ISO 15310:1999

Overview

ISO 15310:1999 specifies the plate twist method for determining the in‑plane shear modulus (G12) of fibre‑reinforced plastic composites. The method uses a square plate specimen supported on two points on one diagonal and loaded on the opposite diagonal by two loading points attached to a cross‑beam. It measures the low‑strain shear modulus (not shear strength) and is applicable to composites with thermoset or thermoplastic matrices, and can also be applied to unreinforced polymers and other materials when appropriate.

Key topics and technical requirements

• Measured property: in‑plane shear modulus G12 (expressed in GPa), determined between plate deflections of 0.1h and 0.3h (h = plate thickness).
• Specimen geometry: square, flat plates. Standard widths a′, a″ = 150 mm with thickness ranges specified (e.g., discontinuous/fabric/multidirectional ~4 ± 0.5 mm; unidirectional ~2 ± 0.5 mm). Span S is calculated as S = 0.95·D (D = diagonal length).
• Test arrangement: supports on two points on one diagonal, simultaneous loading on the other diagonal via a rigid cross‑beam (plate twist method). Support/loading point radius = 2.0 mm ± 0.2 mm.
• Test conditions: speed of testing 1 mm/min ± 20%; record load vs deflection and determine modulus from loads at w = 0.1h and w = 0.3h. Use geometric correction factor K (standard value K = 0.822 for S/D = 0.95; formula provided for other ratios).
• Limitations and preparation: determines modulus at low shear strains only (stress–strain is non‑linear at higher strains). Specimens must be flat, free of defects, and approximately homogeneous through the thickness; principal material axes (if present) must be normal to plate edges. Conditioning, specimen preparation and dimensions must be controlled for comparable data.
• Precision and statistics: test at least five specimens; compute mean, standard deviation, and confidence intervals per ISO 2602.

Applications and who uses it

• Materials and composites test laboratories performing shear characterization.
• R&D and design engineers needing G12 input for finite element models and laminate analysis.
• Quality control teams comparing batches or verifying material specifications.
• Manufacturers of fibre‑reinforced plastics (thermoset and thermoplastic) and suppliers validating laminate properties.
• Useful for benchmarking materials, validating lay‑up homogeneity, and supporting engineering design where in‑plane shear stiffness is critical (e.g., aerospace, automotive, sporting goods).

Related standards

Normative references cited in ISO 15310:1999 include:

• ISO 291 (conditioning)
• ISO 1268 (specimen preparation)
• ISO 2818 (machining specimens)
• ISO 5893 (test equipment)
• ISO 2602 (statistical interpretation)

Keywords: ISO 15310:1999, plate twist method, in‑plane shear modulus, G12, fibre‑reinforced plastic composites, shear testing, composite test standard.