Relationships between numbers of specimens and material bases values are well defined for specimen tests at the lowest level (see part 15), the numbers of specimens required at higher levels of complexity are somewhat arbitrary and largely based on historical experience, structural criticality, engineering judgment, and economic considerations. Thus, there is currently no standardized methodology for statistically validating each level of the process, although some attempts have been made to develop models that relate specimen quantities to overall reliability.

The sensitivity to out-of-plane loads, failure mode multiplicity, sensitivity to ambient operation conditions, and the absence of mature and reliable analysis for comparing composite and metal structures, motivate the use BBA for structural certification of composite structures [1–3].

The multiplicity of potential failure modes is perhaps the main reason that the BBA is essential for the development of composite structural substantiation. The many failure modes in composite structures are mainly caused by defects, environmental effects, and out-of-plane sensitivities of the materials.

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