Document ID: APP-C365
Public Compliance Release

ASTM C365 Test Guide: Compression Testing for Composites

Architecture
NEWTON™ 32-BIT

Application Details

Standard:
ASTM C365
Material Type:
Composites
Specimen Type:
Test Type:
Compression
Industry:
Aerospace
Mechanicaltest.org | Applications

The Challenge Gap

Specimen edge burrs and non-parallel core surfaces introduce localized crushing artifacts, inflating initial displacement metrics.

The Solution

Utilize a spherical seat self-aligning upper compression platen paired with direct-on-sample extensometers or LVDTs.

Insight

Always use a direct-contact deflectometer setup to measure core deflection; crosshead travel includes platen-seating errors.

Required Test Equipment for ASTM C365

Software

Driven by the Newton N-C365 software module to compute flatwise compressive strength, core compressive modulus, and structural core deformation metrics.

Grips/Fixtures

Features high-stiffness, parallel compression platens engineered to apply uniform flatwise loading across the entire sandwich core surface.

Extensometer

Equipped with a high-accuracy, direct-contact deflectometer measuring absolute platen-to-platen travel, bypassing frame compliance errors.

Insight

Always use a direct-contact deflectometer setup to measure core deflection; crosshead travel includes platen-seating errors.

The Newton Advantage

Synchronous 32-bit hardware layer samples the direct-contact deflectometer natively, bypassing frame compliance error completely.

Expert Engineering Commentary

Core Problem Identification

Artificial softening on the initial stress-strain slope caused by the compression platens seating against uneven cell walls.

Root Cause Analysis

Minor macro-surface waves across the core sample face creating non-simultaneous contact across the platen area.

Hardware Specific Solutions

Hardened steel compression platens with an integrated sub-press spherical alignment seat and a direct-deflection displacement cage.

Mechanics & Specimen Behavior

Primary Mechanics

Out-of-plane vertical compressive force applied to sandwich cores to determine core crushing strength and compressive modulus.

Specimen Details

Square or circular core block, typical dimensions measuring 50mm x 50mm, with unbonded or bonded facings.

Mechanical Ratios & Properties

Surface area to core thickness ratios optimized per standard to prevent structural column instability during cell crushing.

Additional Commentary

Direct displacement tracking captures the true elastic deformation slope of delicate cell walls without systemic compliance noise.

Pro Tip

Ensure honeycomb core cell axes are aligned perfectly parallel to the loading vector to capture true out-of-plane strength.

Common Pitfalls

Ignoring the initial non-linear toe region of the load curve instead of performing a proper mathematical toe-compensation correction.

Analysis & Calculation Standards

Event & Failure Detection
Initial touch-point contact force auto-zeroing followed by multi-stage proportional crush-limit termination thresholds.
Required Calculations
Flatwise Compressive Strength, Core Compressive Modulus, Compressive Stress at Specified Strain, and Ultimate Crush Force.
Statistical Outputs
Production batch averages, cell-collapse plateau analysis tracking, standard deviations, and lot conformance profiles.
Let's Find the Right ASTM C365 Equipment for Your Application

The Newton™ 32-Bit
Difference

Typical testing system controllers rely on 24-bit resolution. Under high-accuracy flexural analysis, this creates a data phenomenon called **”stair-stepping”** or quantization error. When trying to track minor micro-deflection in rigid polymers, 24-bit electronic circuits suffer from resolution limits, dropping critical transition points during initial load curves.

Newton Characterization™ architecture utilizes a 32-bit analog-to-digital processor converter. This increases measurement fidelity by a factor of 256x, outputting 4.29 billion discrete signal thresholds. Electrical chatter is actively muted under a dedicated 100,000:1 Signal-to-Noise Ratio (SNR).

Simulate Signal Mode

Real-Time Continuous Sampling Simulation

Comparing standard 24-bit quantization with Newton™ 32-bit resolution

Observe the stepped resolution blocks in the legacy 24-bit curve (Red) versus the absolute **analog-smooth response curve** captured by Newton™ 32-bit architectures (Green). This fidelity is what prevents mechanical data variance during modulus evaluation.

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