The Datasheet Is Not the Structure: Why laboratory performance does not automatically become real-world performance

Laboratory testing is indispensable because it allows material and product properties to be measured under defined, repeatable and comparable conditions. The engineering problem begins when evidence established at one level is extended to a higher-level performance claim without adequate justification. This technical note examines that transfer problem and proposes a six-level Performance-Transfer Framework, a Performance Evidence Ladder and an Evidence–Claim Matching Principle linking material properties, component behaviour, interfaces, assemblies, as-built verification and in-use performance. The framework does not diminish laboratory testing; it clarifies the domain of validity of evidence and the engineering routes required when claims extend beyond that domain.