This paper presents an effective and reliable non-destructive method to measure the Young Modulus of porous and out of plane Young Modulus of composite materials using sound waves. First, a Finite Element Model based on Representative Volume Element (RVE) is developed to demonstrate how the elastic properties of composite material can be estimated by acoustic measurements using an impedance tube test rig. Second, the results of the experimental measurement campaign was carried out to validate the proposed method. In particular, two soft elastic foams with different density, an epoxy-carbon fibre composite and vynilester-glass fibre composite were tested. In the proposed method, a two-microphone impedance tube setup was used where the measured acoustic pressures at two upstream locations allowed the estimation of the reflection coefficient and the acoustic impedance of the tested materials. Since the acoustic impedance can be expressed as a function of the longitudinal speed of sound (assuming a plane standing wave excitation), the elastic modulus can be estimated which is associated with the speed of sound. The elastic modulus measured using the proposed method were in good agreement with the values obtained by the standard methods such as tensile tests and ultrasound time of flight measurements. The proposed method would allow in an accurate and fast manner the non-destructive evaluation of Young Modulus of porous materials and for the first time the proposed approach is applied successfully to the measurement of out of plane Young modulus of composite materials.

本文提出了一种有效且可靠的无损方法，利用声波来测量复合材料的多孔杨氏模量和平面外杨氏模量。首先，开发了基于代表性体积元素（RVE）的有限元模型，以演示如何通过使用阻抗管测试台进行声学测量来估计复合材料的弹性性能。其次，进行了实验测量活动的结果以验证所提出的方法。特别地，测试了两种具有不同密度的软弹性泡沫，环氧-碳纤维复合材料和维尼斯特尔-玻璃纤维复合材料。在建议的方法中，使用两个麦克风的阻抗管装置，其中在两个上游位置测得的声压允许估计反射系数和被测材料的声阻抗。由于声阻抗可以表示为声音的纵向速度的函数（假设为平面驻波激励），因此可以估算与声音速度相关的弹性模量。使用建议的方法测量的弹性模量与通过标准方法（例如拉伸试验和超声飞行时间测量）获得的值高度吻合。